From 3891a04aafd668686239349ea58f3314ea2af86b Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Tue, 29 Apr 2014 16:46:09 -0700 Subject: [PATCH 1/7] x86-64, espfix: Don't leak bits 31:16 of %esp returning to 16-bit stack The IRET instruction, when returning to a 16-bit segment, only restores the bottom 16 bits of the user space stack pointer. This causes some 16-bit software to break, but it also leaks kernel state to user space. We have a software workaround for that ("espfix") for the 32-bit kernel, but it relies on a nonzero stack segment base which is not available in 64-bit mode. In checkin: b3b42ac2cbae x86-64, modify_ldt: Ban 16-bit segments on 64-bit kernels we "solved" this by forbidding 16-bit segments on 64-bit kernels, with the logic that 16-bit support is crippled on 64-bit kernels anyway (no V86 support), but it turns out that people are doing stuff like running old Win16 binaries under Wine and expect it to work. This works around this by creating percpu "ministacks", each of which is mapped 2^16 times 64K apart. When we detect that the return SS is on the LDT, we copy the IRET frame to the ministack and use the relevant alias to return to userspace. The ministacks are mapped readonly, so if IRET faults we promote #GP to #DF which is an IST vector and thus has its own stack; we then do the fixup in the #DF handler. (Making #GP an IST exception would make the msr_safe functions unsafe in NMI/MC context, and quite possibly have other effects.) Special thanks to: - Andy Lutomirski, for the suggestion of using very small stack slots and copy (as opposed to map) the IRET frame there, and for the suggestion to mark them readonly and let the fault promote to #DF. - Konrad Wilk for paravirt fixup and testing. - Borislav Petkov for testing help and useful comments. Reported-by: Brian Gerst Signed-off-by: H. Peter Anvin Link: http://lkml.kernel.org/r/1398816946-3351-1-git-send-email-hpa@linux.intel.com Cc: Konrad Rzeszutek Wilk Cc: Borislav Petkov Cc: Andrew Lutomriski Cc: Linus Torvalds Cc: Dirk Hohndel Cc: Arjan van de Ven Cc: comex Cc: Alexander van Heukelum Cc: Boris Ostrovsky Cc: # consider after upstream merge --- Documentation/x86/x86_64/mm.txt | 2 + arch/x86/include/asm/pgtable_64_types.h | 2 + arch/x86/include/asm/setup.h | 3 + arch/x86/kernel/Makefile | 1 + arch/x86/kernel/entry_64.S | 73 ++++++++- arch/x86/kernel/espfix_64.c | 208 ++++++++++++++++++++++++ arch/x86/kernel/ldt.c | 11 -- arch/x86/kernel/smpboot.c | 7 + arch/x86/mm/dump_pagetables.c | 42 +++-- init/main.c | 4 + 10 files changed, 328 insertions(+), 25 deletions(-) create mode 100644 arch/x86/kernel/espfix_64.c diff --git a/Documentation/x86/x86_64/mm.txt b/Documentation/x86/x86_64/mm.txt index c584a51add15..afe68ddbe6a4 100644 --- a/Documentation/x86/x86_64/mm.txt +++ b/Documentation/x86/x86_64/mm.txt @@ -12,6 +12,8 @@ ffffc90000000000 - ffffe8ffffffffff (=45 bits) vmalloc/ioremap space ffffe90000000000 - ffffe9ffffffffff (=40 bits) hole ffffea0000000000 - ffffeaffffffffff (=40 bits) virtual memory map (1TB) ... unused hole ... +ffffff0000000000 - ffffff7fffffffff (=39 bits) %esp fixup stacks +... unused hole ... ffffffff80000000 - ffffffffa0000000 (=512 MB) kernel text mapping, from phys 0 ffffffffa0000000 - ffffffffff5fffff (=1525 MB) module mapping space ffffffffff600000 - ffffffffffdfffff (=8 MB) vsyscalls diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h index c883bf726398..7166e25ecb57 100644 --- a/arch/x86/include/asm/pgtable_64_types.h +++ b/arch/x86/include/asm/pgtable_64_types.h @@ -61,6 +61,8 @@ typedef struct { pteval_t pte; } pte_t; #define MODULES_VADDR (__START_KERNEL_map + KERNEL_IMAGE_SIZE) #define MODULES_END _AC(0xffffffffff000000, UL) #define MODULES_LEN (MODULES_END - MODULES_VADDR) +#define ESPFIX_PGD_ENTRY _AC(-2, UL) +#define ESPFIX_BASE_ADDR (ESPFIX_PGD_ENTRY << PGDIR_SHIFT) #define EARLY_DYNAMIC_PAGE_TABLES 64 diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h index 9264f04a4c55..9e3be3329a7e 100644 --- a/arch/x86/include/asm/setup.h +++ b/arch/x86/include/asm/setup.h @@ -57,6 +57,9 @@ extern void x86_ce4100_early_setup(void); static inline void x86_ce4100_early_setup(void) { } #endif +extern void init_espfix_bsp(void); +extern void init_espfix_ap(void); + #ifndef _SETUP /* diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index f4d96000d33a..1cc3789d99d9 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -29,6 +29,7 @@ obj-$(CONFIG_X86_64) += sys_x86_64.o x8664_ksyms_64.o obj-y += syscall_$(BITS).o vsyscall_gtod.o obj-$(CONFIG_X86_64) += vsyscall_64.o obj-$(CONFIG_X86_64) += vsyscall_emu_64.o +obj-$(CONFIG_X86_64) += espfix_64.o obj-$(CONFIG_SYSFS) += ksysfs.o obj-y += bootflag.o e820.o obj-y += pci-dma.o quirks.o topology.o kdebugfs.o diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 1e96c3628bf2..bffaa986cafc 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -58,6 +58,7 @@ #include #include #include +#include #include /* Avoid __ASSEMBLER__'ifying just for this. */ @@ -1040,8 +1041,16 @@ restore_args: RESTORE_ARGS 1,8,1 irq_return: + /* + * Are we returning to a stack segment from the LDT? Note: in + * 64-bit mode SS:RSP on the exception stack is always valid. + */ + testb $4,(SS-RIP)(%rsp) + jnz irq_return_ldt + +irq_return_iret: INTERRUPT_RETURN - _ASM_EXTABLE(irq_return, bad_iret) + _ASM_EXTABLE(irq_return_iret, bad_iret) #ifdef CONFIG_PARAVIRT ENTRY(native_iret) @@ -1049,6 +1058,30 @@ ENTRY(native_iret) _ASM_EXTABLE(native_iret, bad_iret) #endif +irq_return_ldt: + pushq_cfi %rax + pushq_cfi %rdi + SWAPGS + movq PER_CPU_VAR(espfix_waddr),%rdi + movq %rax,(0*8)(%rdi) /* RAX */ + movq (2*8)(%rsp),%rax /* RIP */ + movq %rax,(1*8)(%rdi) + movq (3*8)(%rsp),%rax /* CS */ + movq %rax,(2*8)(%rdi) + movq (4*8)(%rsp),%rax /* RFLAGS */ + movq %rax,(3*8)(%rdi) + movq (6*8)(%rsp),%rax /* SS */ + movq %rax,(5*8)(%rdi) + movq (5*8)(%rsp),%rax /* RSP */ + movq %rax,(4*8)(%rdi) + andl $0xffff0000,%eax + popq_cfi %rdi + orq PER_CPU_VAR(espfix_stack),%rax + SWAPGS + movq %rax,%rsp + popq_cfi %rax + jmp irq_return_iret + .section .fixup,"ax" bad_iret: /* @@ -1110,9 +1143,41 @@ ENTRY(retint_kernel) call preempt_schedule_irq jmp exit_intr #endif - CFI_ENDPROC END(common_interrupt) + + /* + * If IRET takes a fault on the espfix stack, then we + * end up promoting it to a doublefault. In that case, + * modify the stack to make it look like we just entered + * the #GP handler from user space, similar to bad_iret. + */ + ALIGN +__do_double_fault: + XCPT_FRAME 1 RDI+8 + movq RSP(%rdi),%rax /* Trap on the espfix stack? */ + sarq $PGDIR_SHIFT,%rax + cmpl $ESPFIX_PGD_ENTRY,%eax + jne do_double_fault /* No, just deliver the fault */ + cmpl $__KERNEL_CS,CS(%rdi) + jne do_double_fault + movq RIP(%rdi),%rax + cmpq $irq_return_iret,%rax +#ifdef CONFIG_PARAVIRT + je 1f + cmpq $native_iret,%rax +#endif + jne do_double_fault /* This shouldn't happen... */ +1: + movq PER_CPU_VAR(kernel_stack),%rax + subq $(6*8-KERNEL_STACK_OFFSET),%rax /* Reset to original stack */ + movq %rax,RSP(%rdi) + movq $0,(%rax) /* Missing (lost) #GP error code */ + movq $general_protection,RIP(%rdi) + retq + CFI_ENDPROC +END(__do_double_fault) + /* * End of kprobes section */ @@ -1314,7 +1379,7 @@ zeroentry overflow do_overflow zeroentry bounds do_bounds zeroentry invalid_op do_invalid_op zeroentry device_not_available do_device_not_available -paranoiderrorentry double_fault do_double_fault +paranoiderrorentry double_fault __do_double_fault zeroentry coprocessor_segment_overrun do_coprocessor_segment_overrun errorentry invalid_TSS do_invalid_TSS errorentry segment_not_present do_segment_not_present @@ -1601,7 +1666,7 @@ error_sti: */ error_kernelspace: incl %ebx - leaq irq_return(%rip),%rcx + leaq irq_return_iret(%rip),%rcx cmpq %rcx,RIP+8(%rsp) je error_swapgs movl %ecx,%eax /* zero extend */ diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c new file mode 100644 index 000000000000..8a64da36310f --- /dev/null +++ b/arch/x86/kernel/espfix_64.c @@ -0,0 +1,208 @@ +/* ----------------------------------------------------------------------- * + * + * Copyright 