diff options
author | Andi Kleen <ak@suse.de> | 2006-09-26 08:52:28 (GMT) |
---|---|---|
committer | Andi Kleen <andi@basil.nowhere.org> | 2006-09-26 08:52:28 (GMT) |
commit | 31679f38d88696ed032d59e457f1605c97e7d719 (patch) | |
tree | 901c0e9a3ce8696a1c0560c53edde36a85db9aa6 /arch/x86_64/kernel | |
parent | 0cb91a2293648507886563ccb91979cfc94d6a4b (diff) | |
download | linux-31679f38d88696ed032d59e457f1605c97e7d719.tar.xz |
[PATCH] Simplify profile_pc on x86-64
Use knowledge about EFLAGS layout (bits 22:63 are always 0) to distingush
EFLAGS word and kernel address in the spin lock stack frame.
Signed-off-by: Andi Kleen <ak@suse.de>
Diffstat (limited to 'arch/x86_64/kernel')
-rw-r--r-- | arch/x86_64/kernel/time.c | 21 |
1 files changed, 8 insertions, 13 deletions
diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c index 560ed94..ea00915 100644 --- a/arch/x86_64/kernel/time.c +++ b/arch/x86_64/kernel/time.c @@ -189,20 +189,15 @@ unsigned long profile_pc(struct pt_regs *regs) { unsigned long pc = instruction_pointer(regs); - /* Assume the lock function has either no stack frame or only a single - word. This checks if the address on the stack looks like a kernel - text address. - There is a small window for false hits, but in that case the tick - is just accounted to the spinlock function. - Better would be to write these functions in assembler again - and check exactly. */ + /* Assume the lock function has either no stack frame or a copy + of eflags from PUSHF + Eflags always has bits 22 and up cleared unlike kernel addresses. */ if (!user_mode(regs) && in_lock_functions(pc)) { - char *v = *(char **)regs->rsp; - if ((v >= _stext && v <= _etext) || - (v >= _sinittext && v <= _einittext) || - (v >= (char *)MODULES_VADDR && v <= (char *)MODULES_END)) - return (unsigned long)v; - return ((unsigned long *)regs->rsp)[1]; + unsigned long *sp = (unsigned long *)regs->rsp; + if (sp[0] >> 22) + return sp[0]; + if (sp[1] >> 22) + return sp[1]; } return pc; } |