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linux/arch/x86/kernel
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Linus Torvalds 093d9603b6 x86: stop playing stack games in profile_pc() 
The 'profile_pc()' function is used for timer-based profiling, which
isn't really all that relevant any more to begin with, but it also ends
up making assumptions based on the stack layout that aren't necessarily
valid.

Basically, the code tries to account the time spent in spinlocks to the
caller rather than the spinlock, and while I support that as a concept,
it's not worth the code complexity or the KASAN warnings when no serious
profiling is done using timers anyway these days.

And the code really does depend on stack layout that is only true in the
simplest of cases.  We've lost the comment at some point (I think when
the 32-bit and 64-bit code was unified), but it used to say:

	Assume the lock function has either no stack frame or a copy
	of eflags from PUSHF.

which explains why it just blindly loads a word or two straight off the
stack pointer and then takes a minimal look at the values to just check
if they might be eflags or the return pc:

	Eflags always has bits 22 and up cleared unlike kernel addresses

but that basic stack layout assumption assumes that there isn't any lock
debugging etc going on that would complicate the code and cause a stack
frame.

It causes KASAN unhappiness reported for years by syzkaller [1] and
others [2].

With no real practical reason for this any more, just remove the code.

Just for historical interest, here's some background commits relating to
this code from 2006:

  0cb91a2293 ("i386: Account spinlocks to the caller during profiling for !FP kernels")
  31679f38d8 ("Simplify profile_pc on x86-64")

and a code unification from 2009:

  ef4512882d ("x86: time_32/64.c unify profile_pc")

but the basics of this thing actually goes back to before the git tree.