2014 Intel Corporation; author: H. Peter Anvin + * + * This program is free software; you can redistribute it and/or modify it + * under the terms and conditions of the GNU General Public License, + * version 2, as published by the Free Software Foundation. + * + * This program is distributed in the hope it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for + * more details. + * + * ----------------------------------------------------------------------- */ + +/* + * The IRET instruction, when returning to a 16-bit segment, only + * restores the bottom 16 bits of the user space stack pointer. This + * causes some 16-bit software to break, but it also leaks kernel state + * to user space. + * + * This works around this by creating percpu "ministacks", each of which + * is mapped 2^16 times 64K apart. When we detect that the return SS is + * on the LDT, we copy the IRET frame to the ministack and use the + * relevant alias to return to userspace. The ministacks are mapped + * readonly, so if the IRET fault we promote #GP to #DF which is an IST + * vector and thus has its own stack; we then do the fixup in the #DF + * handler. + * + * This file sets up the ministacks and the related page tables. The + * actual ministack invocation is in entry_64.S. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* + * Note: we only need 6*8 = 48 bytes for the espfix stack, but round + * it up to a cache line to avoid unnecessary sharing. + */ +#define ESPFIX_STACK_SIZE (8*8UL) +#define ESPFIX_STACKS_PER_PAGE (PAGE_SIZE/ESPFIX_STACK_SIZE) + +/* There is address space for how many espfix pages? */ +#define ESPFIX_PAGE_SPACE (1UL << (PGDIR_SHIFT-PAGE_SHIFT-16)) + +#define ESPFIX_MAX_CPUS (ESPFIX_STACKS_PER_PAGE * ESPFIX_PAGE_SPACE) +#if CONFIG_NR_CPUS > ESPFIX_MAX_CPUS +# error "Need more than one PGD for the ESPFIX hack" +#endif + +#define PGALLOC_GFP (GFP_KERNEL | __GFP_NOTRACK | __GFP_REPEAT | __GFP_ZERO) + +/* This contains the *bottom* address of the espfix stack */ +DEFINE_PER_CPU_READ_MOSTLY(unsigned long, espfix_stack); +DEFINE_PER_CPU_READ_MOSTLY(unsigned long, espfix_waddr); + +/* Initialization mutex - should this be a spinlock? */ +static DEFINE_MUTEX(espfix_init_mutex); + +/* Page allocation bitmap - each page serves ESPFIX_STACKS_PER_PAGE CPUs */ +#define ESPFIX_MAX_PAGES DIV_ROUND_UP(CONFIG_NR_CPUS, ESPFIX_STACKS_PER_PAGE) +static void *espfix_pages[ESPFIX_MAX_PAGES]; + +static __page_aligned_bss pud_t espfix_pud_page[PTRS_PER_PUD] + __aligned(PAGE_SIZE); + +static unsigned int page_random, slot_random; + +/* + * This returns the bottom address of the espfix stack for a specific CPU. + * The math allows for a non-power-of-two ESPFIX_STACK_SIZE, in which case + * we have to account for some amount of padding at the end of each page. + */ +static inline unsigned long espfix_base_addr(unsigned int cpu) +{ + unsigned long page, slot; + unsigned long addr; + + page = (cpu / ESPFIX_STACKS_PER_PAGE) ^ page_random; + slot = (cpu + slot_random) % ESPFIX_STACKS_PER_PAGE; + addr = (page << PAGE_SHIFT) + (slot * ESPFIX_STACK_SIZE); + addr = (addr & 0xffffUL) | ((addr & ~0xffffUL) << 16); + addr += ESPFIX_BASE_ADDR; + return addr; +} + +#define PTE_STRIDE (65536/PAGE_SIZE) +#define ESPFIX_PTE_CLONES (PTRS_PER_PTE/PTE_STRIDE) +#define ESPFIX_PMD_CLONES PTRS_PER_PMD +#define ESPFIX_PUD_CLONES (65536/(ESPFIX_PTE_CLONES*ESPFIX_PMD_CLONES)) + +#define PGTABLE_PROT ((_KERNPG_TABLE & ~_PAGE_RW) | _PAGE_NX) + +static void init_espfix_random(void) +{ + unsigned long rand; + + /* + * This is run before the entropy pools are initialized, + * but this is hopefully better than nothing. + */ + if (!arch_get_random_long(&rand)) { + /* The constant is an arbitrary large prime */ + rdtscll(rand); + rand *= 0xc345c6b72fd16123UL; + } + + slot_random = rand % ESPFIX_STACKS_PER_PAGE; + page_random = (rand / ESPFIX_STACKS_PER_PAGE) + & (ESPFIX_PAGE_SPACE - 1); +} + +void __init init_espfix_bsp(void) +{ + pgd_t *pgd_p; + pteval_t ptemask; + + ptemask = __supported_pte_mask; + + /* Install