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linux/arch/x86/Kconfig
Kees Cook d6f635bcac x86/alternatives: Make FineIBT mode Kconfig selectable 
Since FineIBT performs checking at the destination, it is weaker against
attacks that can construct arbitrary executable memory contents. As such,
some system builders want to run with FineIBT disabled by default. Allow
the "cfi=kcfi" boot param mode to be selectable through Kconfig via the
newly introduced CONFIG_CFI_AUTO_DEFAULT.

Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20240501000218.work.998-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
2024-06-19 12:41:08 -07:00

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# SPDX-License-Identifier: GPL-2.0
# Select 32 or 64 bit
config 64BIT
bool "64-bit kernel" if "$(ARCH)" = "x86"
default "$(ARCH)" != "i386"
help
Say yes to build a 64-bit kernel - formerly known as x86_64
Say no to build a 32-bit kernel - formerly known as i386
config X86_32
def_bool y
depends on !64BIT
# Options that are inherently 32-bit kernel only:
select ARCH_WANT_IPC_PARSE_VERSION
select CLKSRC_I8253
select CLONE_BACKWARDS
select GENERIC_VDSO_32
select HAVE_DEBUG_STACKOVERFLOW
select KMAP_LOCAL
select MODULES_USE_ELF_REL
select OLD_SIGACTION
select ARCH_SPLIT_ARG64
config X86_64
def_bool y
depends on 64BIT
# Options that are inherently 64-bit kernel only:
select ARCH_HAS_GIGANTIC_PAGE
select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
select ARCH_SUPPORTS_PER_VMA_LOCK
select HAVE_ARCH_SOFT_DIRTY
select MODULES_USE_ELF_RELA
select NEED_DMA_MAP_STATE
select SWIOTLB
select ARCH_HAS_ELFCORE_COMPAT
select ZONE_DMA32
select EXECMEM if DYNAMIC_FTRACE
config FORCE_DYNAMIC_FTRACE
def_bool y
depends on X86_32
depends on FUNCTION_TRACER
select DYNAMIC_FTRACE
help
We keep the static function tracing (!DYNAMIC_FTRACE) around
in order to test the non static function tracing in the
generic code, as other architectures still use it. But we
only need to keep it around for x86_64. No need to keep it
for x86_32. For x86_32, force DYNAMIC_FTRACE.
#
# Arch settings
#
# ( Note that options that are marked 'if X86_64' could in principle be
# ported to 32-bit as well. )
#
config X86
def_bool y
#
# Note: keep this list sorted alphabetically
#
select ACPI_LEGACY_TABLES_LOOKUP if ACPI
select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
select ACPI_HOTPLUG_CPU if ACPI_PROCESSOR && HOTPLUG_CPU
select ARCH_32BIT_OFF_T if X86_32
select ARCH_CLOCKSOURCE_INIT
select ARCH_CONFIGURES_CPU_MITIGATIONS
select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64
select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG
select ARCH_ENABLE_SPLIT_PMD_PTLOCK if (PGTABLE_LEVELS > 2) && (X86_64 || X86_PAE)
select ARCH_ENABLE_THP_MIGRATION if X86_64 && TRANSPARENT_HUGEPAGE
select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
select ARCH_HAS_CACHE_LINE_SIZE
select ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION
select ARCH_HAS_CPU_FINALIZE_INIT
select ARCH_HAS_CPU_PASID if IOMMU_SVA
select ARCH_HAS_CURRENT_STACK_POINTER
select ARCH_HAS_DEBUG_VIRTUAL
select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
select ARCH_HAS_DEVMEM_IS_ALLOWED
select ARCH_HAS_EARLY_DEBUG if KGDB
select ARCH_HAS_ELF_RANDOMIZE
select ARCH_HAS_FAST_MULTIPLIER
select ARCH_HAS_FORTIFY_SOURCE
select ARCH_HAS_GCOV_PROFILE_ALL
select ARCH_HAS_KCOV if X86_64
select ARCH_HAS_KERNEL_FPU_SUPPORT
select ARCH_HAS_MEM_ENCRYPT
select ARCH_HAS_MEMBARRIER_SYNC_CORE
select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
select ARCH_HAS_PMEM_API if X86_64
select ARCH_HAS_PTE_DEVMAP if X86_64
select ARCH_HAS_PTE_SPECIAL
select ARCH_HAS_HW_PTE_YOUNG
select ARCH_HAS_NONLEAF_PMD_YOUNG if PGTABLE_LEVELS > 2
select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
select ARCH_HAS_COPY_MC if X86_64
select ARCH_HAS_SET_MEMORY
select ARCH_HAS_SET_DIRECT_MAP
select ARCH_HAS_STRICT_KERNEL_RWX
select ARCH_HAS_STRICT_MODULE_RWX
select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
select ARCH_HAS_SYSCALL_WRAPPER
select ARCH_HAS_UBSAN
select ARCH_HAS_DEBUG_WX
select ARCH_HAS_ZONE_DMA_SET if EXPERT
select ARCH_HAVE_NMI_SAFE_CMPXCHG
select ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
select ARCH_MIGHT_HAVE_PC_PARPORT
select ARCH_MIGHT_HAVE_PC_SERIO
select ARCH_STACKWALK
select ARCH_SUPPORTS_ACPI
select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_SUPPORTS_DEBUG_PAGEALLOC
select ARCH_SUPPORTS_PAGE_TABLE_CHECK if X86_64
select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
select ARCH_SUPPORTS_CFI_CLANG if X86_64
select ARCH_USES_CFI_TRAPS if X86_64 && CFI_CLANG
select ARCH_SUPPORTS_LTO_CLANG
select ARCH_SUPPORTS_LTO_CLANG_THIN
select ARCH_USE_BUILTIN_BSWAP
select ARCH_USE_CMPXCHG_LOCKREF if X86_CMPXCHG64
select ARCH_USE_MEMTEST
select ARCH_USE_QUEUED_RWLOCKS
select ARCH_USE_QUEUED_SPINLOCKS
select ARCH_USE_SYM_ANNOTATIONS
select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
select ARCH_WANTS_DYNAMIC_TASK_STRUCT
select ARCH_WANTS_NO_INSTR
select ARCH_WANT_GENERAL_HUGETLB
select ARCH_WANT_HUGE_PMD_SHARE
select ARCH_WANT_LD_ORPHAN_WARN
select ARCH_WANT_OPTIMIZE_DAX_VMEMMAP if X86_64
select ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP if X86_64
select ARCH_WANTS_THP_SWAP if X86_64
select ARCH_HAS_PARANOID_L1D_FLUSH
select BUILDTIME_TABLE_SORT
select CLKEVT_I8253
select CLOCKSOURCE_VALIDATE_LAST_CYCLE
select CLOCKSOURCE_WATCHDOG
# Word-size accesses may read uninitialized data past the trailing \0
# in strings and cause false KMSAN reports.
select DCACHE_WORD_ACCESS if !KMSAN
select DYNAMIC_SIGFRAME
select EDAC_ATOMIC_SCRUB
select EDAC_SUPPORT
select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
select GENERIC_CLOCKEVENTS_BROADCAST_IDLE if GENERIC_CLOCKEVENTS_BROADCAST
select GENERIC_CLOCKEVENTS_MIN_ADJUST
select GENERIC_CMOS_UPDATE
select GENERIC_CPU_AUTOPROBE
select GENERIC_CPU_DEVICES
select GENERIC_CPU_VULNERABILITIES
select GENERIC_EARLY_IOREMAP
select GENERIC_ENTRY
select GENERIC_IOMAP
select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
select GENERIC_IRQ_MIGRATION if SMP
select GENERIC_IRQ_PROBE
select GENERIC_IRQ_RESERVATION_MODE
select GENERIC_IRQ_SHOW
select GENERIC_PENDING_IRQ if SMP
select GENERIC_PTDUMP
select GENERIC_SMP_IDLE_THREAD
select GENERIC_TIME_VSYSCALL
select GENERIC_GETTIMEOFDAY
select GENERIC_VDSO_TIME_NS
select GENERIC_VDSO_OVERFLOW_PROTECT
select GUP_GET_PXX_LOW_HIGH if X86_PAE
select HARDIRQS_SW_RESEND
select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
select HAS_IOPORT
select HAVE_ACPI_APEI if ACPI
select HAVE_ACPI_APEI_NMI if ACPI
select HAVE_ALIGNED_STRUCT_PAGE
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
select HAVE_ARCH_HUGE_VMALLOC if X86_64
select HAVE_ARCH_JUMP_LABEL
select HAVE_ARCH_JUMP_LABEL_RELATIVE
select HAVE_ARCH_KASAN if X86_64
select HAVE_ARCH_KASAN_VMALLOC if X86_64
select HAVE_ARCH_KFENCE
select HAVE_ARCH_KMSAN if X86_64
select HAVE_ARCH_KGDB
select HAVE_ARCH_MMAP_RND_BITS if MMU
select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
select HAVE_ARCH_PREL32_RELOCATIONS
select HAVE_ARCH_SECCOMP_FILTER
select HAVE_ARCH_THREAD_STRUCT_WHITELIST
select HAVE_ARCH_STACKLEAK
select HAVE_ARCH_TRACEHOOK
select HAVE_ARCH_TRANSPARENT_HUGEPAGE
select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
select HAVE_ARCH_VMAP_STACK if X86_64
select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
select HAVE_ARCH_WITHIN_STACK_FRAMES
select HAVE_ASM_MODVERSIONS
select HAVE_CMPXCHG_DOUBLE
select HAVE_CMPXCHG_LOCAL
select HAVE_CONTEXT_TRACKING_USER if X86_64
select HAVE_CONTEXT_TRACKING_USER_OFFSTACK if HAVE_CONTEXT_TRACKING_USER
select HAVE_C_RECORDMCOUNT
select HAVE_OBJTOOL_MCOUNT if HAVE_OBJTOOL
select HAVE_OBJTOOL_NOP_MCOUNT if HAVE_OBJTOOL_MCOUNT
select HAVE_BUILDTIME_MCOUNT_SORT
select HAVE_DEBUG_KMEMLEAK
select HAVE_DMA_CONTIGUOUS
select HAVE_DYNAMIC_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_REGS
select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
select HAVE_EBPF_JIT
select HAVE_EFFICIENT_UNALIGNED_ACCESS
select HAVE_EISA
select HAVE_EXIT_THREAD
select HAVE_GUP_FAST
select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_GRAPH_TRACER if X86_32 || (X86_64 && DYNAMIC_FTRACE)
select HAVE_FUNCTION_TRACER
select HAVE_GCC_PLUGINS
select HAVE_HW_BREAKPOINT
select HAVE_IOREMAP_PROT
select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
select HAVE_IRQ_TIME_ACCOUNTING
select HAVE_JUMP_LABEL_HACK if HAVE_OBJTOOL
select HAVE_KERNEL_BZIP2
select HAVE_KERNEL_GZIP
select HAVE_KERNEL_LZ4
select HAVE_KERNEL_LZMA
select HAVE_KERNEL_LZO
select HAVE_KERNEL_XZ
select HAVE_KERNEL_ZSTD
select HAVE_KPROBES
select HAVE_KPROBES_ON_FTRACE
select HAVE_FUNCTION_ERROR_INJECTION
select HAVE_KRETPROBES
select HAVE_RETHOOK
select HAVE_LIVEPATCH if X86_64
select HAVE_MIXED_BREAKPOINTS_REGS
select HAVE_MOD_ARCH_SPECIFIC
select HAVE_MOVE_PMD
select HAVE_MOVE_PUD
select HAVE_NOINSTR_HACK if HAVE_OBJTOOL
select HAVE_NMI
select HAVE_NOINSTR_VALIDATION if HAVE_OBJTOOL
select HAVE_OBJTOOL if X86_64
select HAVE_OPTPROBES
select HAVE_PAGE_SIZE_4KB
select HAVE_PCSPKR_PLATFORM
select HAVE_PERF_EVENTS
select HAVE_PERF_EVENTS_NMI
select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
select HAVE_PCI
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP
select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
select MMU_GATHER_MERGE_VMAS
select HAVE_POSIX_CPU_TIMERS_TASK_WORK
select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_RELIABLE_STACKTRACE if UNWINDER_ORC || STACK_VALIDATION
select HAVE_FUNCTION_ARG_ACCESS_API
select HAVE_SETUP_PER_CPU_AREA
select HAVE_SOFTIRQ_ON_OWN_STACK
select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
select HAVE_STACK_VALIDATION if HAVE_OBJTOOL
select HAVE_STATIC_CALL
select HAVE_STATIC_CALL_INLINE if HAVE_OBJTOOL
select HAVE_PREEMPT_DYNAMIC_CALL
select HAVE_RSEQ
select HAVE_RUST if X86_64
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_UACCESS_VALIDATION if HAVE_OBJTOOL
select HAVE_UNSTABLE_SCHED_CLOCK
select HAVE_USER_RETURN_NOTIFIER
select HAVE_GENERIC_VDSO
select HOTPLUG_PARALLEL if SMP && X86_64
select HOTPLUG_SMT if SMP
select HOTPLUG_SPLIT_STARTUP if SMP && X86_32
select IRQ_FORCED_THREADING
select LOCK_MM_AND_FIND_VMA
select NEED_PER_CPU_EMBED_FIRST_CHUNK
select NEED_PER_CPU_PAGE_FIRST_CHUNK
select NEED_SG_DMA_LENGTH
select PCI_DOMAINS if PCI
select PCI_LOCKLESS_CONFIG if PCI
select PERF_EVENTS
select RTC_LIB
select RTC_MC146818_LIB
select SPARSE_IRQ
select SYSCTL_EXCEPTION_TRACE
select THREAD_INFO_IN_TASK
select TRACE_IRQFLAGS_SUPPORT
select TRACE_IRQFLAGS_NMI_SUPPORT
select USER_STACKTRACE_SUPPORT
select HAVE_ARCH_KCSAN if X86_64
select PROC_PID_ARCH_STATUS if PROC_FS
select HAVE_ARCH_NODE_DEV_GROUP if X86_SGX
