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Commit 383f3af3 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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x86/asm/entry, perf: Explicitly optimize vm86 handling in code_segment_base() 



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: default avatarAndy 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: default avatarIngo Molnar <mingo@kernel.org>
parent a67e7277

arch/x86/kernel/cpu/perf_event.c

+7 −6
Original line number Diff line number Diff line
@@ -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)

{

	/*

	 * 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

	 * linear address.
@@ -2153,12 +2159,7 @@ static unsigned long code_segment_base(struct pt_regs *regs) 
	if (regs->flags & X86_VM_MASK)

		return 0x10 * regs->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)

	if (user_mode_ignore_vm86(regs) && regs->cs != __USER_CS)

		return get_segment_base(regs->cs);

#else

	if (user_mode(regs) && !user_64bit_mode(regs) &&