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| author | Tejun Heo <tj@kernel.org> | 2009-02-09 16:17:40 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-02-10 02:42:01 +0300 |
| commit | 60a5317ff0f42dd313094b88f809f63041568b08 (patch) | |
| tree | 307dfd9715fbc9ff83c3c3ae3b0e8f03888083f2 /arch/x86/include/asm/system.h | |
| parent | ccbeed3a05908d201b47b6c3dd1a373138bba566 (diff) | |
| download | linux-60a5317ff0f42dd313094b88f809f63041568b08.tar.xz | |
x86: implement x86_32 stack protector
Impact: stack protector for x86_32
Implement stack protector for x86_32. GDT entry 28 is used for it.
It's set to point to stack_canary-20 and have the length of 24 bytes.
CONFIG_CC_STACKPROTECTOR turns off CONFIG_X86_32_LAZY_GS and sets %gs
to the stack canary segment on entry. As %gs is otherwise unused by
the kernel, the canary can be anywhere. It's defined as a percpu
variable.
x86_32 exception handlers take register frame on stack directly as
struct pt_regs. With -fstack-protector turned on, gcc copies the
whole structure after the stack canary and (of course) doesn't copy
back on return thus losing all changed. For now, -fno-stack-protector
is added to all files which contain those functions. We definitely
need something better.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/include/asm/system.h')
| -rw-r--r-- | arch/x86/include/asm/system.h | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h index 79b98e5b96f4..2692ee8ef031 100644 --- a/arch/x86/include/asm/system.h +++ b/arch/x86/include/asm/system.h @@ -23,6 +23,22 @@ struct task_struct *__switch_to(struct task_struct *prev, #ifdef CONFIG_X86_32 +#ifdef CONFIG_CC_STACKPROTECTOR +#define __switch_canary \ + "movl "__percpu_arg([current_task])",%%ebx\n\t" \ + "movl %P[task_canary](%%ebx),%%ebx\n\t" \ + "movl %%ebx,"__percpu_arg([stack_canary])"\n\t" +#define __switch_canary_oparam \ + , [stack_canary] "=m" (per_cpu_var(stack_canary)) +#define __switch_canary_iparam \ + , [current_task] "m" (per_cpu_var(current_task)) \ + , [task_canary] "i" (offsetof(struct task_struct, stack_canary)) +#else /* CC_STACKPROTECTOR */ +#define __switch_canary +#define __switch_canary_oparam +#define __switch_canary_iparam +#endif /* CC_STACKPROTECTOR */ + /* * Saving eflags is important. It switches not only IOPL between tasks, * it also protects other tasks from NT leaking through sysenter etc. @@ -46,6 +62,7 @@ do { \ "pushl %[next_ip]\n\t" /* restore EIP */ \ "jmp __switch_to\n" /* regparm call */ \ "1:\t" \ + __switch_canary \ "popl %%ebp\n\t" /* restore EBP */ \ "popfl\n" /* restore flags */ \ \ @@ -58,6 +75,8 @@ do { \ "=b" (ebx), "=c" (ecx), "=d" (edx), \ "=S" (esi), "=D" (edi) \ \ + __switch_canary_oparam \ + \ /* input parameters: */ \ : [next_sp] "m" (next->thread.sp), \ [next_ip] "m" (next->thread.ip), \ @@ -66,6 +85,8 @@ do { \ [prev] "a" (prev), \ [next] "d" (next) \ \ + __switch_canary_iparam \ + \ : /* reloaded segment registers */ \ "memory"); \ } while (0) |