Link: https://syzkaller.appspot.com/bug?extid=84fe685c02cd112a2ac3 [1]
Link: https://lore.kernel.org/all/CAK55_s7Xyq=nh97=K=G1sxueOFrJDAvPOJAL4TPTCAYvmxO9_A@mail.gmail.com/ [2]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2024-06-28 14:27:22 -07:00
..
acpi ACPI updates for 6.9-rc1 2024-03-13 11:54:05 -07:00
apic genirq/cpuhotplug, x86/vector: Prevent vector leak during CPU offline 2024-05-23 21:51:50 +02:00
cpu x86/resctrl: Don't try to free nonexistent RMIDs 2024-06-19 11:39:09 +02:00
fpu ARM: 2024-05-15 14:46:43 -07:00
kprobes Probes updates for v6.10: 2024-05-17 18:29:30 -07:00
.gitignore
alternative.c x86/alternatives: Use the correct length when optimizing NOPs 2024-05-17 09:27:06 +02:00
amd_gart_64.c change alloc_pages name in dma_map_ops to avoid name conflicts 2024-04-25 20:55:53 -07:00
amd_nb.c x86/amd_nb: Check for invalid SMN reads 2024-06-05 21:23:34 +02:00
aperture_64.c x86/pci: Use PCI_HEADER_TYPE_* instead of literals 2023-12-01 15:00:43 -06:00
apm_32.c x86/apm_32: Remove dead function apm_get_battery_status() 2024-02-21 19:38:03 +01:00
asm-offsets_32.c
asm-offsets_64.c x86: Fixup asm-offsets duplicate 2022-10-17 16:41:06 +02:00
asm-offsets.c x86/bugs: Rename CONFIG_CALL_DEPTH_TRACKING => CONFIG_MITIGATION_CALL_DEPTH_TRACKING 2024-01-10 10:52:28 +01:00
audit_64.c x86/audit: Fix -Wmissing-variable-declarations warning for ia32_xyz_class 2023-08-30 10:11:16 +02:00
bootflag.c
callthunks.c x86/alternatives: Use a temporary buffer when optimizing NOPs 2024-04-09 18:08:11 +02:00
cet.c x86/ibt: Convert IBT selftest to asm 2023-08-17 17:07:09 +02:00
cfi.c cfi: Flip headers 2023-12-15 16:25:55 -08:00
check.c
cpuid.c x86/cpuid: make cpuid_class a static const structure 2023-08-05 08:31:41 +02:00
crash_dump_32.c
crash_dump_64.c use less confusing names for iov_iter direction initializers 2022-11-25 13:01:55 -05:00
crash.c crash: add a new kexec flag for hotplug support 2024-04-23 14:59:01 +10:00
devicetree.c x86/of: Change x86_dtb_parse_smp_config() to static 2024-04-03 08:49:56 +02:00
doublefault_32.c x86: Avoid missing-prototype warnings for doublefault code 2023-05-18 11:56:18 -07:00
dumpstack_32.c x86/percpu: Move irq_stack variables next to current_task 2022-10-17 16:41:05 +02:00
dumpstack_64.c x86/percpu: Move irq_stack variables next to current_task 2022-10-17 16:41:05 +02:00
dumpstack.c x86/dumpstack: Use uniform "Oops: " prefix for die() messages 2024-03-27 08:45:19 +01:00
e820.c x86/e820: Add a new e820 table update helper 2024-04-29 11:15:31 +02:00
early_printk.c
early-quirks.c x86/pci: Use PCI_HEADER_TYPE_* instead of literals 2023-12-01 15:00:43 -06:00
ebda.c
eisa.c x86/sev: Skip ROM range scans and validation for SEV-SNP guests 2024-03-26 15:22:35 +01:00
espfix_64.c x86/fred: No ESPFIX needed when FRED is enabled 2024-01-31 22:01:51 +01:00
fred.c x86/fred: Add FRED initialization functions 2024-01-31 22:03:32 +01:00
ftrace_32.S x86/headers: Replace #include <asm/export.h> with #include <linux/export.h> 2023-10-03 10:38:07 +02:00
ftrace_64.S x86/headers: Replace #include <asm/export.h> with #include <linux/export.h> 2023-10-03 10:38:07 +02:00
ftrace.c x86/ftrace: enable dynamic ftrace without CONFIG_MODULES 2024-05-14 00:31:44 -07:00
head32.c x86/microcode/32: Move early loading after paging enable 2023-10-18 22:15:01 +02:00
head64.c x86/boot/64: Move 5-level paging global variable assignments back 2024-03-24 05:00:36 +01:00
head_32.S x86/cleanups changes for v6.10: 2024-05-13 18:21:24 -07:00
head_64.S x86/cleanups changes for v6.10: 2024-05-13 18:21:24 -07:00
hpet.c x86/apic/msi: Use DOMAIN_BUS_GENERIC_MSI for HPET/IO-APIC domain search 2024-02-25 18:53:08 +01:00
hw_breakpoint.c x86/amd: Cache debug register values in percpu variables 2023-01-31 20:09:26 +01:00
i8237.c
i8253.c
i8259.c x86/i8259: Skip probing when ACPI/MADT advertises PCAT compatibility 2023-10-27 20:36:49 +02:00
ibt_selftest.S x86/ibt: Convert IBT selftest to asm 2023-08-17 17:07:09 +02:00
idt.c x86/irq: Install posted MSI notification handler 2024-04-30 00:54:42 +02:00
io_delay.c
ioport.c
irq_32.c x86/percpu: Move irq_stack variables next to current_task 2022-10-17 16:41:05 +02:00
irq_64.c fix missing vmalloc.h includes 2024-04-25 20:55:49 -07:00
irq_work.c x86/apic: Wrap IPI calls into helper functions 2023-08-09 12:00:55 -07:00
irq.c x86/irq: Factor out common code for checking pending interrupts 2024-04-30 00:54:43 +02:00
irqflags.S x86/headers: Replace #include <asm/export.h> with #include <linux/export.h> 2023-10-03 10:38:07 +02:00
irqinit.c x86/fred: Invoke FRED initialization code to enable FRED 2024-01-31 22:03:36 +01:00
itmt.c arch/x86: Remove now superfluous sentinel elem from ctl_table arrays 2023-10-10 15:22:02 -07:00
jailhouse.c x86/jailhouse: Use new APIC registration function 2024-02-15 22:07:42 +01:00
jump_label.c
kdebugfs.c