the espfix pud into the kernel page directory */ + pgd_p = &init_level4_pgt[pgd_index(ESPFIX_BASE_ADDR)]; + pgd_populate(&init_mm, pgd_p, (pud_t *)espfix_pud_page); + + /* Randomize the locations */ + init_espfix_random(); + + /* The rest is the same as for any other processor */ + init_espfix_ap(); +} + +void init_espfix_ap(void) +{ + unsigned int cpu, page; + unsigned long addr; + pud_t pud, *pud_p; + pmd_t pmd, *pmd_p; + pte_t pte, *pte_p; + int n; + void *stack_page; + pteval_t ptemask; + + /* We only have to do this once... */ + if (likely(this_cpu_read(espfix_stack))) + return; /* Already initialized */ + + cpu = smp_processor_id(); + addr = espfix_base_addr(cpu); + page = cpu/ESPFIX_STACKS_PER_PAGE; + + /* Did another CPU already set this up? */ + stack_page = ACCESS_ONCE(espfix_pages[page]); + if (likely(stack_page)) + goto done; + + mutex_lock(&espfix_init_mutex); + + /* Did we race on the lock? */ + stack_page = ACCESS_ONCE(espfix_pages[page]); + if (stack_page) + goto unlock_done; + + ptemask = __supported_pte_mask; + + pud_p = &espfix_pud_page[pud_index(addr)]; + pud = *pud_p; + if (!pud_present(pud)) { + pmd_p = (pmd_t *)__get_free_page(PGALLOC_GFP); + pud = __pud(__pa(pmd_p) | (PGTABLE_PROT & ptemask)); + paravirt_alloc_pud(&init_mm, __pa(pmd_p) >> PAGE_SHIFT); + for (n = 0; n < ESPFIX_PUD_CLONES; n++) + set_pud(&pud_p[n], pud); + } + + pmd_p = pmd_offset(&pud, addr); + pmd = *pmd_p; + if (!pmd_present(pmd)) { + pte_p = (pte_t *)__get_free_page(PGALLOC_GFP); + pmd = __pmd(__pa(pte_p) | (PGTABLE_PROT & ptemask)); + paravirt_alloc_pmd(&init_mm, __pa(pte_p) >> PAGE_SHIFT); + for (n = 0; n < ESPFIX_PMD_CLONES; n++) + set_pmd(&pmd_p[n], pmd); + } + + pte_p = pte_offset_kernel(&pmd, addr); + stack_page = (void *)__get_free_page(GFP_KERNEL); + pte = __pte(__pa(stack_page) | (__PAGE_KERNEL_RO & ptemask)); + paravirt_alloc_pte(&init_mm, __pa(stack_page) >> PAGE_SHIFT); + for (n = 0; n < ESPFIX_PTE_CLONES; n++) + set_pte(&pte_p[n*PTE_STRIDE], pte); + + /* Job is done for this CPU and any CPU which shares this page */ + ACCESS_ONCE(espfix_pages[page]) = stack_page; + +unlock_done: + mutex_unlock(&espfix_init_mutex); +done: + this_cpu_write(espfix_stack, addr); + this_cpu_write(espfix_waddr, (unsigned long)stack_page + + (addr & ~PAGE_MASK)); +} diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c index af1d14a9ebda..ebc987398923 100644 --- a/arch/x86/kernel/ldt.c +++ b/arch/x86/kernel/ldt.c @@ -229,17 +229,6 @@ static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode) } } - /* - * On x86-64 we do not support 16-bit segments due to - * IRET leaking the high bits of the kernel stack address. - */ -#ifdef CONFIG_X86_64 - if (!ldt_info.seg_32bit) { - error = -EINVAL; - goto out_unlock; - } -#endif - fill_ldt(&ldt, &ldt_info); if (oldmode) ldt.avl = 0; diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 34826934d4a7..61a5350850fb 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -243,6 +243,13 @@ static void notrace start_secondary(void *unused) */ check_tsc_sync_target(); + /* + * Enable the espfix hack for this CPU + */ +#ifdef CONFIG_X86_64 + init_espfix_ap(); +#endif + /* * We need to hold vector_lock so there the set of online cpus * does not change while we are assigning vectors to cpus. Holding diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c index 20621d753d5f..167ffcac16ed 100644 --- a/arch/x86/mm/dump_pagetables.c +++ b/arch/x86/mm/dump_pagetables.c @@ -30,12 +30,14 @@ struct pg_state { unsigned long start_address; unsigned long current_address; const struct addr_marker *marker; + unsigned long lines; bool to_dmesg; }; struct addr_marker { unsigned long start_address; const char *name; + unsigned long max_lines; }; /* indices for address_markers; keep sync'd w/ address_markers below */ @@ -46,6 +48,7 @@ enum address_markers_idx { LOW_KERNEL_NR, VMALLOC_START_NR, VMEMMAP_START_NR, + ESPFIX_START_NR, HIGH_KERNEL_NR, MODULES_VADDR_NR, MODULES_END_NR, @@ -68,6 +71,7 @@ static struct addr_marker address_markers[] = { { PAGE_OFFSET, "Low