select FUNCTION_ALIGNMENT_16B if X86_64 || X86_ALIGNMENT_16
select FUNCTION_ALIGNMENT_4B
imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
config INSTRUCTION_DECODER
def_bool y
depends on KPROBES || PERF_EVENTS || UPROBES
config OUTPUT_FORMAT
string
default "elf32-i386" if X86_32
default "elf64-x86-64" if X86_64
config LOCKDEP_SUPPORT
def_bool y
config STACKTRACE_SUPPORT
def_bool y
config MMU
def_bool y
config ARCH_MMAP_RND_BITS_MIN
default 28 if 64BIT
default 8
config ARCH_MMAP_RND_BITS_MAX
default 32 if 64BIT
default 16
config ARCH_MMAP_RND_COMPAT_BITS_MIN
default 8
config ARCH_MMAP_RND_COMPAT_BITS_MAX
default 16
config SBUS
bool
config GENERIC_ISA_DMA
def_bool y
depends on ISA_DMA_API
config GENERIC_CSUM
bool
default y if KMSAN || KASAN
config GENERIC_BUG
def_bool y
depends on BUG
select GENERIC_BUG_RELATIVE_POINTERS if X86_64
config GENERIC_BUG_RELATIVE_POINTERS
bool
config ARCH_MAY_HAVE_PC_FDC
def_bool y
depends on ISA_DMA_API
config GENERIC_CALIBRATE_DELAY
def_bool y
config ARCH_HAS_CPU_RELAX
def_bool y
config ARCH_HIBERNATION_POSSIBLE
def_bool y
config ARCH_SUSPEND_POSSIBLE
def_bool y
config AUDIT_ARCH
def_bool y if X86_64
config KASAN_SHADOW_OFFSET
hex
depends on KASAN
default 0xdffffc0000000000
config HAVE_INTEL_TXT
def_bool y
depends on INTEL_IOMMU && ACPI
config X86_64_SMP
def_bool y
depends on X86_64 && SMP
config ARCH_SUPPORTS_UPROBES
def_bool y
config FIX_EARLYCON_MEM
def_bool y
config DYNAMIC_PHYSICAL_MASK
bool
config PGTABLE_LEVELS
int
default 5 if X86_5LEVEL
default 4 if X86_64
default 3 if X86_PAE
default 2
config CC_HAS_SANE_STACKPROTECTOR
bool
default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC) $(CLANG_FLAGS)) if 64BIT
default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC) $(CLANG_FLAGS))
help
We have to make sure stack protector is unconditionally disabled if
the compiler produces broken code or if it does not let us control
the segment on 32-bit kernels.
menu "Processor type and features"
config SMP
bool "Symmetric multi-processing support"
help
This enables support for systems with more than one CPU. If you have
a system with only one CPU, say N. If you have a system with more
than one CPU, say Y.
If you say N here, the kernel will run on uni- and multiprocessor
machines, but will use only one CPU of a multiprocessor machine. If
you say Y here, the kernel will run on many, but not all,
uniprocessor machines. On a uniprocessor machine, the kernel
will run faster if you say N here.
Note that if you say Y here and choose architecture "586" or
"Pentium" under "Processor family", the kernel will not work on 486
architectures. Similarly, multiprocessor kernels for the "PPro"
architecture may not work on all Pentium based boards.
People using multiprocessor machines who say Y here should also say
Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
Management" code will be disabled if you say Y here.
See also <file:Documentation/arch/x86/i386/IO-APIC.rst>,
<file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
<http://www.tldp.org/docs.html#howto>.
If you don't know what to do here, say N.
config X86_X2APIC
bool "Support x2apic"
depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
help
This enables x2apic support on CPUs that have this feature.
This allows 32-bit apic IDs (so it can support very large systems),
and accesses the local apic via MSRs not via mmio.
Some Intel systems circa 2022 and later are locked into x2APIC mode
and can not fall back to the legacy APIC modes if SGX or TDX are
enabled in the BIOS. They will boot with very reduced functionality
without enabling this option.
If you don't know what to do here, say N.
config X86_POSTED_MSI
bool "Enable MSI and MSI-x delivery by posted interrupts"
depends on X86_64 && IRQ_REMAP
help
This enables MSIs that are under interrupt remapping to be delivered as
posted interrupts to the host kernel. Interrupt throughput can
potentially be improved by coalescing CPU notifications during high
frequency bursts.
If you don't know what to do here, say N.
config X86_MPPARSE
bool "Enable MPS table" if ACPI
default y
depends on X86_LOCAL_APIC
help
For old smp systems that do not have proper acpi support. Newer systems
(esp with 64bit cpus) with acpi support, MADT and DSDT will override it
config X86_CPU_RESCTRL
bool "x86 CPU resource control support"
depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
select KERNFS
select PROC_CPU_RESCTRL if PROC_FS
help
Enable x86 CPU resource control support.
Provide support for the allocation and monitoring of system resources
usage by the CPU.
Intel calls this Intel Resource Director Technology
(Intel(R) RDT). More information about RDT can be found in the
Intel x86 Architecture Software Developer Manual.
AMD calls this AMD Platform Quality of Service (AMD QoS).
More information about AMD QoS can be found in the AMD64 Technology
Platform Quality of Service Extensions manual.
Say N if unsure.
config X86_FRED
bool "Flexible Return and Event Delivery"
depends on X86_64
help
When enabled, try to use Flexible Return and Event Delivery
instead of the legacy SYSCALL/SYSENTER/IDT architecture for
ring transitions and exception/interrupt handling if the
system supports it.
config X86_BIGSMP
bool "Support for big SMP systems with more than 8 CPUs"
depends on SMP && X86_32
help
This option is needed for the systems that have more than 8 CPUs.
config X86_EXTENDED_PLATFORM
bool "Support for extended (non-PC) x86 platforms"
default y
help
If you disable this option then the kernel will only support
standard PC platforms. (which covers the vast majority of
systems out there.)
If you enable this option then you'll be able to select support
for the following non-PC x86 platforms, depending on the value of
CONFIG_64BIT.
32-bit platforms (CONFIG_64BIT=n):
Goldfish (Android emulator)
AMD Elan
RDC R-321x SoC
SGI 320/540 (Visual Workstation)
STA2X11-based (e.g. Northville)
Moorestown MID devices
64-bit platforms (CONFIG_64BIT=y):
Numascale NumaChip
ScaleMP vSMP
SGI Ultraviolet
If you have one of these systems, or if you want to build a
generic distribution kernel, say Y here - otherwise say N.
# This is an alphabetically sorted list of 64 bit extended platforms
# Please maintain the alphabetic order if and when there are additions
config X86_NUMACHIP
bool "Numascale NumaChip"
depends on X86_64
depends on X86_EXTENDED_PLATFORM
depends on NUMA
depends on SMP
depends on X86_X2APIC
depends on PCI_MMCONFIG
help
Adds support for Numascale NumaChip large-SMP systems. Needed to
enable more than ~168 cores.
If you don't have one of these, you should say N here.
config X86_VSMP
bool "ScaleMP vSMP"
select HYPERVISOR_GUEST
select PARAVIRT
depends on X86_64 && PCI
depends on X86_EXTENDED_PLATFORM
depends on SMP
help
Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
supposed to run on these EM64T-based machines. Only choose this option
if you have one of these machines.
config X86_UV
bool "SGI Ultraviolet"
depends on X86_64
depends on X86_EXTENDED_PLATFORM
depends on NUMA
depends on EFI
depends on KEXEC_CORE
depends on X86_X2APIC
depends on PCI
help
This option is needed in order to support SGI Ultraviolet systems.
If you don't have one of these, you should say N here.
# Following is an alphabetically sorted list of 32 bit extended platforms
# Please maintain the alphabetic order if and when there are additions
config X86_GOLDFISH
bool "Goldfish (Virtual Platform)"
depends on X86_EXTENDED_PLATFORM
help
Enable support for the Goldfish virtual platform used primarily
for Android development. Unless you are building for the Android
Goldfish emulator say N here.
config X86_INTEL_CE
bool "CE4100 TV platform"
depends on PCI
depends on PCI_GODIRECT
depends on X86_IO_APIC
depends on X86_32
depends on X86_EXTENDED_PLATFORM
select X86_REBOOTFIXUPS
select OF
select OF_EARLY_FLATTREE
help
Select for the Intel CE media processor (CE4100) SOC.
This option compiles in support for the CE4100 SOC for settop
boxes and media devices.
config X86_INTEL_MID
bool "Intel MID platform support"
depends on X86_EXTENDED_PLATFORM
depends on X86_PLATFORM_DEVICES
depends on PCI
depends on X86_64 || (PCI_GOANY && X86_32)
depends on X86_IO_APIC
select I2C
select DW_APB_TIMER
select INTEL_SCU_PCI
help
Select to build a kernel capable of supporting Intel MID (Mobile
Internet Device) platform systems which do not have the PCI legacy
interfaces. If you are building for a PC class system say N here.
Intel MID platforms are based on an Intel processor and chipset which
consume less power than most of the x86 derivatives.
config X86_INTEL_QUARK
bool "Intel Quark platform support"
depends on X86_32
depends on X86_EXTENDED_PLATFORM
depends on X86_PLATFORM_DEVICES
depends on X86_TSC
depends on PCI
depends on PCI_GOANY
depends on X86_IO_APIC
select IOSF_MBI
select INTEL_IMR
select COMMON_CLK
help
Select to include support for Quark X1000 SoC.
Say Y here if you have a Quark based system such as the Arduino
compatible Intel Galileo.
config X86_INTEL_LPSS
bool "Intel Low Power Subsystem Support"
depends on X86 && ACPI && PCI
select COMMON_CLK
select PINCTRL
select IOSF_MBI
help
Select to build support for Intel Low Power Subsystem such as
found on Intel Lynxpoint PCH. Selecting this option enables
things like clock tree (common clock framework) and pincontrol
which are needed by the LPSS peripheral drivers.
config X86_AMD_PLATFORM_DEVICE
bool "AMD ACPI2Platform devices support"
depends on ACPI
select COMMON_CLK
select PINCTRL
help
Select to interpret AMD specific ACPI device to platform device
such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
implemented under PINCTRL subsystem.
config IOSF_MBI
tristate "Intel SoC IOSF Sideband support for SoC platforms"
depends on PCI
help
This option enables sideband register access support for Intel SoC
platforms. On these platforms the IOSF sideband is used in lieu of
MSR's for some register accesses, mostly but not limited to thermal
and power. Drivers may query the availability of this device to
determine if they need the sideband in order to work on these
platforms. The sideband is available on the following SoC products.
This list is not meant to be exclusive.
- BayTrail
- Braswell
- Quark
You should say Y if you are running a kernel on one of these SoC's.
config IOSF_MBI_DEBUG
bool "Enable IOSF sideband access through debugfs"
depends on IOSF_MBI && DEBUG_FS
help
Select this option to expose the IOSF sideband access registers (MCR,
MDR, MCRX) through debugfs to write and read register information from
different units on the SoC. This is most useful for obtaining device
state information for debug and analysis. As this is a general access
mechanism, users of this option would have specific knowledge of the
device they want to access.
