Messages in this thread Patch in this message | | | Date | Mon, 23 Mar 2015 05:26:49 -0700 | From | tip-bot for Andy Lutomirski <> | Subject | [tip:x86/asm] x86/asm/entry, perf: Explicitly optimize vm86 handling in code_segment_base() |
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Commit-ID: 383f3af3f88aadafe1fcf1948987ad538683fb8c Gitweb: http://git.kernel.org/tip/383f3af3f88aadafe1fcf1948987ad538683fb8c Author: Andy Lutomirski <luto@kernel.org> AuthorDate: Wed, 18 Mar 2015 18:33:30 -0700 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Mon, 23 Mar 2015 11:13:41 +0100
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: 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> --- arch/x86/kernel/cpu/perf_event.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index 979963b..56f7e60 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -2147,18 +2147,19 @@ 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. */ 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) &&
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