Kernel Mapping" }, { VMALLOC_START, "vmalloc() Area" }, { VMEMMAP_START, "Vmemmap" }, + { ESPFIX_BASE_ADDR, "ESPfix Area", 16 }, { __START_KERNEL_map, "High Kernel Mapping" }, { MODULES_VADDR, "Modules" }, { MODULES_END, "End Modules" }, @@ -182,7 +186,7 @@ static void note_page(struct seq_file *m, struct pg_state *st, pgprot_t new_prot, int level) { pgprotval_t prot, cur; - static const char units[] = "KMGTPE"; + static const char units[] = "BKMGTPE"; /* * If we have a "break" in the series, we need to flush the state that @@ -197,6 +201,7 @@ static void note_page(struct seq_file *m, struct pg_state *st, st->current_prot = new_prot; st->level = level; st->marker = address_markers; + st->lines = 0; pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n", st->marker->name); } else if (prot != cur || level != st->level || @@ -208,17 +213,24 @@ static void note_page(struct seq_file *m, struct pg_state *st, /* * Now print the actual finished series */ - pt_dump_seq_printf(m, st->to_dmesg, "0x%0*lx-0x%0*lx ", - width, st->start_address, - width, st->current_address); + if (!st->marker->max_lines || + st->lines < st->marker->max_lines) { + pt_dump_seq_printf(m, st->to_dmesg, + "0x%0*lx-0x%0*lx ", + width, st->start_address, + width, st->current_address); - delta = (st->current_address - st->start_address) >> 10; - while (!(delta & 1023) && unit[1]) { - delta >>= 10; - unit++; + delta = st->current_address - st->start_address; + while (!(delta & 1023) && unit[1]) { + delta >>= 10; + unit++; + } + pt_dump_cont_printf(m, st->to_dmesg, "%9lu%c ", + delta, *unit); + printk_prot(m, st->current_prot, st->level, + st->to_dmesg); } - pt_dump_cont_printf(m, st->to_dmesg, "%9lu%c ", delta, *unit); - printk_prot(m, st->current_prot, st->level, st->to_dmesg); + st->lines++; /* * We print markers for special areas of address space, @@ -226,7 +238,17 @@ static void note_page(struct seq_file *m, struct pg_state *st, * This helps in the interpretation. */ if (st->current_address >= st->marker[1].start_address) { + if (st->marker->max_lines && + st->lines > st->marker->max_lines) { + unsigned long nskip = + st->lines - st->marker->max_lines; + pt_dump_seq_printf(m, st->to_dmesg, + "... %lu entr%s skipped ... \n", + nskip, + nskip == 1 ? "y" : "ies"); + } st->marker++; + st->lines = 0; pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n", st->marker->name); } diff --git a/init/main.c b/init/main.c index 9c7fd4c9249f..70fc00e7db06 100644 --- a/init/main.c +++ b/init/main.c @@ -616,6 +616,10 @@ asmlinkage void __init start_kernel(void) #ifdef CONFIG_X86 if (efi_enabled(EFI_RUNTIME_SERVICES)) efi_enter_virtual_mode(); +#endif +#ifdef CONFIG_X86_64 + /* Should be run before the first non-init thread is created */ + init_espfix_bsp(); #endif thread_info_cache_init(); cred_init(); From 246f2d2ee1d715e1077fc47d61c394569c8ee692 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Wed, 30 Apr 2014 14:03:25 -0700 Subject: [PATCH 2/7] x86-32, espfix: Remove filter for espfix32 due to race It is not safe to use LAR to filter when to go down the espfix path, because the LDT is per-process (rather than per-thread) and another thread might change the descriptors behind our back. Fortunately it is always *safe* (if a bit slow) to go down the espfix path, and a 32-bit LDT stack segment is extremely rare. Signed-off-by: H. Peter Anvin Link: http://lkml.kernel.org/r/1398816946-3351-1-git-send-email-hpa@linux.intel.com Cc: # consider after upstream merge --- arch/x86/kernel/entry_32.S | 5 ----- 1 file changed, 5 deletions(-) diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S index a2a4f4697889..2780b8f3b96c 100644 --- a/arch/x86/kernel/entry_32.S +++ b/arch/x86/kernel/entry_32.S @@ -551,11 +551,6 @@ ENTRY(iret_exc) CFI_RESTORE_STATE ldt_ss: - larl PT_OLDSS(%esp), %eax - jnz restore_nocheck - testl $0x00400000, %eax # returning to 32bit stack? - jnz restore_nocheck # allright, normal return - #ifdef CONFIG_PARAVIRT /* * The kernel can't run on a non-flat stack if paravirt mode From