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ftrace/x86: Have arch x86_64 use breakpoints instead of stop machine

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This method changes x86 to add a breakpoint to the mcount locations
instead of calling stop machine.

Now that iret can be handled by NMIs, we perform the following to
update code:

1) Add a breakpoint to all locations that will be modified

2) Sync all cores

3) Update all locations to be either a nop or call (except breakpoint
   op)

4) Sync all cores

5) Remove the breakpoint with the new code.

6) Sync all cores

[
  Added updates that Masami suggested:
   Use unlikely(modifying_ftrace_code) in int3 trap to keep kprobes efficient.
   Don't use NOTIFY_* in ftrace handler in int3 as it is not a notifier.
]

Cc: H. Peter Anvin <hpa@zytor.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt 2011-08-16 09:57:10 -04:00 • committed by Steven Rostedt
parent 438ced1720
commit 08d636b6d4
4 changed files with 358 additions and 1 deletions
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3
arch/x86/include/asm/ftrace.h
View file

@ -34,6 +34,7 @@
#ifndef __ASSEMBLY__
extern void mcount(void);
extern int modifying_ftrace_code;
static inline unsigned long ftrace_call_adjust(unsigned long addr)
{
@ -50,6 +51,8 @@ struct dyn_arch_ftrace {
/* No extra data needed for x86 */
};
int ftrace_int3_handler(struct pt_regs *regs);
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* __ASSEMBLY__ */
#endif /* CONFIG_FUNCTION_TRACER */