ftrace: use dynamic patching for updating mcount calls

Browse source

This patch replaces the indirect call to the mcount function
pointer with a direct call that will be patched by the
dynamic ftrace routines.

On boot up, the mcount function calls the ftace_stub function.
When the dynamic ftrace code is initialized, the ftrace_stub
is replaced with a call to the ftrace_record_ip, which records
the instruction pointers of the locations that call it.

Later, the ftraced daemon will call kstop_machine and patch all
the locations to nops.

When a ftrace is enabled, the original calls to mcount will now
be set top call ftrace_caller, which will do a direct call
to the registered ftrace function. This direct call is also patched
when the function that should be called is updated.

All patching is performed by a kstop_machine routine to prevent any
type of race conditions that is associated with modifying code
on the fly.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

...

This commit is contained in:

Steven Rostedt 2008-05-12 21:20:43 +02:00 • committed by Thomas Gleixner

parent 3c1720f00b

commit d61f82d066

5 changed files with 261 additions and 84 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

47

arch/x86/kernel/entry_32.S

View file

67

arch/x86/kernel/entry_64.S

View file

41

arch/x86/kernel/ftrace.c

View file

7

include/linux/ftrace.h

View file

185

kernel/trace/ftrace.c

View file