e1fe9ed8d2a4937510d0d60e20705035c2609aea Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Thu, 1 May 2014 14:12:23 -0700 Subject: [PATCH 3/7] x86, espfix: Move espfix definitions into a separate header file Sparse warns that the percpu variables aren't declared before they are defined. Rather than hacking around it, move espfix definitions into a proper header file. Reported-by: Fengguang Wu Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/espfix.h | 16 ++++++++++++++++ arch/x86/include/asm/setup.h | 5 ++--- arch/x86/kernel/espfix_64.c | 1 + 3 files changed, 19 insertions(+), 3 deletions(-) create mode 100644 arch/x86/include/asm/espfix.h diff --git a/arch/x86/include/asm/espfix.h b/arch/x86/include/asm/espfix.h new file mode 100644 index 000000000000..729051c82b02 --- /dev/null +++ b/arch/x86/include/asm/espfix.h @@ -0,0 +1,16 @@ +#ifdef _ASM_X86_ESPFIX_H +#define _ASM_X86_ESPFIX_H + +#ifdef CONFIG_X86_64 + +#include + +DECLARE_PER_CPU_READ_MOSTLY(unsigned long, espfix_stack); +DECLARE_PER_CPU_READ_MOSTLY(unsigned long, espfix_waddr); + +extern void init_espfix_bsp(void); +extern void init_espfix_ap(void); + +#endif /* CONFIG_X86_64 */ + +#endif /* _ASM_X86_ESPFIX_H */ diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h index 9e3be3329a7e..ff4e7b236e21 100644 --- a/arch/x86/include/asm/setup.h +++ b/arch/x86/include/asm/setup.h @@ -57,11 +57,10 @@ extern void x86_ce4100_early_setup(void); static inline void x86_ce4100_early_setup(void) { } #endif -extern void init_espfix_bsp(void); -extern void init_espfix_ap(void); - #ifndef _SETUP +#include + /* * This is set up by the setup-routine at boot-time */ diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c index 8a64da36310f..6afbb16e9b79 100644 --- a/arch/x86/kernel/espfix_64.c +++ b/arch/x86/kernel/espfix_64.c @@ -40,6 +40,7 @@ #include #include #include +#include /* * Note: we only need 6*8 = 48 bytes for the espfix stack, but round From 20b68535cd27183ebd3651ff313afb2b97dac941 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Fri, 2 May 2014 11:33:51 -0700 Subject: [PATCH 4/7] x86, espfix: Fix broken header guard Header guard is #ifndef, not #ifdef... Reported-by: Fengguang Wu Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/espfix.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/include/asm/espfix.h b/arch/x86/include/asm/espfix.h index 729051c82b02..99efebb2f69d 100644 --- a/arch/x86/include/asm/espfix.h +++ b/arch/x86/include/asm/espfix.h @@ -1,4 +1,4 @@ -#ifdef _ASM_X86_ESPFIX_H +#ifndef _ASM_X86_ESPFIX_H #define _ASM_X86_ESPFIX_H #ifdef CONFIG_X86_64 From 197725de65477bc8509b41388157c1a2283542bb Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Sun, 4 May 2014 10:00:49 -0700 Subject: [PATCH 5/7] x86, espfix: Make espfix64 a Kconfig option, fix UML Make espfix64 a hidden Kconfig option. This fixes the x86-64 UML build which had broken due to the non-existence of init_espfix_bsp() in UML: since UML uses its own Kconfig, this option does not appear in the UML build. This also makes it possible to make support for 16-bit segments a configuration option, for the people who want to minimize the size of the kernel. Reported-by: Ingo Molnar Signed-off-by: H. Peter Anvin Cc: Richard Weinberger Link: http://lkml.kernel.org/r/1398816946-3351-1-git-send-email-hpa@linux.intel.com --- arch/x86/Kconfig | 4 ++++ arch/x86/kernel/Makefile | 2 +- arch/x86/kernel/smpboot.c | 2 +- init/main.c | 2 +- 4 files changed, 7 insertions(+), 3 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 25d2c6f7325e..9a952a572585 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -914,6 +914,10 @@ config VM86 XFree86 to initialize some video cards via BIOS. Disabling this option saves about 6k. +config X86_ESPFIX64 + def_bool y + depends on X86_64 + config TOSHIBA tristate "Toshiba Laptop support" depends on X86_32 diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index 1cc3789d99d9..491ef3e59850 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -29,7 +29,7 @@ obj-$(CONFIG_X86_64) += sys_x86_64.o x8664_ksyms_64.o