ftrace/x86: Have arch x86_64 use breakpoints instead of stop machine
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>
diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index 268c783..18d9005 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -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 @@
/* No extra data needed for x86 */
};
+int ftrace_int3_handler(struct pt_regs *regs);
+
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* __ASSEMBLY__ */
#endif /* CONFIG_FUNCTION_TRACER */