If you don't require the option or are in doubt, say N.
config X86_RDC321X
bool "RDC R-321x SoC"
depends on X86_32
depends on X86_EXTENDED_PLATFORM
select M486
select X86_REBOOTFIXUPS
help
This option is needed for RDC R-321x system-on-chip, also known
as R-8610-(G).
If you don't have one of these chips, you should say N here.
config X86_32_NON_STANDARD
bool "Support non-standard 32-bit SMP architectures"
depends on X86_32 && SMP
depends on X86_EXTENDED_PLATFORM
help
This option compiles in the bigsmp and STA2X11 default
subarchitectures. It is intended for a generic binary
kernel. If you select them all, kernel will probe it one by
one and will fallback to default.
# Alphabetically sorted list of Non standard 32 bit platforms
config X86_SUPPORTS_MEMORY_FAILURE
def_bool y
# MCE code calls memory_failure():
depends on X86_MCE
# On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
# On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
depends on X86_64 || !SPARSEMEM
select ARCH_SUPPORTS_MEMORY_FAILURE
config STA2X11
bool "STA2X11 Companion Chip Support"
depends on X86_32_NON_STANDARD && PCI
select SWIOTLB
select MFD_STA2X11
select GPIOLIB
help
This adds support for boards based on the STA2X11 IO-Hub,
a.k.a. "ConneXt". The chip is used in place of the standard
PC chipset, so all "standard" peripherals are missing. If this
option is selected the kernel will still be able to boot on
standard PC machines.
config X86_32_IRIS
tristate "Eurobraille/Iris poweroff module"
depends on X86_32
help
The Iris machines from EuroBraille do not have APM or ACPI support
to shut themselves down properly. A special I/O sequence is
needed to do so, which is what this module does at
kernel shutdown.
This is only for Iris machines from EuroBraille.
If unused, say N.
config SCHED_OMIT_FRAME_POINTER
def_bool y
prompt "Single-depth WCHAN output"
depends on X86
help
Calculate simpler /proc/<PID>/wchan values. If this option
is disabled then wchan values will recurse back to the
caller function. This provides more accurate wchan values,
at the expense of slightly more scheduling overhead.
If in doubt, say "Y".
menuconfig HYPERVISOR_GUEST
bool "Linux guest support"
help
Say Y here to enable options for running Linux under various hyper-
visors. This option enables basic hypervisor detection and platform
setup.
If you say N, all options in this submenu will be skipped and
disabled, and Linux guest support won't be built in.
if HYPERVISOR_GUEST
config PARAVIRT
bool "Enable paravirtualization code"
depends on HAVE_STATIC_CALL
help
This changes the kernel so it can modify itself when it is run
under a hypervisor, potentially improving performance significantly
over full virtualization. However, when run without a hypervisor
the kernel is theoretically slower and slightly larger.
config PARAVIRT_XXL
bool
config PARAVIRT_DEBUG
bool "paravirt-ops debugging"
depends on PARAVIRT && DEBUG_KERNEL
help
Enable to debug paravirt_ops internals. Specifically, BUG if
a paravirt_op is missing when it is called.
config PARAVIRT_SPINLOCKS
bool "Paravirtualization layer for spinlocks"
depends on PARAVIRT && SMP
help
Paravirtualized spinlocks allow a pvops backend to replace the
spinlock implementation with something virtualization-friendly
(for example, block the virtual CPU rather than spinning).
It has a minimal impact on native kernels and gives a nice performance
benefit on paravirtualized KVM / Xen kernels.
If you are unsure how to answer this question, answer Y.
config X86_HV_CALLBACK_VECTOR
def_bool n
source "arch/x86/xen/Kconfig"
config KVM_GUEST
bool "KVM Guest support (including kvmclock)"
depends on PARAVIRT
select PARAVIRT_CLOCK
select ARCH_CPUIDLE_HALTPOLL
select X86_HV_CALLBACK_VECTOR
default y
help
This option enables various optimizations for running under the KVM
hypervisor. It includes a paravirtualized clock, so that instead
of relying on a PIT (or probably other) emulation by the
underlying device model, the host provides the guest with
timing infrastructure such as time of day, and system time
config ARCH_CPUIDLE_HALTPOLL
def_bool n
prompt "Disable host haltpoll when loading haltpoll driver"
help
If virtualized under KVM, disable host haltpoll.
config PVH
bool "Support for running PVH guests"
help
This option enables the PVH entry point for guest virtual machines
as specified in the x86/HVM direct boot ABI.
config PARAVIRT_TIME_ACCOUNTING
bool "Paravirtual steal time accounting"
depends on PARAVIRT
help
Select this option to enable fine granularity task steal time
accounting. Time spent executing other tasks in parallel with
the current vCPU is discounted from the vCPU power. To account for
that, there can be a small performance impact.
If in doubt, say N here.
config PARAVIRT_CLOCK
bool
config JAILHOUSE_GUEST
bool "Jailhouse non-root cell support"
depends on X86_64 && PCI
select X86_PM_TIMER
help
This option allows to run Linux as guest in a Jailhouse non-root
cell. You can leave this option disabled if you only want to start
Jailhouse and run Linux afterwards in the root cell.
config ACRN_GUEST
bool "ACRN Guest support"
depends on X86_64
select X86_HV_CALLBACK_VECTOR
help
This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
a flexible, lightweight reference open-source hypervisor, built with
real-time and safety-criticality in mind. It is built for embedded
IOT with small footprint and real-time features. More details can be
found in https://projectacrn.org/.
config INTEL_TDX_GUEST
bool "Intel TDX (Trust Domain Extensions) - Guest Support"
depends on X86_64 && CPU_SUP_INTEL
depends on X86_X2APIC
depends on EFI_STUB
select ARCH_HAS_CC_PLATFORM
select X86_MEM_ENCRYPT
select X86_MCE
select UNACCEPTED_MEMORY
help
Support running as a guest under Intel TDX. Without this support,
the guest kernel can not boot or run under TDX.
TDX includes memory encryption and integrity capabilities
which protect the confidentiality and integrity of guest
memory contents and CPU state. TDX guests are protected from
some attacks from the VMM.
endif # HYPERVISOR_GUEST
source "arch/x86/Kconfig.cpu"
config HPET_TIMER
def_bool X86_64
prompt "HPET Timer Support" if X86_32
help
Use the IA-PC HPET (High Precision Event Timer) to manage
time in preference to the PIT and RTC, if a HPET is
present.
HPET is the next generation timer replacing legacy 8254s.
The HPET provides a stable time base on SMP
systems, unlike the TSC, but it is more expensive to access,
as it is off-chip. The interface used is documented
in the HPET spec, revision 1.
You can safely choose Y here. However, HPET will only be
activated if the platform and the BIOS support this feature.
Otherwise the 8254 will be used for timing services.
Choose N to continue using the legacy 8254 timer.
config HPET_EMULATE_RTC
def_bool y
depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
# Mark as expert because too many people got it wrong.
# The code disables itself when not needed.
config DMI
default y
select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
bool "Enable DMI scanning" if EXPERT
help
Enabled scanning of DMI to identify machine quirks. Say Y
here unless you have verified that your setup is not
affected by entries in the DMI blacklist. Required by PNP
BIOS code.
config GART_IOMMU
bool "Old AMD GART IOMMU support"
select DMA_OPS
select IOMMU_HELPER
select SWIOTLB
depends on X86_64 && PCI && AMD_NB
help
Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
GART based hardware IOMMUs.
The GART supports full DMA access for devices with 32-bit access
limitations, on systems with more than 3 GB. This is usually needed
for USB, sound, many IDE/SATA chipsets and some other devices.
Newer systems typically have a modern AMD IOMMU, supported via
the CONFIG_AMD_IOMMU=y config option.
In normal configurations this driver is only active when needed:
there's more than 3 GB of memory and the system contains a
32-bit limited device.
If unsure, say Y.
config BOOT_VESA_SUPPORT
bool
help
If true, at least one selected framebuffer driver can take advantage
of VESA video modes set at an early boot stage via the vga= parameter.
config MAXSMP
bool "Enable Maximum number of SMP Processors and NUMA Nodes"
depends on X86_64 && SMP && DEBUG_KERNEL
select CPUMASK_OFFSTACK
help
Enable maximum number of CPUS and NUMA Nodes for this architecture.
If unsure, say N.
#
# The maximum number of CPUs supported:
#
# The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
# and which can be configured interactively in the
# [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
#
# The ranges are different on 32-bit and 64-bit kernels, depending on
# hardware capabilities and scalability features of the kernel.
#
# ( If MAXSMP is enabled we just use the highest possible value and disable
# interactive configuration. )
#
config NR_CPUS_RANGE_BEGIN
int
default NR_CPUS_RANGE_END if MAXSMP
default 1 if !SMP
default 2
config NR_CPUS_RANGE_END
int
depends on X86_32
default 64 if SMP && X86_BIGSMP
default 8 if SMP && !X86_BIGSMP
default 1 if !SMP
config NR_CPUS_RANGE_END
int
depends on X86_64
default 8192 if SMP && CPUMASK_OFFSTACK
default 512 if SMP && !CPUMASK_OFFSTACK
default 1 if !SMP
config NR_CPUS_DEFAULT
int
depends on X86_32
default 32 if X86_BIGSMP
default 8 if SMP
default 1 if !SMP
config NR_CPUS_DEFAULT
int
depends on X86_64
default 8192 if MAXSMP
default 64 if SMP
default 1 if !SMP
config NR_CPUS
int "Maximum number of CPUs" if SMP && !MAXSMP
range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
default NR_CPUS_DEFAULT
help
This allows you to specify the maximum number of CPUs which this
kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
supported value is 8192, otherwise the maximum value is 512. The
minimum value which makes sense is 2.
This is purely to save memory: each supported CPU adds about 8KB
to the kernel image.
config SCHED_CLUSTER
bool "Cluster scheduler support"
depends on SMP
default y
help
Cluster scheduler support improves the CPU scheduler's decision
making when dealing with machines that have clusters of CPUs.
Cluster usually means a couple of CPUs which are placed closely
by sharing mid-level caches, last-level cache tags or internal
busses.
config SCHED_SMT
def_bool y if SMP
config SCHED_MC
def_bool y
prompt "Multi-core scheduler support"
depends on SMP
help
Multi-core scheduler support improves the CPU scheduler's decision
making when dealing with multi-core CPU chips at a cost of slightly
increased overhead in some places. If unsure say N here.
config SCHED_MC_PRIO
bool "CPU core priorities scheduler support"
depends on SCHED_MC
select X86_INTEL_PSTATE if CPU_SUP_INTEL
select X86_AMD_PSTATE if CPU_SUP_AMD && ACPI
select CPU_FREQ
default y
help
Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
core ordering determined at manufacturing time, which allows
certain cores to reach higher turbo frequencies (when running
single threaded workloads) than others.
Enabling this kernel feature teaches the scheduler about
the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
scheduler's CPU selection logic accordingly, so that higher
overall system performance can be achieved.
This feature will have no effect on CPUs without this feature.
If unsure say Y here.
config UP_LATE_INIT
def_bool y
depends on !SMP && X86_LOCAL_APIC
config X86_UP_APIC
bool "Local APIC support on uniprocessors" if !PCI_MSI
default PCI_MSI
depends on X86_32 && !SMP && !X86_32_NON_STANDARD
help
A local APIC (Advanced Programmable Interrupt Controller) is an
integrated interrupt controller in the CPU. If you have a single-CPU
system which has a processor with a local APIC, you can say Y here to
enable and use it. If you say Y here even though your machine doesn't
have a local APIC, then the kernel will still run with no slowdown at
all. The local APIC supports CPU-generated self-interrupts (timer,
performance counters), and the NMI watchdog which detects hard
lockups.
config X86_UP_IOAPIC
bool "IO-APIC support on uniprocessors"
depends on X86_UP_APIC
help
An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
SMP-capable replacement for PC-style interrupt controllers. Most
SMP systems and many recent uniprocessor systems have one.
If you have a single-CPU system with an IO-APIC, you can say Y here
to use it. If you say Y here even though your machine doesn't have
an IO-APIC, then the kernel will still run with no slowdown at all.
config X86_LOCAL_APIC
def_bool y
depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
select IRQ_DOMAIN_HIERARCHY
config X86_IO_APIC
def_bool y
depends on X86_LOCAL_APIC || X86_UP_IOAPIC
config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
bool "Reroute for broken boot IRQs"
depends on X86_IO_APIC
help
This option enables a workaround that fixes a source of
spurious interrupts. This is recommended when threaded
interrupt handling is used on systems where the generation of
superfluous "boot interrupts" cannot be disabled.
Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
entry in the chipset's IO-APIC is masked (as, e.g. the RT
kernel does during interrupt handling). On chipsets where this
boot IRQ generation cannot be disabled, this workaround keeps
the original IRQ line masked so that only the equivalent "boot
IRQ" is delivered to the CPUs. The workaround also tells the
kernel to set up the IRQ handler on the boot IRQ line. In this
way only one interrupt is delivered to the kernel. Otherwise
the spurious second interrupt may cause the kernel to bring
down (vital) interrupt lines.
Only affects "broken" chipsets. Interrupt sharing may be
increased on these systems.
config X86_MCE
bool "Machine Check / overheating reporting"
select GENERIC_ALLOCATOR
default y
help
Machine Check support allows the processor to notify the
kernel if it detects a problem (e.g. overheating, data corruption).
The action the kernel takes depends on the severity of the problem,
ranging from warning messages to halting the machine.
config X86_MCELOG_LEGACY
bool "Support for deprecated /dev/mcelog character device"
depends on X86_MCE
help
Enable support for /dev/mcelog which is needed by the old mcelog
userspace logging daemon. Consider switching to the new generation
rasdaemon solution.
config X86_MCE_INTEL
def_bool y
prompt "Intel MCE features"
depends on X86_MCE && X86_LOCAL_APIC
help
Additional support for intel specific MCE features such as
the thermal monitor.
config X86_MCE_AMD
def_bool y
prompt "AMD MCE features"
depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
help
Additional support for AMD specific MCE features such as
the DRAM Error Threshold.
config X86_ANCIENT_MCE
bool "Support for old Pentium 5 / WinChip machine checks"
depends on X86_32 && X86_MCE
help
Include support for machine check handling on old Pentium 5 or WinChip
systems. These typically need to be enabled explicitly on the command
line.
config X86_MCE_THRESHOLD
depends on X86_MCE_AMD || X86_MCE_INTEL
def_bool y
config X86_MCE_INJECT
depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
tristate "Machine check injector support"
help
Provide support for injecting machine checks for testing purposes.
If you don't know what a machine check is and you don't do kernel
QA it is safe to say n.
source "arch/x86/events/Kconfig"
config X86_LEGACY_VM86
bool "Legacy VM86 support"
depends on X86_32
help
This option allows user programs to put the CPU into V8086
mode, which is an 80286-era approximation of 16-bit real mode.
Some very old versions of X and/or vbetool require this option
for user mode setting. Similarly, DOSEMU will use it if
available to accelerate real mode DOS programs. However, any
recent version of DOSEMU, X, or vbetool should be fully
functional even without kernel VM86 support, as they will all
fall back to software emulation. Nevertheless, if you are using
a 16-bit DOS program where 16-bit performance matters, vm86
mode might be faster than emulation and you might want to
enable this option.
Note that any app that works on a 64-bit kernel is unlikely to
need this option, as 64-bit kernels don't, and can't, support
V8086 mode. This option is also unrelated to 16-bit protected
mode and is not needed to run most 16-bit programs under Wine.
Enabling this option increases the complexity of the kernel
and slows down exception handling a tiny bit.
If unsure, say N here.
config VM86
bool
default X86_LEGACY_VM86
config X86_16BIT
bool "Enable support for 16-bit segments" if EXPERT
default y
depends on MODIFY_LDT_SYSCALL
help
This option is required by programs like Wine to run 16-bit
protected mode legacy code on x86 processors. Disabling
this option saves about 300 bytes on i386, or around 6K text
plus 16K runtime memory on x86-64,
config X86_ESPFIX32
def_bool y
depends on X86_16BIT && X86_32
config X86_ESPFIX64
def_bool y
depends on X86_16BIT && X86_64
config X86_VSYSCALL_EMULATION
bool "Enable vsyscall emulation" if EXPERT
default y
depends on X86_64
help
This enables emulation of the legacy vsyscall page. Disabling
it is roughly equivalent to booting with vsyscall=none, except
that it will also disable the helpful warning if a program
tries to use a vsyscall. With this option set to N, offending
programs will just segfault, citing addresses of the form
0xffffffffff600?00.
This option is required by many programs built before 2013, and
care should be used even with newer programs if set to N.
Disabling this option saves about 7K of kernel size and
possibly 4K of additional runtime pagetable memory.
config X86_IOPL_IOPERM
bool "IOPERM and IOPL Emulation"
default y
help
This enables the ioperm() and iopl() syscalls which are necessary
for legacy applications.
Legacy IOPL support is an overbroad mechanism which allows user
space aside of accessing all 65536 I/O ports also to disable
interrupts. To gain this access the caller needs CAP_SYS_RAWIO
capabilities and permission from potentially active security
modules.
The emulation restricts the functionality of the syscall to
only allowing the full range I/O port access, but prevents the
ability to disable interrupts from user space which would be
granted if the hardware IOPL mechanism would be used.
config TOSHIBA
tristate "Toshiba Laptop support"
depends on X86_32
help
This adds a driver to safely access the System Management Mode of
the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
not work on models with a Phoenix BIOS. The System Management Mode
is used to set the BIOS and power saving options on Toshiba portables.
For information on utilities to make use of this driver see the
Toshiba Linux utilities web site at:
<http://www.buzzard.org.uk/toshiba/>.
Say Y if you intend to run this kernel on a Toshiba portable.
Say N otherwise.
config X86_REBOOTFIXUPS
bool "Enable X86 board specific fixups for reboot"
depends on X86_32
help
This enables chipset and/or board specific fixups to be done
in order to get reboot to work correctly. This is only needed on
some combinations of hardware and BIOS. The symptom, for which
this config is intended, is when reboot ends with a stalled/hung
system.
Currently, the only fixup is for the Geode machines using
CS5530A and CS5536 chipsets and the RDC R-321x SoC.
Say Y if you want to enable the fixup. Currently, it's safe to
enable this option even if you don't need it.
Say N otherwise.
config MICROCODE
def_bool y
depends on CPU_SUP_AMD || CPU_SUP_INTEL
config MICROCODE_INITRD32
def_bool y
depends on MICROCODE && X86_32 && BLK_DEV_INITRD
config MICROCODE_LATE_LOADING
bool "Late microcode loading (DANGEROUS)"
default n
depends on MICROCODE && SMP
help
Loading microcode late, when the system is up and executing instructions
is a tricky business and should be avoided if possible. Just the sequence
of synchronizing all cores and SMT threads is one fragile dance which does
not guarantee that cores might not softlock after the loading. Therefore,
use this at your own risk. Late loading taints the kernel unless the
microcode header indicates that it is safe for late loading via the
minimal revision check. This minimal revision check can be enforced on
the kernel command line with "microcode.minrev=Y".
config MICROCODE_LATE_FORCE_MINREV
bool "Enforce late microcode loading minimal revision check"
default n
depends on MICROCODE_LATE_LOADING
help
To prevent that users load microcode late which modifies already
in use features, newer microcode patches have a minimum revision field
in the microcode header, which tells the kernel which minimum
revision must be active in the CPU to safely load that new microcode
late into the running system. If disabled the check will not
be enforced but the kernel will be tainted when the minimal
revision check fails.
This minimal revision check can also be controlled via the
"microcode.minrev" parameter on the kernel command line.
If unsure say Y.
config X86_MSR
tristate "/dev/cpu/*/msr - Model-specific register support"
help
This device gives privileged processes access to the x86
Model-Specific Registers (MSRs). It is a character device with
major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
MSR accesses are directed to a specific CPU on multi-processor
systems.
config X86_CPUID
tristate "/dev/cpu/*/cpuid - CPU information support"
help
This device gives processes access to the x86 CPUID instruction to
be executed on a specific processor. It is a character device
with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
/dev/cpu/31/cpuid.
choice
prompt "High Memory Support"
default HIGHMEM4G
depends on X86_32
config NOHIGHMEM
bool "off"
help
Linux can use up to 64 Gigabytes of physical memory on x86 systems.
However, the address space of 32-bit x86 processors is only 4
Gigabytes large. That means that, if you have a large amount of
physical memory, not all of it can be "permanently mapped" by the
kernel. The physical memory that's not permanently mapped is called
"high memory".
If you are compiling a kernel which will never run on a machine with
more than 1 Gigabyte total physical RAM, answer "off" here (default
choice and suitable for most users). This will result in a "3GB/1GB"
split: 3GB are mapped so that each process sees a 3GB virtual memory
space and the remaining part of the 4GB virtual memory space is used
by the kernel to permanently map as much physical memory as
possible.
If the machine has between 1 and 4 Gigabytes physical RAM, then
answer "4GB" here.
If more than 4 Gigabytes is used then answer "64GB" here. This
selection turns Intel PAE (Physical Address Extension) mode on.
PAE implements 3-level paging on IA32 processors. PAE is fully
supported by Linux, PAE mode is implemented on all recent Intel
processors (Pentium Pro and better). NOTE: If you say "64GB" here,
then the kernel will not boot on CPUs that don't support PAE!
The actual amount of total physical memory will either be
auto detected or can be forced by using a kernel command line option
such as "mem=256M". (Try "man bootparam" or see the documentation of
your boot loader (lilo or loadlin) about how to pass options to the
kernel at boot time.)
If unsure, say "off".
config HIGHMEM4G
bool "4GB"
help
Select this if you have a 32-bit processor and between 1 and 4
gigabytes of physical RAM.
config HIGHMEM64G
bool "64GB"
depends on X86_HAVE_PAE
select X86_PAE
help
Select this if you have a 32-bit processor and more than 4
gigabytes of physical RAM.
endchoice
choice
prompt "Memory split" if EXPERT
default VMSPLIT_3G
depends on X86_32
help
Select the desired split between kernel and user memory.
If the address range available to the kernel is less than the
physical memory installed, the remaining memory will be available
as "high memory". Accessing high memory is a little more costly
than low memory, as it needs to be mapped into the kernel first.
Note that increasing the kernel address space limits the range
available to user programs, making the address space there
tighter. Selecting anything other than the default 3G/1G split
will also likely make your kernel incompatible with binary-only
kernel modules.
If you are not absolutely sure what you are doing, leave this
option alone!
config VMSPLIT_3G
bool "3G/1G user/kernel split"
config VMSPLIT_3G_OPT
depends on !X86_PAE
bool "3G/1G user/kernel split (for full 1G low memory)"
config VMSPLIT_2G
bool "2G/2G user/kernel split"
config VMSPLIT_2G_OPT
depends on !X86_PAE
bool "2G/2G user/kernel split (for full 2G low memory)"
config VMSPLIT_1G
bool "1G/3G user/kernel split"
endchoice
config PAGE_OFFSET
hex
default 0xB0000000 if VMSPLIT_3G_OPT
default 0x80000000 if VMSPLIT_2G
default 0x78000000 if VMSPLIT_2G_OPT
default 0x40000000 if VMSPLIT_1G
default 0xC0000000
depends on X86_32
config HIGHMEM
def_bool y
depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
config X86_PAE
bool "PAE (Physical Address Extension) Support"
depends on X86_32 && X86_HAVE_PAE
select PHYS_ADDR_T_64BIT
select SWIOTLB
help
PAE is required for NX support, and furthermore enables
larger swapspace support for non-overcommit purposes. It
has the cost of more pagetable lookup overhead, and also
consumes more pagetable space per process.
config X86_5LEVEL
bool "Enable 5-level page tables support"
default y
select DYNAMIC_MEMORY_LAYOUT
select SPARSEMEM_VMEMMAP
depends on X86_64
help
5-level paging enables access to larger address space:
up to 128 PiB of virtual address space and 4 PiB of
physical address space.
It will be supported by future Intel CPUs.
A kernel with the option enabled can be booted on machines that
support 4- or 5-level paging.
See Documentation/arch/x86/x86_64/5level-paging.rst for more
information.
