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x86_64, traps: Stop using IST for #SS

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On a 32-bit kernel, this has no effect, since there are no IST stacks.

On a 64-bit kernel, #SS can only happen in user code, on a failed iret
to user space, a canonical violation on access via RSP or RBP, or a
genuine stack segment violation in 32-bit kernel code.  The first two
cases don't need IST, and the latter two cases are unlikely fatal bugs,
and promoting them to double faults would be fine.

This fixes a bug in which the espfix64 code mishandles a stack segment
violation.

This saves 4k of memory per CPU and a tiny bit of code.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andy Lutomirski
2014-11-22 18:00:32 -08:00
committed by Linus Torvalds
parent af726f21ed
commit 6f442be2fb
6 changed files with 8 additions and 26 deletions
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arch/x86/include/asm/traps.h
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@@ -39,6 +39,7 @@ asmlinkage void simd_coprocessor_error(void);
#ifdef CONFIG_TRACING
asmlinkage void trace_page_fault(void);
#define trace_stack_segment stack_segment
#define trace_divide_error divide_error
#define trace_bounds bounds
#define trace_invalid_op invalid_op