kexec-bzimage64.c - Sumanth Korikkar has taught s390 to allocate hotplug-time page frames 2024-03-14 17:43:30 -07:00
kgdb.c x86/kgdb: Fix a kerneldoc warning when build with W=1 2023-09-24 11:00:13 +02:00
ksysfs.c
kvm.c Linux 6.9-rc3 2024-04-09 09:48:09 +02:00
kvmclock.c kvmclock: Unexport kvmclock clocksource 2024-02-07 17:05:21 +01:00
ldt.c x86/bugs: Rename CONFIG_PAGE_TABLE_ISOLATION => CONFIG_MITIGATION_PAGE_TABLE_ISOLATION 2024-01-10 10:52:28 +01:00
machine_kexec_32.c
machine_kexec_64.c x86/kexec: Fix bug with call depth tracking 2024-06-03 17:19:03 +02:00
Makefile Kbuild updates for v6.10 2024-05-18 12:39:20 -07:00
mmconf-fam10h_64.c
module.c arch: make execmem setup available regardless of CONFIG_MODULES 2024-05-14 00:31:44 -07:00
mpparse.c x86/mpparse: Register APIC address only once 2024-03-23 12:41:48 +01:00
msr.c x86/MSR: make msr_class a static const structure 2023-08-05 08:31:42 +02:00
nmi_selftest.c x86/apic: Wrap IPI calls into helper functions 2023-08-09 12:00:55 -07:00
nmi.c x86/nmi: Upgrade NMI backtrace stall checks & messages 2024-03-26 10:07:59 +01:00
paravirt-spinlocks.c
paravirt.c x86/paravirt: Remove no longer needed paravirt patching code 2023-12-10 23:34:37 +01:00
pci-dma.c x86: always initialize xen-swiotlb when xen-pcifront is enabling 2023-07-31 17:54:27 +02:00
pcspeaker.c
perf_regs.c
platform-quirks.c x86/quirks: Include linux/pnp.h for arch_pnpbios_disabled() 2023-05-18 11:56:18 -07:00
pmem.c
probe_roms.c x86/sev: Skip ROM range scans and validation for SEV-SNP guests 2024-03-26 15:22:35 +01:00
process_32.c x86/fpu: Clean up FPU switching in the middle of task switching 2023-10-20 11:24:22 +02:00
process_64.c x86/cpu: Fix check for RDPKRU in __show_regs() 2024-04-24 14:30:21 +02:00
process.c Core x86 changes for v6.9: 2024-03-11 19:53:15 -07:00
process.h
ptrace.c x86: Add PTRACE interface for shadow stack 2023-08-02 15:01:51 -07:00
pvclock.c locking/atomic: treewide: use raw_atomic*_<op>() 2023-06-05 09:57:20 +02:00
quirks.c
reboot_fixups_32.c
reboot.c x86, crash: wrap crash dumping code into crash related ifdefs 2024-02-23 17:48:23 -08:00
relocate_kernel_32.S
relocate_kernel_64.S x86,objtool: Split UNWIND_HINT_EMPTY in two 2023-03-23 23:18:58 +01:00
resource.c x86/PCI: Tidy E820 removal messages 2022-12-10 10:33:11 -06:00
rethook.c
rtc.c x86/rtc: Remove unused intel-mid.h 2024-04-03 08:24:48 -07:00
setup_percpu.c x86/asm: Add DB flag to 32-bit percpu GDT entry 2023-12-20 10:57:51 +01:00
setup.c The usual shower of singleton fixes and minor series all over MM, 2024-05-19 09:21:03 -07:00
sev_verify_cbit.S x86/boot: Use 32-bit XOR to clear registers 2024-03-01 12:47:37 +01:00
sev-shared.c x86/sev: Check for MWAITX and MONITORX opcodes in the #VC handler 2024-04-22 18:38:28 +02:00
sev.c - Small cleanups and improvements 2024-05-14 09:18:52 -07:00
shstk.c x86/shstk: Enable shadow stacks for x32 2024-03-22 10:17:11 +01:00
signal_32.c x86/syscall/compat: Remove ia32_unistd.h 2024-03-22 09:37:09 +01:00
signal_64.c x86/shstk: Enable shadow stacks for x32 2024-03-22 10:17:11 +01:00
signal.c rseq: Split out rseq.h from sched.h 2023-12-27 11:49:56 -05:00
smp.c - Sumanth Korikkar has taught s390 to allocate hotplug-time page frames 2024-03-14 17:43:30 -07:00
smpboot.c x86/cpu: Switch to new Intel CPU model defines 2024-04-29 10:31:30 +02:00
stacktrace.c
static_call.c x86/bugs: Rename CONFIG_RETHUNK => CONFIG_MITIGATION_RETHUNK 2024-01-10 10:52:29 +01:00
step.c x86/msr: Prepare for including <linux/percpu.h> into <asm/msr.h> 2024-03-04 12:01:39 +01:00
sys_ia32.c
sys_x86_64.c x86/mm: care about shadow stack guard gap during placement 2024-04-25 20:56:28 -07:00
tboot.c
time.c x86: stop playing stack games in profile_pc() 2024-06-28 14:27:22 -07:00
tls.c x86/gsseg: Move load_gs_index() to its own new header file 2023-01-12 13:06:36 +01:00
tls.h
trace_clock.c
trace.c
tracepoint.c
traps.c Core x86 changes for v6.9: 2024-03-11 19:53:15 -07:00
tsc_msr.c x86/tsc_msr: Switch to new Intel CPU model defines 2024-04-29 10:31:34 +02:00
tsc_sync.c x86/tsc: Trust initial offset in architectural TSC-adjust MSRs 2024-04-29 23:27:16 +02:00
tsc.c x86/cpu changes for v6.10: 2024-05-13 18:44:44 -07:00
umip.c
unwind_frame.c
unwind_guess.c
unwind_orc.c x86/unwind/orc: Remove redundant initialization of 'mid' pointer in __orc_find() 2023-09-21 08:41:23 +02:00
uprobes.c uprobes/x86: Allow to probe a NOP instruction with 0x66 prefix 2022-12-05 11:55:18 +01:00
verify_cpu.S
vm86_32.c
vmcore_info_32.c crash: split vmcoreinfo exporting code out from crash_core.c 2024-02-23 17:48:22 -08:00
vmcore_info_64.c crash: split vmcoreinfo exporting code out from crash_core.c 2024-02-23 17:48:22 -08:00
vmlinux.lds.S x86/build changes for v6.10: 2024-05-13 18:05:08 -07:00
vsmp_64.c x86/apic: Remove unused phys_pkg_id() callback 2024-02-15 22:07:38 +01:00
x86_init.c x86/sev: Skip ROM range scans and validation for SEV-SNP guests 2024-03-26 15:22:35 +01:00