Say N if unsure.
config X86_DIRECT_GBPAGES
def_bool y
depends on X86_64
help
Certain kernel features effectively disable kernel
linear 1 GB mappings (even if the CPU otherwise
supports them), so don't confuse the user by printing
that we have them enabled.
config X86_CPA_STATISTICS
bool "Enable statistic for Change Page Attribute"
depends on DEBUG_FS
help
Expose statistics about the Change Page Attribute mechanism, which
helps to determine the effectiveness of preserving large and huge
page mappings when mapping protections are changed.
config X86_MEM_ENCRYPT
select ARCH_HAS_FORCE_DMA_UNENCRYPTED
select DYNAMIC_PHYSICAL_MASK
def_bool n
config AMD_MEM_ENCRYPT
bool "AMD Secure Memory Encryption (SME) support"
depends on X86_64 && CPU_SUP_AMD
depends on EFI_STUB
select DMA_COHERENT_POOL
select ARCH_USE_MEMREMAP_PROT
select INSTRUCTION_DECODER
select ARCH_HAS_CC_PLATFORM
select X86_MEM_ENCRYPT
select UNACCEPTED_MEMORY
help
Say yes to enable support for the encryption of system memory.
This requires an AMD processor that supports Secure Memory
Encryption (SME).
# Common NUMA Features
config NUMA
bool "NUMA Memory Allocation and Scheduler Support"
depends on SMP
depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
default y if X86_BIGSMP
select USE_PERCPU_NUMA_NODE_ID
select OF_NUMA if OF
help
Enable NUMA (Non-Uniform Memory Access) support.
The kernel will try to allocate memory used by a CPU on the
local memory controller of the CPU and add some more
NUMA awareness to the kernel.
For 64-bit this is recommended if the system is Intel Core i7
(or later), AMD Opteron, or EM64T NUMA.
For 32-bit this is only needed if you boot a 32-bit
kernel on a 64-bit NUMA platform.
Otherwise, you should say N.
config AMD_NUMA
def_bool y
prompt "Old style AMD Opteron NUMA detection"
depends on X86_64 && NUMA && PCI
help
Enable AMD NUMA node topology detection. You should say Y here if
you have a multi processor AMD system. This uses an old method to
read the NUMA configuration directly from the builtin Northbridge
of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
which also takes priority if both are compiled in.
config X86_64_ACPI_NUMA
def_bool y
prompt "ACPI NUMA detection"
depends on X86_64 && NUMA && ACPI && PCI
select ACPI_NUMA
help
Enable ACPI SRAT based node topology detection.
config NUMA_EMU
bool "NUMA emulation"
depends on NUMA
help
Enable NUMA emulation. A flat machine will be split
into virtual nodes when booted with "numa=fake=N", where N is the
number of nodes. This is only useful for debugging.
config NODES_SHIFT
int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
range 1 10
default "10" if MAXSMP
default "6" if X86_64
default "3"
depends on NUMA
help
Specify the maximum number of NUMA Nodes available on the target
system. Increases memory reserved to accommodate various tables.
config ARCH_FLATMEM_ENABLE
def_bool y
depends on X86_32 && !NUMA
config ARCH_SPARSEMEM_ENABLE
def_bool y
depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
select SPARSEMEM_STATIC if X86_32
select SPARSEMEM_VMEMMAP_ENABLE if X86_64
config ARCH_SPARSEMEM_DEFAULT
def_bool X86_64 || (NUMA && X86_32)
config ARCH_SELECT_MEMORY_MODEL
def_bool y
depends on ARCH_SPARSEMEM_ENABLE && ARCH_FLATMEM_ENABLE
config ARCH_MEMORY_PROBE
bool "Enable sysfs memory/probe interface"
depends on MEMORY_HOTPLUG
help
This option enables a sysfs memory/probe interface for testing.
See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
If you are unsure how to answer this question, answer N.
config ARCH_PROC_KCORE_TEXT
def_bool y
depends on X86_64 && PROC_KCORE
config ILLEGAL_POINTER_VALUE
hex
default 0 if X86_32
default 0xdead000000000000 if X86_64
config X86_PMEM_LEGACY_DEVICE
bool
config X86_PMEM_LEGACY
tristate "Support non-standard NVDIMMs and ADR protected memory"
depends on PHYS_ADDR_T_64BIT
depends on BLK_DEV
select X86_PMEM_LEGACY_DEVICE
select NUMA_KEEP_MEMINFO if NUMA
select LIBNVDIMM
help
Treat memory marked using the non-standard e820 type of 12 as used
by the Intel Sandy Bridge-EP reference BIOS as protected memory.
The kernel will offer these regions to the 'pmem' driver so
they can be used for persistent storage.
Say Y if unsure.
config HIGHPTE
bool "Allocate 3rd-level pagetables from highmem"
depends on HIGHMEM
help
The VM uses one page table entry for each page of physical memory.
For systems with a lot of RAM, this can be wasteful of precious
low memory. Setting this option will put user-space page table
entries in high memory.
config X86_CHECK_BIOS_CORRUPTION
bool "Check for low memory corruption"
help
Periodically check for memory corruption in low memory, which
is suspected to be caused by BIOS. Even when enabled in the
configuration, it is disabled at runtime. Enable it by
setting "memory_corruption_check=1" on the kernel command
line. By default it scans the low 64k of memory every 60
seconds; see the memory_corruption_check_size and
memory_corruption_check_period parameters in
Documentation/admin-guide/kernel-parameters.rst to adjust this.
When enabled with the default parameters, this option has
almost no overhead, as it reserves a relatively small amount
of memory and scans it infrequently. It both detects corruption
and prevents it from affecting the running system.
It is, however, intended as a diagnostic tool; if repeatable
BIOS-originated corruption always affects the same memory,
you can use memmap= to prevent the kernel from using that
memory.
config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
bool "Set the default setting of memory_corruption_check"
depends on X86_CHECK_BIOS_CORRUPTION
default y
help
Set whether the default state of memory_corruption_check is
on or off.
config MATH_EMULATION
bool
depends on MODIFY_LDT_SYSCALL
prompt "Math emulation" if X86_32 && (M486SX || MELAN)
help
Linux can emulate a math coprocessor (used for floating point
operations) if you don't have one. 486DX and Pentium processors have
a math coprocessor built in, 486SX and 386 do not, unless you added
a 487DX or 387, respectively. (The messages during boot time can
give you some hints here ["man dmesg"].) Everyone needs either a
coprocessor or this emulation.
If you don't have a math coprocessor, you need to say Y here; if you
say Y here even though you have a coprocessor, the coprocessor will
be used nevertheless. (This behavior can be changed with the kernel
command line option "no387", which comes handy if your coprocessor
is broken. Try "man bootparam" or see the documentation of your boot
loader (lilo or loadlin) about how to pass options to the kernel at
boot time.) This means that it is a good idea to say Y here if you
intend to use this kernel on different machines.
More information about the internals of the Linux math coprocessor
emulation can be found in <file:arch/x86/math-emu/README>.
If you are not sure, say Y; apart from resulting in a 66 KB bigger
kernel, it won't hurt.
config MTRR
def_bool y
prompt "MTRR (Memory Type Range Register) support" if EXPERT
help
On Intel P6 family processors (Pentium Pro, Pentium II and later)
the Memory Type Range Registers (MTRRs) may be used to control
processor access to memory ranges. This is most useful if you have
a video (VGA) card on a PCI or AGP bus. Enabling write-combining
allows bus write transfers to be combined into a larger transfer
before bursting over the PCI/AGP bus. This can increase performance
of image write operations 2.5 times or more. Saying Y here creates a
/proc/mtrr file which may be used to manipulate your processor's
MTRRs. Typically the X server should use this.
This code has a reasonably generic interface so that similar
control registers on other processors can be easily supported
as well:
The Cyrix 6x86, 6x86MX and M II processors have Address Range
Registers (ARRs) which provide a similar functionality to MTRRs. For
these, the ARRs are used to emulate the MTRRs.
The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
write-combining. All of these processors are supported by this code
and it makes sense to say Y here if you have one of them.
Saying Y here also fixes a problem with buggy SMP BIOSes which only
set the MTRRs for the boot CPU and not for the secondary CPUs. This
can lead to all sorts of problems, so it's good to say Y here.
You can safely say Y even if your machine doesn't have MTRRs, you'll
just add about 9 KB to your kernel.
See <file:Documentation/arch/x86/mtrr.rst> for more information.
config MTRR_SANITIZER
def_bool y
prompt "MTRR cleanup support"
depends on MTRR
help
Convert MTRR layout from continuous to discrete, so X drivers can
add writeback entries.
Can be disabled with disable_mtrr_cleanup on the kernel command line.
The largest mtrr entry size for a continuous block can be set with
mtrr_chunk_size.
If unsure, say Y.
config MTRR_SANITIZER_ENABLE_DEFAULT
int "MTRR cleanup enable value (0-1)"
range 0 1
default "0"
depends on MTRR_SANITIZER
help
Enable mtrr cleanup default value
config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
int "MTRR cleanup spare reg num (0-7)"
range 0 7
default "1"
depends on MTRR_SANITIZER
help
mtrr cleanup spare entries default, it can be changed via
mtrr_spare_reg_nr=N on the kernel command line.
config X86_PAT
def_bool y
prompt "x86 PAT support" if EXPERT
depends on MTRR
help
Use PAT attributes to setup page level cache control.
PATs are the modern equivalents of MTRRs and are much more
flexible than MTRRs.
Say N here if you see bootup problems (boot crash, boot hang,
spontaneous reboots) or a non-working video driver.
If unsure, say Y.
config ARCH_USES_PG_UNCACHED
def_bool y
depends on X86_PAT
config X86_UMIP
def_bool y
prompt "User Mode Instruction Prevention" if EXPERT
help
User Mode Instruction Prevention (UMIP) is a security feature in
some x86 processors. If enabled, a general protection fault is
issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
executed in user mode. These instructions unnecessarily expose
information about the hardware state.
The vast majority of applications do not use these instructions.
For the very few that do, software emulation is provided in
specific cases in protected and virtual-8086 modes. Emulated
results are dummy.
config CC_HAS_IBT
# GCC >= 9 and binutils >= 2.29
# Retpoline check to work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93654
# Clang/LLVM >= 14
# https://github.com/llvm/llvm-project/commit/e0b89df2e0f0130881bf6c39bf31d7f6aac00e0f
# https://github.com/llvm/llvm-project/commit/dfcf69770bc522b9e411c66454934a37c1f35332
def_bool ((CC_IS_GCC && $(cc-option, -fcf-protection=branch -mindirect-branch-register)) || \
(CC_IS_CLANG && CLANG_VERSION >= 140000)) && \
$(as-instr,endbr64)
config X86_CET
def_bool n
help
CET features configured (Shadow stack or IBT)
config X86_KERNEL_IBT
prompt "Indirect Branch Tracking"
def_bool y
depends on X86_64 && CC_HAS_IBT && HAVE_OBJTOOL
# https://github.com/llvm/llvm-project/commit/9d7001eba9c4cb311e03cd8cdc231f9e579f2d0f
depends on !LD_IS_LLD || LLD_VERSION >= 140000
select OBJTOOL
select X86_CET
help
Build the kernel with support for Indirect Branch Tracking, a
hardware support course-grain forward-edge Control Flow Integrity
protection. It enforces that all indirect calls must land on
an ENDBR instruction, as such, the compiler will instrument the
code with them to make this happen.
In addition to building the kernel with IBT, seal all functions that
are not indirect call targets, avoiding them ever becoming one.
This requires LTO like objtool runs and will slow down the build. It
does significantly reduce the number of ENDBR instructions in the
kernel image.
config X86_INTEL_MEMORY_PROTECTION_KEYS
prompt "Memory Protection Keys"
def_bool y
# Note: only available in 64-bit mode
depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
select ARCH_USES_HIGH_VMA_FLAGS
select ARCH_HAS_PKEYS
help
Memory Protection Keys provides a mechanism for enforcing
page-based protections, but without requiring modification of the
page tables when an application changes protection domains.
For details, see Documentation/core-api/protection-keys.rst
If unsure, say y.
choice
prompt "TSX enable mode"
depends on CPU_SUP_INTEL
default X86_INTEL_TSX_MODE_OFF
help
Intel's TSX (Transactional Synchronization Extensions) feature
allows to optimize locking protocols through lock elision which
can lead to a noticeable performance boost.
On the other hand it has been shown that TSX can be exploited
to form side channel attacks (e.g. TAA) and chances are there
will be more of those attacks discovered in the future.
Therefore TSX is not enabled by default (aka tsx=off). An admin
might override this decision by tsx=on the command line parameter.
Even with TSX enabled, the kernel will attempt to enable the best
possible TAA mitigation setting depending on the microcode available
for the particular machine.
This option allows to set the default tsx mode between tsx=on, =off
and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
details.
