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x86/asm/entry, perf: Explicitly optimize vm86 handling in code_segment_base()

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There's no point in checking the VM bit on 64-bit, and, since
we're explicitly checking it, we can use user_mode_ignore_vm86()
after the check.

While we're at it, rearrange the #ifdef slightly to make the code
flow a bit clearer.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brad Spengler <spender@grsecurity.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/dc1457a734feccd03a19bb3538a7648582f57cdd.1426728647.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2015-03-18 18:33:30 -07:00 committed by Ingo Molnar
parent a67e7277d0
commit 383f3af3f8
1 changed files with 7 additions and 6 deletions
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13
arch/x86/kernel/cpu/perf_event.c
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@ -2146,6 +2146,12 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
*/ */
static unsigned long code_segment_base(struct pt_regs *regs) static unsigned long code_segment_base(struct pt_regs *regs)
{ {
/*
* For IA32 we look at the GDT/LDT segment base to convert the
* effective IP to a linear address.
*/
#ifdef CONFIG_X86_32
/* /*
* If we are in VM86 mode, add the segment offset to convert to a * If we are in VM86 mode, add the segment offset to convert to a
* linear address. * linear address.
@ -2153,12 +2159,7 @@ static unsigned long code_segment_base(struct pt_regs *regs)
if (regs->flags & X86_VM_MASK) if (regs->flags & X86_VM_MASK)
return 0x10 * regs->cs; return 0x10 * regs->cs;
/* if (user_mode_ignore_vm86(regs) && regs->cs != __USER_CS)
* For IA32 we look at the GDT/LDT segment base to convert the
* effective IP to a linear address.
*/
#ifdef CONFIG_X86_32
if (user_mode(regs) && regs->cs != __USER_CS)
return get_segment_base(regs->cs); return get_segment_base(regs->cs);
#else #else
if (user_mode(regs) && !user_64bit_mode(regs) && if (user_mode(regs) && !user_64bit_mode(regs) &&