obj-y += syscall_$(BITS).o vsyscall_gtod.o obj-$(CONFIG_X86_64) += vsyscall_64.o obj-$(CONFIG_X86_64) += vsyscall_emu_64.o -obj-$(CONFIG_X86_64) += espfix_64.o +obj-$(CONFIG_X86_ESPFIX64) += espfix_64.o obj-$(CONFIG_SYSFS) += ksysfs.o obj-y += bootflag.o e820.o obj-y += pci-dma.o quirks.o topology.o kdebugfs.o diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 61a5350850fb..5d93ac1b72db 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -246,7 +246,7 @@ static void notrace start_secondary(void *unused) /* * Enable the espfix hack for this CPU */ -#ifdef CONFIG_X86_64 +#ifdef CONFIG_X86_ESPFIX64 init_espfix_ap(); #endif diff --git a/init/main.c b/init/main.c index 70fc00e7db06..58c132d7de4b 100644 --- a/init/main.c +++ b/init/main.c @@ -617,7 +617,7 @@ asmlinkage void __init start_kernel(void) if (efi_enabled(EFI_RUNTIME_SERVICES)) efi_enter_virtual_mode(); #endif -#ifdef CONFIG_X86_64 +#ifdef CONFIG_X86_ESPFIX64 /* Should be run before the first non-init thread is created */ init_espfix_bsp(); #endif From 34273f41d57ee8d854dcd2a1d754cbb546cb548f Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Sun, 4 May 2014 10:36:22 -0700 Subject: [PATCH 6/7] x86, espfix: Make it possible to disable 16-bit support Embedded systems, which may be very memory-size-sensitive, are extremely unlikely to ever encounter any 16-bit software, so make it a CONFIG_EXPERT option to turn off support for any 16-bit software whatsoever. Signed-off-by: H. Peter Anvin Link: http://lkml.kernel.org/r/1398816946-3351-1-git-send-email-hpa@linux.intel.com --- arch/x86/Kconfig | 23 ++++++++++++++++++----- arch/x86/kernel/entry_32.S | 12 ++++++++++++ arch/x86/kernel/entry_64.S | 8 ++++++++ arch/x86/kernel/ldt.c | 5 +++++ 4 files changed, 43 insertions(+), 5 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 9a952a572585..956c7702471e 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -909,14 +909,27 @@ config VM86 default y depends on X86_32 ---help--- - This option is required by programs like DOSEMU to run 16-bit legacy - code on X86 processors. It also may be needed by software like - XFree86 to initialize some video cards via BIOS. Disabling this - option saves about 6k. + This option is required by programs like DOSEMU to run + 16-bit real mode legacy code on x86 processors. It also may + be needed by software like XFree86 to initialize some video + cards via BIOS. Disabling this option saves about 6K. + +config X86_16BIT + bool "Enable support for 16-bit segments" if EXPERT + default y + ---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_64 + depends on X86_16BIT && X86_64 config TOSHIBA tristate "Toshiba Laptop support" diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S index 2780b8f3b96c..98313ffaae6a 100644 --- a/arch/x86/kernel/entry_32.S +++ b/arch/x86/kernel/entry_32.S @@ -527,6 +527,7 @@ syscall_exit: restore_all: TRACE_IRQS_IRET restore_all_notrace: +#ifdef CONFIG_X86_ESPFIX32 movl PT_EFLAGS(%esp), %eax # mix EFLAGS, SS and CS # Warning: PT_OLDSS(%esp) contains the wrong/random values if we # are returning to the kernel. @@ -537,6 +538,7 @@ restore_all_notrace: cmpl $((SEGMENT_LDT << 8) | USER_RPL), %eax CFI_REMEMBER_STATE je ldt_ss # returning to user-space with LDT SS +#endif restore_nocheck: RESTORE_REGS 4 # skip orig_eax/error_code irq_return: @@ -549,6 +551,7 @@ ENTRY(iret_exc) .previous _ASM_EXTABLE(irq_return,iret_exc) +#ifdef CONFIG_X86_ESPFIX32 CFI_RESTORE_STATE ldt_ss: #ifdef CONFIG_PARAVIRT @@ -592,6 +595,7 @@ ldt_ss: lss (%esp), %esp /* switch to espfix segment */ CFI_ADJUST_CFA_OFFSET -8 jmp restore_nocheck +#endif CFI_ENDPROC ENDPROC(system_call) @@ -699,6 +703,7 @@ END(syscall_badsys) * the high word of the segment base from the GDT and swiches to the * normal stack and adjusts ESP with the matching offset. */ +#ifdef CONFIG_X86_ESPFIX32 /* fixup the stack */ mov GDT_ESPFIX_SS + 4, %al /* bits 16..23 */ mov GDT_ESPFIX_SS + 7, %ah /* bits 24..31 */ @@ -708,8 +713,10 @@ END(syscall_badsys) pushl_cfi %eax lss (%esp), %esp /* switch to the