Say off if not sure, auto if TSX is in use but it should be used on safe
platforms or on if TSX is in use and the security aspect of tsx is not
relevant.
config X86_INTEL_TSX_MODE_OFF
bool "off"
help
TSX is disabled if possible - equals to tsx=off command line parameter.
config X86_INTEL_TSX_MODE_ON
bool "on"
help
TSX is always enabled on TSX capable HW - equals the tsx=on command
line parameter.
config X86_INTEL_TSX_MODE_AUTO
bool "auto"
help
TSX is enabled on TSX capable HW that is believed to be safe against
side channel attacks- equals the tsx=auto command line parameter.
endchoice
config X86_SGX
bool "Software Guard eXtensions (SGX)"
depends on X86_64 && CPU_SUP_INTEL && X86_X2APIC
depends on CRYPTO=y
depends on CRYPTO_SHA256=y
select MMU_NOTIFIER
select NUMA_KEEP_MEMINFO if NUMA
select XARRAY_MULTI
help
Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
that can be used by applications to set aside private regions of code
and data, referred to as enclaves. An enclave's private memory can
only be accessed by code running within the enclave. Accesses from
outside the enclave, including other enclaves, are disallowed by
hardware.
If unsure, say N.
config X86_USER_SHADOW_STACK
bool "X86 userspace shadow stack"
depends on AS_WRUSS
depends on X86_64
select ARCH_USES_HIGH_VMA_FLAGS
select X86_CET
help
Shadow stack protection is a hardware feature that detects function
return address corruption. This helps mitigate ROP attacks.
Applications must be enabled to use it, and old userspace does not
get protection "for free".
CPUs supporting shadow stacks were first released in 2020.
See Documentation/arch/x86/shstk.rst for more information.
If unsure, say N.
config INTEL_TDX_HOST
bool "Intel Trust Domain Extensions (TDX) host support"
depends on CPU_SUP_INTEL
depends on X86_64
depends on KVM_INTEL
depends on X86_X2APIC
select ARCH_KEEP_MEMBLOCK
depends on CONTIG_ALLOC
depends on !KEXEC_CORE
depends on X86_MCE
help
Intel Trust Domain Extensions (TDX) protects guest VMs from malicious
host and certain physical attacks. This option enables necessary TDX
support in the host kernel to run confidential VMs.
If unsure, say N.
config EFI
bool "EFI runtime service support"
depends on ACPI
select UCS2_STRING
select EFI_RUNTIME_WRAPPERS
select ARCH_USE_MEMREMAP_PROT
select EFI_RUNTIME_MAP if KEXEC_CORE
help
This enables the kernel to use EFI runtime services that are
available (such as the EFI variable services).
This option is only useful on systems that have EFI firmware.
In addition, you should use the latest ELILO loader available
at <http://elilo.sourceforge.net> in order to take advantage
of EFI runtime services. However, even with this option, the
resultant kernel should continue to boot on existing non-EFI
platforms.
config EFI_STUB
bool "EFI stub support"
depends on EFI
select RELOCATABLE
help
This kernel feature allows a bzImage to be loaded directly
by EFI firmware without the use of a bootloader.
See Documentation/admin-guide/efi-stub.rst for more information.
config EFI_HANDOVER_PROTOCOL
bool "EFI handover protocol (DEPRECATED)"
depends on EFI_STUB
default y
help
Select this in order to include support for the deprecated EFI
handover protocol, which defines alternative entry points into the
EFI stub. This is a practice that has no basis in the UEFI
specification, and requires a priori knowledge on the part of the
bootloader about Linux/x86 specific ways of passing the command line
and initrd, and where in memory those assets may be loaded.
If in doubt, say Y. Even though the corresponding support is not
present in upstream GRUB or other bootloaders, most distros build
GRUB with numerous downstream patches applied, and may rely on the
handover protocol as as result.
config EFI_MIXED
bool "EFI mixed-mode support"
depends on EFI_STUB && X86_64
help
Enabling this feature allows a 64-bit kernel to be booted
on a 32-bit firmware, provided that your CPU supports 64-bit
mode.
Note that it is not possible to boot a mixed-mode enabled
kernel via the EFI boot stub - a bootloader that supports
the EFI handover protocol must be used.
If unsure, say N.
config EFI_FAKE_MEMMAP
bool "Enable EFI fake memory map"
depends on EFI
help
Saying Y here will enable "efi_fake_mem" boot option. By specifying
this parameter, you can add arbitrary attribute to specific memory
range by updating original (firmware provided) EFI memmap. This is
useful for debugging of EFI memmap related feature, e.g., Address
Range Mirroring feature.
config EFI_MAX_FAKE_MEM
int "maximum allowable number of ranges in efi_fake_mem boot option"
depends on EFI_FAKE_MEMMAP
range 1 128
default 8
help
Maximum allowable number of ranges in efi_fake_mem boot option.
Ranges can be set up to this value using comma-separated list.
The default value is 8.
config EFI_RUNTIME_MAP
bool "Export EFI runtime maps to sysfs" if EXPERT
depends on EFI
help
Export EFI runtime memory regions to /sys/firmware/efi/runtime-map.
That memory map is required by the 2nd kernel to set up EFI virtual
mappings after kexec, but can also be used for debugging purposes.
See also Documentation/ABI/testing/sysfs-firmware-efi-runtime-map.
source "kernel/Kconfig.hz"
config ARCH_SUPPORTS_KEXEC
def_bool y
config ARCH_SUPPORTS_KEXEC_FILE
def_bool X86_64
config ARCH_SELECTS_KEXEC_FILE
def_bool y
depends on KEXEC_FILE
select HAVE_IMA_KEXEC if IMA
config ARCH_SUPPORTS_KEXEC_PURGATORY
def_bool y
config ARCH_SUPPORTS_KEXEC_SIG
def_bool y
config ARCH_SUPPORTS_KEXEC_SIG_FORCE
def_bool y
config ARCH_SUPPORTS_KEXEC_BZIMAGE_VERIFY_SIG
def_bool y
config ARCH_SUPPORTS_KEXEC_JUMP
def_bool y
config ARCH_SUPPORTS_CRASH_DUMP
def_bool X86_64 || (X86_32 && HIGHMEM)
config ARCH_SUPPORTS_CRASH_HOTPLUG
def_bool y
config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
def_bool CRASH_RESERVE
config PHYSICAL_START
hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
default "0x1000000"
help
This gives the physical address where the kernel is loaded.
If the kernel is not relocatable (CONFIG_RELOCATABLE=n) then bzImage
will decompress itself to above physical address and run from there.
Otherwise, bzImage will run from the address where it has been loaded
by the boot loader. The only exception is if it is loaded below the
above physical address, in which case it will relocate itself there.
In normal kdump cases one does not have to set/change this option
as now bzImage can be compiled as a completely relocatable image
(CONFIG_RELOCATABLE=y) and be used to load and run from a different
address. This option is mainly useful for the folks who don't want
to use a bzImage for capturing the crash dump and want to use a
vmlinux instead. vmlinux is not relocatable hence a kernel needs
to be specifically compiled to run from a specific memory area
(normally a reserved region) and this option comes handy.
So if you are using bzImage for capturing the crash dump,
leave the value here unchanged to 0x1000000 and set
CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
for capturing the crash dump change this value to start of
the reserved region. In other words, it can be set based on
the "X" value as specified in the "crashkernel=YM@XM"
command line boot parameter passed to the panic-ed
kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
for more details about crash dumps.
Usage of bzImage for capturing the crash dump is recommended as
one does not have to build two kernels. Same kernel can be used
as production kernel and capture kernel. Above option should have
gone away after relocatable bzImage support is introduced. But it
is present because there are users out there who continue to use
vmlinux for dump capture. This option should go away down the
line.
Don't change this unless you know what you are doing.
config RELOCATABLE
bool "Build a relocatable kernel"
default y
help
This builds a kernel image that retains relocation information
so it can be loaded someplace besides the default 1MB.
The relocations tend to make the kernel binary about 10% larger,
but are discarded at runtime.
One use is for the kexec on panic case where the recovery kernel
must live at a different physical address than the primary
kernel.
Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
it has been loaded at and the compile time physical address
(CONFIG_PHYSICAL_START) is used as the minimum location.
config RANDOMIZE_BASE
bool "Randomize the address of the kernel image (KASLR)"
depends on RELOCATABLE
default y
help
In support of Kernel Address Space Layout Randomization (KASLR),
this randomizes the physical address at which the kernel image
is decompressed and the virtual address where the kernel
image is mapped, as a security feature that deters exploit
attempts relying on knowledge of the location of kernel
code internals.
On 64-bit, the kernel physical and virtual addresses are
randomized separately. The physical address will be anywhere
between 16MB and the top of physical memory (up to 64TB). The
virtual address will be randomized from 16MB up to 1GB (9 bits
of entropy). Note that this also reduces the memory space
available to kernel modules from 1.5GB to 1GB.
On 32-bit, the kernel physical and virtual addresses are
randomized together. They will be randomized from 16MB up to
512MB (8 bits of entropy).
Entropy is generated using the RDRAND instruction if it is
supported. If RDTSC is supported, its value is mixed into
the entropy pool as well. If neither RDRAND nor RDTSC are
supported, then entropy is read from the i8254 timer. The
usable entropy is limited by the kernel being built using
2GB addressing, and that PHYSICAL_ALIGN must be at a
minimum of 2MB. As a result, only 10 bits of entropy are
theoretically possible, but the implementations are further
limited due to memory layouts.
If unsure, say Y.
# Relocation on x86 needs some additional build support
config X86_NEED_RELOCS
def_bool y
depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
config PHYSICAL_ALIGN
hex "Alignment value to which kernel should be aligned"
default "0x200000"
range 0x2000 0x1000000 if X86_32
range 0x200000 0x1000000 if X86_64
help
This value puts the alignment restrictions on physical address
where kernel is loaded and run from. Kernel is compiled for an
address which meets above alignment restriction.
If bootloader loads the kernel at a non-aligned address and
CONFIG_RELOCATABLE is set, kernel will move itself to nearest
address aligned to above value and run from there.
If bootloader loads the kernel at a non-aligned address and
CONFIG_RELOCATABLE is not set, kernel will ignore the run time
load address and decompress itself to the address it has been
compiled for and run from there. The address for which kernel is
compiled already meets above alignment restrictions. Hence the
end result is that kernel runs from a physical address meeting
above alignment restrictions.
On 32-bit this value must be a multiple of 0x2000. On 64-bit
this value must be a multiple of 0x200000.
Don't change this unless you know what you are doing.
config DYNAMIC_MEMORY_LAYOUT
bool
help
This option makes base addresses of vmalloc and vmemmap as well as
__PAGE_OFFSET movable during boot.
config RANDOMIZE_MEMORY
bool "Randomize the kernel memory sections"
depends on X86_64
depends on RANDOMIZE_BASE
select DYNAMIC_MEMORY_LAYOUT
default RANDOMIZE_BASE
help
Randomizes the base virtual address of kernel memory sections
(physical memory mapping, vmalloc & vmemmap). This security feature
makes exploits relying on predictable memory locations less reliable.
The order of allocations remains unchanged. Entropy is generated in
the same way as RANDOMIZE_BASE. Current implementation in the optimal
configuration have in average 30,000 different possible virtual
addresses for each memory section.
If unsure, say Y.
config RANDOMIZE_MEMORY_PHYSICAL_PADDING
hex "Physical memory mapping padding" if EXPERT
depends on RANDOMIZE_MEMORY
default "0xa" if MEMORY_HOTPLUG
default "0x0"
range 0x1 0x40 if MEMORY_HOTPLUG
range 0x0 0x40
help
Define the padding in terabytes added to the existing physical
memory size during kernel memory randomization. It is useful
for memory hotplug support but reduces the entropy available for
address randomization.
If unsure, leave at the default value.
config ADDRESS_MASKING
bool "Linear Address Masking support"
depends on X86_64
help
Linear Address Masking (LAM) modifies the checking that is applied
to 64-bit linear addresses, allowing software to use of the
untranslated address bits for metadata.
The capability can be used for efficient address sanitizers (ASAN)
implementation and for optimizations in JITs.
config HOTPLUG_CPU
def_bool y
depends on SMP
config COMPAT_VDSO
def_bool n
prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
depends on COMPAT_32
help
Certain buggy versions of glibc will crash if they are
presented with a 32-bit vDSO that is not mapped at the address
indicated in its segment table.
The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
the only released version with the bug, but OpenSUSE 9
contains a buggy "glibc 2.3.2".
