Commit-ID: 383f3af3f88aadafe1fcf1948987ad538683fb8c
Gitweb: http://git.kernel.org/tip/383f3af3f88aadafe1fcf1948987ad538683fb8c
Author: Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate: Wed, 18 Mar 2015 18:33:30 -0700
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
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@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brad Spengler <spender@xxxxxxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/dc1457a734feccd03a19bb3538a7648582f57cdd.1426728647.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
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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