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| author | Andy Lutomirski | 2015-03-07 02:50:19 +0100 |
|---|---|---|
| committer | Ingo Molnar | 2015-03-07 09:34:03 +0100 |
| commit | a7fcf28d431ef70afaa91496e64e16dc51dccec4 (patch) | |
| tree | 3de032435c43db84cdfc4f7e46df4d118b86fe82 /arch/x86/include/asm/processor.h | |
| parent | x86/asm/entry: Delay loading sp0 slightly on task switch (diff) | |
| download | kernel-qcow2-linux-a7fcf28d431ef70afaa91496e64e16dc51dccec4.tar.gz kernel-qcow2-linux-a7fcf28d431ef70afaa91496e64e16dc51dccec4.tar.xz kernel-qcow2-linux-a7fcf28d431ef70afaa91496e64e16dc51dccec4.zip | |
x86/asm/entry: Replace this_cpu_sp0() with current_top_of_stack() and fix it on x86_32
I broke 32-bit kernels. The implementation of sp0 was correct
as far as I can tell, but sp0 was much weirder on x86_32 than I
realized. It has the following issues:
- Init's sp0 is inconsistent with everything else's: non-init tasks
are offset by 8 bytes. (I have no idea why, and the comment is unhelpful.)
- vm86 does crazy things to sp0.
Fix it up by replacing this_cpu_sp0() with
current_top_of_stack() and using a new percpu variable to track
the top of the stack on x86_32.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 75182b1632a8 ("x86/asm/entry: Switch all C consumers of kernel_stack to this_cpu_sp0()")
Link: http://lkml.kernel.org/r/d09dbe270883433776e0cbee3c7079433349e96d.1425692936.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/processor.h')
| -rw-r--r-- | arch/x86/include/asm/processor.h | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index f5e3ec63767d..48a61c1c626e 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -284,6 +284,10 @@ struct tss_struct { DECLARE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss); +#ifdef CONFIG_X86_32 +DECLARE_PER_CPU(unsigned long, cpu_current_top_of_stack); +#endif + /* * Save the original ist values for checking stack pointers during debugging */ @@ -564,9 +568,14 @@ static inline void native_swapgs(void) #endif } -static inline unsigned long this_cpu_sp0(void) +static inline unsigned long current_top_of_stack(void) { +#ifdef CONFIG_X86_64 return this_cpu_read_stable(cpu_tss.x86_tss.sp0); +#else + /* sp0 on x86_32 is special in and around vm86 mode. */ + return this_cpu_read_stable(cpu_current_top_of_stack); +#endif } #ifdef CONFIG_PARAVIRT |