The symptom of the bug is that everything crashes on startup, saying:
dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Saying Y here changes the default value of the vdso32 boot
option from 1 to 0, which turns off the 32-bit vDSO entirely.
This works around the glibc bug but hurts performance.
If unsure, say N: if you are compiling your own kernel, you
are unlikely to be using a buggy version of glibc.
choice
prompt "vsyscall table for legacy applications"
depends on X86_64
default LEGACY_VSYSCALL_XONLY
help
Legacy user code that does not know how to find the vDSO expects
to be able to issue three syscalls by calling fixed addresses in
kernel space. Since this location is not randomized with ASLR,
it can be used to assist security vulnerability exploitation.
This setting can be changed at boot time via the kernel command
line parameter vsyscall=[emulate|xonly|none]. Emulate mode
is deprecated and can only be enabled using the kernel command
line.
On a system with recent enough glibc (2.14 or newer) and no
static binaries, you can say None without a performance penalty
to improve security.
If unsure, select "Emulate execution only".
config LEGACY_VSYSCALL_XONLY
bool "Emulate execution only"
help
The kernel traps and emulates calls into the fixed vsyscall
address mapping and does not allow reads. This
configuration is recommended when userspace might use the
legacy vsyscall area but support for legacy binary
instrumentation of legacy code is not needed. It mitigates
certain uses of the vsyscall area as an ASLR-bypassing
buffer.
config LEGACY_VSYSCALL_NONE
bool "None"
help
There will be no vsyscall mapping at all. This will
eliminate any risk of ASLR bypass due to the vsyscall
fixed address mapping. Attempts to use the vsyscalls
will be reported to dmesg, so that either old or
malicious userspace programs can be identified.
endchoice
config CMDLINE_BOOL
bool "Built-in kernel command line"
help
Allow for specifying boot arguments to the kernel at
build time. On some systems (e.g. embedded ones), it is
necessary or convenient to provide some or all of the
kernel boot arguments with the kernel itself (that is,
to not rely on the boot loader to provide them.)
To compile command line arguments into the kernel,
set this option to 'Y', then fill in the
boot arguments in CONFIG_CMDLINE.
Systems with fully functional boot loaders (i.e. non-embedded)
should leave this option set to 'N'.
config CMDLINE
string "Built-in kernel command string"
depends on CMDLINE_BOOL
default ""
help
Enter arguments here that should be compiled into the kernel
image and used at boot time. If the boot loader provides a
command line at boot time, it is appended to this string to
form the full kernel command line, when the system boots.
However, you can use the CONFIG_CMDLINE_OVERRIDE option to
change this behavior.
In most cases, the command line (whether built-in or provided
by the boot loader) should specify the device for the root
file system.
config CMDLINE_OVERRIDE
bool "Built-in command line overrides boot loader arguments"
depends on CMDLINE_BOOL && CMDLINE != ""
help
Set this option to 'Y' to have the kernel ignore the boot loader
command line, and use ONLY the built-in command line.
This is used to work around broken boot loaders. This should
be set to 'N' under normal conditions.
config MODIFY_LDT_SYSCALL
bool "Enable the LDT (local descriptor table)" if EXPERT
default y
help
Linux can allow user programs to install a per-process x86
Local Descriptor Table (LDT) using the modify_ldt(2) system
call. This is required to run 16-bit or segmented code such as
DOSEMU or some Wine programs. It is also used by some very old
threading libraries.
Enabling this feature adds a small amount of overhead to
context switches and increases the low-level kernel attack
surface. Disabling it removes the modify_ldt(2) system call.
Saying 'N' here may make sense for embedded or server kernels.
config STRICT_SIGALTSTACK_SIZE
bool "Enforce strict size checking for sigaltstack"
depends on DYNAMIC_SIGFRAME
help
For historical reasons MINSIGSTKSZ is a constant which became
already too small with AVX512 support. Add a mechanism to
enforce strict checking of the sigaltstack size against the
real size of the FPU frame. This option enables the check
by default. It can also be controlled via the kernel command
line option 'strict_sas_size' independent of this config
switch. Enabling it might break existing applications which
allocate a too small sigaltstack but 'work' because they
never get a signal delivered.
Say 'N' unless you want to really enforce this check.
config CFI_AUTO_DEFAULT
bool "Attempt to use FineIBT by default at boot time"
depends on FINEIBT
default y
help
Attempt to use FineIBT by default at boot time. If enabled,
this is the same as booting with "cfi=auto". If disabled,
this is the same as booting with "cfi=kcfi".
source "kernel/livepatch/Kconfig"
endmenu
config CC_HAS_NAMED_AS
def_bool CC_IS_GCC && GCC_VERSION >= 90100
config CC_HAS_NAMED_AS_FIXED_SANITIZERS
def_bool CC_IS_GCC && GCC_VERSION >= 130300
config USE_X86_SEG_SUPPORT
def_bool y
depends on CC_HAS_NAMED_AS
#
# -fsanitize=kernel-address (KASAN) and -fsanitize=thread
# (KCSAN) are incompatible with named address spaces with
# GCC < 13.3 - see GCC PR sanitizer/111736.
#
depends on !(KASAN || KCSAN) || CC_HAS_NAMED_AS_FIXED_SANITIZERS
config CC_HAS_SLS
def_bool $(cc-option,-mharden-sls=all)
config CC_HAS_RETURN_THUNK
def_bool $(cc-option,-mfunction-return=thunk-extern)
config CC_HAS_ENTRY_PADDING
def_bool $(cc-option,-fpatchable-function-entry=16,16)
config FUNCTION_PADDING_CFI
int
default 59 if FUNCTION_ALIGNMENT_64B
default 27 if FUNCTION_ALIGNMENT_32B
default 11 if FUNCTION_ALIGNMENT_16B
default 3 if FUNCTION_ALIGNMENT_8B
default 0
# Basically: FUNCTION_ALIGNMENT - 5*CFI_CLANG
# except Kconfig can't do arithmetic :/
config FUNCTION_PADDING_BYTES
int
default FUNCTION_PADDING_CFI if CFI_CLANG
default FUNCTION_ALIGNMENT
config CALL_PADDING
def_bool n
depends on CC_HAS_ENTRY_PADDING && OBJTOOL
select FUNCTION_ALIGNMENT_16B
config FINEIBT
def_bool y
depends on X86_KERNEL_IBT && CFI_CLANG && MITIGATION_RETPOLINE
select CALL_PADDING
config HAVE_CALL_THUNKS
def_bool y
depends on CC_HAS_ENTRY_PADDING && MITIGATION_RETHUNK && OBJTOOL
config CALL_THUNKS
def_bool n
select CALL_PADDING
config PREFIX_SYMBOLS
def_bool y
depends on CALL_PADDING && !CFI_CLANG
menuconfig CPU_MITIGATIONS
bool "Mitigations for CPU vulnerabilities"
default y
help
Say Y here to enable options which enable mitigations for hardware
vulnerabilities (usually related to speculative execution).
Mitigations can be disabled or restricted to SMT systems at runtime
via the "mitigations" kernel parameter.
If you say N, all mitigations will be disabled. This CANNOT be
overridden at runtime.
Say 'Y', unless you really know what you are doing.
if CPU_MITIGATIONS
config MITIGATION_PAGE_TABLE_ISOLATION
bool "Remove the kernel mapping in user mode"
default y
depends on (X86_64 || X86_PAE)
help
This feature reduces the number of hardware side channels by
ensuring that the majority of kernel addresses are not mapped
into userspace.
See Documentation/arch/x86/pti.rst for more details.
config MITIGATION_RETPOLINE
bool "Avoid speculative indirect branches in kernel"
select OBJTOOL if HAVE_OBJTOOL
default y
help
Compile kernel with the retpoline compiler options to guard against
kernel-to-user data leaks by avoiding speculative indirect
branches. Requires a compiler with -mindirect-branch=thunk-extern
support for full protection. The kernel may run slower.
config MITIGATION_RETHUNK
bool "Enable return-thunks"
depends on MITIGATION_RETPOLINE && CC_HAS_RETURN_THUNK
select OBJTOOL if HAVE_OBJTOOL
default y if X86_64
help
Compile the kernel with the return-thunks compiler option to guard
against kernel-to-user data leaks by avoiding return speculation.
Requires a compiler with -mfunction-return=thunk-extern
support for full protection. The kernel may run slower.
config MITIGATION_UNRET_ENTRY
bool "Enable UNRET on kernel entry"
depends on CPU_SUP_AMD && MITIGATION_RETHUNK && X86_64
default y
help
Compile the kernel with support for the retbleed=unret mitigation.
config MITIGATION_CALL_DEPTH_TRACKING
bool "Mitigate RSB underflow with call depth tracking"
depends on CPU_SUP_INTEL && HAVE_CALL_THUNKS
select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
select CALL_THUNKS
default y
help
Compile the kernel with call depth tracking to mitigate the Intel
SKL Return-Speculation-Buffer (RSB) underflow issue. The
mitigation is off by default and needs to be enabled on the
kernel command line via the retbleed=stuff option. For
non-affected systems the overhead of this option is marginal as
the call depth tracking is using run-time generated call thunks
in a compiler generated padding area and call patching. This
increases text size by ~5%. For non affected systems this space
is unused. On affected SKL systems this results in a significant
performance gain over the IBRS mitigation.
config CALL_THUNKS_DEBUG
bool "Enable call thunks and call depth tracking debugging"
depends on MITIGATION_CALL_DEPTH_TRACKING
select FUNCTION_ALIGNMENT_32B
default n
help
Enable call/ret counters for imbalance detection and build in
a noisy dmesg about callthunks generation and call patching for
trouble shooting. The debug prints need to be enabled on the
kernel command line with 'debug-callthunks'.
Only enable this when you are debugging call thunks as this
creates a noticeable runtime overhead. If unsure say N.
config MITIGATION_IBPB_ENTRY
bool "Enable IBPB on kernel entry"
depends on CPU_SUP_AMD && X86_64
default y
help
Compile the kernel with support for the retbleed=ibpb mitigation.
config MITIGATION_IBRS_ENTRY
bool "Enable IBRS on kernel entry"
depends on CPU_SUP_INTEL && X86_64
default y
help
Compile the kernel with support for the spectre_v2=ibrs mitigation.
This mitigates both spectre_v2 and retbleed at great cost to
performance.
config MITIGATION_SRSO
bool "Mitigate speculative RAS overflow on AMD"
depends on CPU_SUP_AMD && X86_64 && MITIGATION_RETHUNK
default y
help
Enable the SRSO mitigation needed on AMD Zen1-4 machines.
config MITIGATION_SLS
bool "Mitigate Straight-Line-Speculation"
depends on CC_HAS_SLS && X86_64
select OBJTOOL if HAVE_OBJTOOL
default n
help
Compile the kernel with straight-line-speculation options to guard
against straight line speculation. The kernel image might be slightly
larger.
config MITIGATION_GDS_FORCE
bool "Force GDS Mitigation"
depends on CPU_SUP_INTEL
default n
help
Gather Data Sampling (GDS) is a hardware vulnerability which allows
unprivileged speculative access to data which was previously stored in
vector registers.
This option is equivalent to setting gather_data_sampling=force on the
command line. The microcode mitigation is used if present, otherwise
AVX is disabled as a mitigation. On affected systems that are missing
the microcode any userspace code that unconditionally uses AVX will
break with this option set.
Setting this option on systems not vulnerable to GDS has no effect.
If in doubt, say N.
config MITIGATION_RFDS
bool "RFDS Mitigation"
depends on CPU_SUP_INTEL
default y
help
Enable mitigation for Register File Data Sampling (RFDS) by default.
RFDS is a hardware vulnerability which affects Intel Atom CPUs. It
allows unprivileged speculative access to stale data previously
stored in floating point, vector and integer registers.
See also <file:Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst>
config MITIGATION_SPECTRE_BHI
bool "Mitigate Spectre-BHB (Branch History Injection)"
depends on CPU_SUP_INTEL
default y
help
Enable BHI mitigations. BHI attacks are a form of Spectre V2 attacks
where the branch history buffer is poisoned to speculatively steer
indirect branches.
See <file:Documentation/admin-guide/hw-vuln/spectre.rst>
endif
config ARCH_HAS_ADD_PAGES
def_bool y
depends on ARCH_ENABLE_MEMORY_HOTPLUG
menu "Power management and ACPI options"
config ARCH_HIBERNATION_HEADER
def_bool y
depends on HIBERNATION
source "kernel/power/Kconfig"
source "drivers/acpi/Kconfig"
config X86_APM_BOOT
def_bool y
depends on APM
menuconfig APM
tristate "APM (Advanced Power Management) BIOS support"
depends on X86_32 && PM_SLEEP
help
APM is a BIOS specification for saving power using several different
techniques. This is mostly useful for battery powered laptops with
APM compliant BIOSes. If you say Y here, the system time will be
reset after a RESUME operation, the /proc/apm device will provide
battery status information, and user-space programs will receive
notification of APM "events" (e.g. battery status change).