normal stack segment */ CFI_ADJUST_CFA_OFFSET -8 +#endif .endm .macro UNWIND_ESPFIX_STACK +#ifdef CONFIG_X86_ESPFIX32 movl %ss, %eax /* see if on espfix stack */ cmpw $__ESPFIX_SS, %ax @@ -720,6 +727,7 @@ END(syscall_badsys) /* switch to normal stack */ FIXUP_ESPFIX_STACK 27: +#endif .endm /* @@ -1350,11 +1358,13 @@ END(debug) ENTRY(nmi) RING0_INT_FRAME ASM_CLAC +#ifdef CONFIG_X86_ESPFIX32 pushl_cfi %eax movl %ss, %eax cmpw $__ESPFIX_SS, %ax popl_cfi %eax je nmi_espfix_stack +#endif cmpl $ia32_sysenter_target,(%esp) je nmi_stack_fixup pushl_cfi %eax @@ -1394,6 +1404,7 @@ nmi_debug_stack_check: FIX_STACK 24, nmi_stack_correct, 1 jmp nmi_stack_correct +#ifdef CONFIG_X86_ESPFIX32 nmi_espfix_stack: /* We have a RING0_INT_FRAME here. * @@ -1415,6 +1426,7 @@ nmi_espfix_stack: lss 12+4(%esp), %esp # back to espfix stack CFI_ADJUST_CFA_OFFSET -24 jmp irq_return +#endif CFI_ENDPROC END(nmi) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index bffaa986cafc..da0b9bdcc32e 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -1045,8 +1045,10 @@ irq_return: * Are we returning to a stack segment from the LDT? Note: in * 64-bit mode SS:RSP on the exception stack is always valid. */ +#ifdef CONFIG_X86_ESPFIX64 testb $4,(SS-RIP)(%rsp) jnz irq_return_ldt +#endif irq_return_iret: INTERRUPT_RETURN @@ -1058,6 +1060,7 @@ ENTRY(native_iret) _ASM_EXTABLE(native_iret, bad_iret) #endif +#ifdef CONFIG_X86_ESPFIX64 irq_return_ldt: pushq_cfi %rax pushq_cfi %rdi @@ -1081,6 +1084,7 @@ irq_return_ldt: movq %rax,%rsp popq_cfi %rax jmp irq_return_iret +#endif .section .fixup,"ax" bad_iret: @@ -1152,6 +1156,7 @@ END(common_interrupt) * modify the stack to make it look like we just entered * the #GP handler from user space, similar to bad_iret. */ +#ifdef CONFIG_X86_ESPFIX64 ALIGN __do_double_fault: XCPT_FRAME 1 RDI+8 @@ -1177,6 +1182,9 @@ __do_double_fault: retq CFI_ENDPROC END(__do_double_fault) +#else +# define __do_double_fault do_double_fault +#endif /* * End of kprobes section diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c index ebc987398923..c37886d759cc 100644 --- a/arch/x86/kernel/ldt.c +++ b/arch/x86/kernel/ldt.c @@ -229,6 +229,11 @@ static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode) } } + if (!IS_ENABLED(CONFIG_X86_16BIT) && !ldt_info.seg_32bit) { + error = -EINVAL; + goto out_unlock; + } + fill_ldt(&ldt, &ldt_info); if (oldmode) ldt.avl = 0; From 7ed6fb9b5a5510e4ef78ab27419184741169978a Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Wed, 21 May 2014 10:22:59 -0700 Subject: [PATCH 7/7] Revert "x86-64, modify_ldt: Make support for 16-bit segments a runtime option" This reverts commit fa81511bb0bbb2b1aace3695ce869da9762624ff in preparation of merging in the proper fix (espfix64). Signed-off-by: H. Peter Anvin --- arch/x86/kernel/ldt.c | 4 +--- arch/x86/vdso/vdso32-setup.c | 8 -------- 2 files changed, 1 insertion(+), 11 deletions(-) diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c index dcbbaa165bde..af1d14a9ebda 100644 --- a/arch/x86/kernel/ldt.c +++ b/arch/x86/kernel/ldt.c @@ -20,8 +20,6 @@ #include #include -int sysctl_ldt16 = 0; - #ifdef CONFIG_SMP static void flush_ldt(void *current_mm) { @@ -236,7 +234,7 @@ static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode) * IRET leaking the high bits of the kernel stack address. */ #ifdef CONFIG_X86_64 - if (!ldt_info.seg_32bit && !sysctl_ldt16) { + if (!ldt_info.seg_32bit) { error = -EINVAL; goto out_unlock; } diff --git a/arch/x86/vdso/vdso32-setup.c b/arch/x86/vdso/vdso32-setup.c index e1f220e3ca68..00348980a3a6 100644 --- a/arch/x86/vdso/vdso32-setup.c +++ b/arch/x86/vdso/vdso32-setup.c @@ -39,7 +39,6 @@ #ifdef CONFIG_X86_64 #define vdso_enabled sysctl_vsyscall32 #define arch_setup_additional_pages syscall32_setup_pages -extern int sysctl_ldt16; #endif /* @@ -250,13 +249,6 @@ static struct ctl_table abi_table2[] = { .mode = 0644, .proc_handler = proc_dointvec }, - { - .procname = "ldt16", - .data = &sysctl_ldt16, - .maxlen = sizeof(int), - .mode = 0644, - .proc_handler = proc_dointvec - }, {} };