If you select "Y" here, you can disable actual use of the APM
BIOS by passing the "apm=off" option to the kernel at boot time.
Note that the APM support is almost completely disabled for
machines with more than one CPU.
In order to use APM, you will need supporting software. For location
and more information, read <file:Documentation/power/apm-acpi.rst>
and the Battery Powered Linux mini-HOWTO, available from
<http://www.tldp.org/docs.html#howto>.
This driver does not spin down disk drives (see the hdparm(8)
manpage ("man 8 hdparm") for that), and it doesn't turn off
VESA-compliant "green" monitors.
This driver does not support the TI 4000M TravelMate and the ACER
486/DX4/75 because they don't have compliant BIOSes. Many "green"
desktop machines also don't have compliant BIOSes, and this driver
may cause those machines to panic during the boot phase.
Generally, if you don't have a battery in your machine, there isn't
much point in using this driver and you should say N. If you get
random kernel OOPSes or reboots that don't seem to be related to
anything, try disabling/enabling this option (or disabling/enabling
APM in your BIOS).
Some other things you should try when experiencing seemingly random,
"weird" problems:
1) make sure that you have enough swap space and that it is
enabled.
2) pass the "idle=poll" option to the kernel
3) switch on floating point emulation in the kernel and pass
the "no387" option to the kernel
4) pass the "floppy=nodma" option to the kernel
5) pass the "mem=4M" option to the kernel (thereby disabling
all but the first 4 MB of RAM)
6) make sure that the CPU is not over clocked.
7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
8) disable the cache from your BIOS settings
9) install a fan for the video card or exchange video RAM
10) install a better fan for the CPU
11) exchange RAM chips
12) exchange the motherboard.
To compile this driver as a module, choose M here: the
module will be called apm.
if APM
config APM_IGNORE_USER_SUSPEND
bool "Ignore USER SUSPEND"
help
This option will ignore USER SUSPEND requests. On machines with a
compliant APM BIOS, you want to say N. However, on the NEC Versa M
series notebooks, it is necessary to say Y because of a BIOS bug.
config APM_DO_ENABLE
bool "Enable PM at boot time"
help
Enable APM features at boot time. From page 36 of the APM BIOS
specification: "When disabled, the APM BIOS does not automatically
power manage devices, enter the Standby State, enter the Suspend
State, or take power saving steps in response to CPU Idle calls."
This driver will make CPU Idle calls when Linux is idle (unless this
feature is turned off -- see "Do CPU IDLE calls", below). This
should always save battery power, but more complicated APM features
will be dependent on your BIOS implementation. You may need to turn
this option off if your computer hangs at boot time when using APM
support, or if it beeps continuously instead of suspending. Turn
this off if you have a NEC UltraLite Versa 33/C or a Toshiba
T400CDT. This is off by default since most machines do fine without
this feature.
config APM_CPU_IDLE
depends on CPU_IDLE
bool "Make CPU Idle calls when idle"
help
Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
On some machines, this can activate improved power savings, such as
a slowed CPU clock rate, when the machine is idle. These idle calls
are made after the idle loop has run for some length of time (e.g.,
333 mS). On some machines, this will cause a hang at boot time or
whenever the CPU becomes idle. (On machines with more than one CPU,
this option does nothing.)
config APM_DISPLAY_BLANK
bool "Enable console blanking using APM"
help
Enable console blanking using the APM. Some laptops can use this to
turn off the LCD backlight when the screen blanker of the Linux
virtual console blanks the screen. Note that this is only used by
the virtual console screen blanker, and won't turn off the backlight
when using the X Window system. This also doesn't have anything to
do with your VESA-compliant power-saving monitor. Further, this
option doesn't work for all laptops -- it might not turn off your
backlight at all, or it might print a lot of errors to the console,
especially if you are using gpm.
config APM_ALLOW_INTS
bool "Allow interrupts during APM BIOS calls"
help
Normally we disable external interrupts while we are making calls to
the APM BIOS as a measure to lessen the effects of a badly behaving
BIOS implementation. The BIOS should reenable interrupts if it
needs to. Unfortunately, some BIOSes do not -- especially those in
many of the newer IBM Thinkpads. If you experience hangs when you
suspend, try setting this to Y. Otherwise, say N.
endif # APM
source "drivers/cpufreq/Kconfig"
source "drivers/cpuidle/Kconfig"
source "drivers/idle/Kconfig"
endmenu
menu "Bus options (PCI etc.)"
choice
prompt "PCI access mode"
depends on X86_32 && PCI
default PCI_GOANY
help
On PCI systems, the BIOS can be used to detect the PCI devices and
determine their configuration. However, some old PCI motherboards
have BIOS bugs and may crash if this is done. Also, some embedded
PCI-based systems don't have any BIOS at all. Linux can also try to
detect the PCI hardware directly without using the BIOS.
With this option, you can specify how Linux should detect the
PCI devices. If you choose "BIOS", the BIOS will be used,
if you choose "Direct", the BIOS won't be used, and if you
choose "MMConfig", then PCI Express MMCONFIG will be used.
If you choose "Any", the kernel will try MMCONFIG, then the
direct access method and falls back to the BIOS if that doesn't
work. If unsure, go with the default, which is "Any".
config PCI_GOBIOS
bool "BIOS"
config PCI_GOMMCONFIG
bool "MMConfig"
config PCI_GODIRECT
bool "Direct"
config PCI_GOOLPC
bool "OLPC XO-1"
depends on OLPC
config PCI_GOANY
bool "Any"
endchoice
config PCI_BIOS
def_bool y
depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
# x86-64 doesn't support PCI BIOS access from long mode so always go direct.
config PCI_DIRECT
def_bool y
depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
config PCI_MMCONFIG
bool "Support mmconfig PCI config space access" if X86_64
default y
depends on PCI && (ACPI || JAILHOUSE_GUEST)
depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
config PCI_OLPC
def_bool y
depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
config PCI_XEN
def_bool y
depends on PCI && XEN
config MMCONF_FAM10H
def_bool y
depends on X86_64 && PCI_MMCONFIG && ACPI
config PCI_CNB20LE_QUIRK
bool "Read CNB20LE Host Bridge Windows" if EXPERT
depends on PCI
help
Read the PCI windows out of the CNB20LE host bridge. This allows
PCI hotplug to work on systems with the CNB20LE chipset which do
not have ACPI.
There's no public spec for this chipset, and this functionality
is known to be incomplete.
You should say N unless you know you need this.
config ISA_BUS
bool "ISA bus support on modern systems" if EXPERT
help
Expose ISA bus device drivers and options available for selection and
configuration. Enable this option if your target machine has an ISA
bus. ISA is an older system, displaced by PCI and newer bus
architectures -- if your target machine is modern, it probably does
not have an ISA bus.
If unsure, say N.
# x86_64 have no ISA slots, but can have ISA-style DMA.
config ISA_DMA_API
bool "ISA-style DMA support" if (X86_64 && EXPERT)
default y
help
Enables ISA-style DMA support for devices requiring such controllers.
If unsure, say Y.
if X86_32
config ISA
bool "ISA support"
help
Find out whether you have ISA slots on your motherboard. ISA is the
name of a bus system, i.e. the way the CPU talks to the other stuff
inside your box. Other bus systems are PCI, EISA, MicroChannel
(MCA) or VESA. ISA is an older system, now being displaced by PCI;
newer boards don't support it. If you have ISA, say Y, otherwise N.
config SCx200
tristate "NatSemi SCx200 support"
help
This provides basic support for National Semiconductor's
(now AMD's) Geode processors. The driver probes for the
PCI-IDs of several on-chip devices, so its a good dependency
for other scx200_* drivers.
If compiled as a module, the driver is named scx200.
config SCx200HR_TIMER
tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
depends on SCx200
default y
help
This driver provides a clocksource built upon the on-chip
27MHz high-resolution timer. Its also a workaround for
NSC Geode SC-1100's buggy TSC, which loses time when the
processor goes idle (as is done by the scheduler). The
other workaround is idle=poll boot option.
config OLPC
bool "One Laptop Per Child support"
depends on !X86_PAE
select GPIOLIB
select OF
select OF_PROMTREE
select IRQ_DOMAIN
select OLPC_EC
help
Add support for detecting the unique features of the OLPC
XO hardware.
config OLPC_XO1_PM
bool "OLPC XO-1 Power Management"
depends on OLPC && MFD_CS5535=y && PM_SLEEP
help
Add support for poweroff and suspend of the OLPC XO-1 laptop.
config OLPC_XO1_RTC
bool "OLPC XO-1 Real Time Clock"
depends on OLPC_XO1_PM && RTC_DRV_CMOS
help
Add support for the XO-1 real time clock, which can be used as a
programmable wakeup source.
config OLPC_XO1_SCI
bool "OLPC XO-1 SCI extras"
depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
depends on INPUT=y
select POWER_SUPPLY
help
Add support for SCI-based features of the OLPC XO-1 laptop:
- EC-driven system wakeups
- Power button
- Ebook switch
- Lid switch
- AC adapter status updates
- Battery status updates
config OLPC_XO15_SCI
bool "OLPC XO-1.5 SCI extras"
depends on OLPC && ACPI
select POWER_SUPPLY
help
Add support for SCI-based features of the OLPC XO-1.5 laptop:
- EC-driven system wakeups
- AC adapter status updates
- Battery status updates
config ALIX
bool "PCEngines ALIX System Support (LED setup)"
select GPIOLIB
help
This option enables system support for the PCEngines ALIX.
At present this just sets up LEDs for GPIO control on
ALIX2/3/6 boards. However, other system specific setup should
get added here.
Note: You must still enable the drivers for GPIO and LED support
(GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
Note: You have to set alix.force=1 for boards with Award BIOS.
config NET5501
bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
select GPIOLIB
help
This option enables system support for the Soekris Engineering net5501.
config GEOS
bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
select GPIOLIB
depends on DMI
help
This option enables system support for the Traverse Technologies GEOS.
config TS5500
bool "Technologic Systems TS-5500 platform support"
depends on MELAN
select CHECK_SIGNATURE
select NEW_LEDS
select LEDS_CLASS
help
This option enables system support for the Technologic Systems TS-5500.
endif # X86_32
config AMD_NB
def_bool y
depends on CPU_SUP_AMD && PCI
endmenu
menu "Binary Emulations"
config IA32_EMULATION
bool "IA32 Emulation"
depends on X86_64
select ARCH_WANT_OLD_COMPAT_IPC
select BINFMT_ELF
select COMPAT_OLD_SIGACTION
help
Include code to run legacy 32-bit programs under a
64-bit kernel. You should likely turn this on, unless you're
100% sure that you don't have any 32-bit programs left.
config IA32_EMULATION_DEFAULT_DISABLED
bool "IA32 emulation disabled by default"
default n
depends on IA32_EMULATION
help
Make IA32 emulation disabled by default. This prevents loading 32-bit
processes and access to 32-bit syscalls. If unsure, leave it to its
default value.
config X86_X32_ABI
bool "x32 ABI for 64-bit mode"
depends on X86_64
# llvm-objcopy does not convert x86_64 .note.gnu.property or
# compressed debug sections to x86_x32 properly:
# https://github.com/ClangBuiltLinux/linux/issues/514
# https://github.com/ClangBuiltLinux/linux/issues/1141
depends on $(success,$(OBJCOPY) --version | head -n1 | grep -qv llvm)
help
Include code to run binaries for the x32 native 32-bit ABI
for 64-bit processors. An x32 process gets access to the
full 64-bit register file and wide data path while leaving
pointers at 32 bits for smaller memory footprint.
config COMPAT_32
def_bool y
depends on IA32_EMULATION || X86_32
select HAVE_UID16
select OLD_SIGSUSPEND3
config COMPAT
def_bool y
depends on IA32_EMULATION || X86_X32_ABI
config COMPAT_FOR_U64_ALIGNMENT
def_bool y
depends on COMPAT
endmenu
config HAVE_ATOMIC_IOMAP
def_bool y
depends on X86_32
source "arch/x86/kvm/Kconfig"
source "arch/x86/Kconfig.assembler"
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