Le 19/04/2017 à 16:01, Michael Ellerman a écrit :

Christophe Leroy [off-list ref] writes:

quoted

diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index 32509de6ce4c..4af81fb23653 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c

@@ -526,7 +526,9 @@ void ftrace_replace_code(int enable)
  */
 void arch_ftrace_update_code(int command)
 {
+	set_kernel_text_rw();
 	ftrace_modify_all_code(command);
+	set_kernel_text_ro();
 }

I'm not sure that's the right place for that.

I took arch/arm/ as model. It does the following. Is that wrong ?


static int __ftrace_modify_code(void *data)
{
	int *command = data;

	set_kernel_text_rw();
	ftrace_modify_all_code(*command);
	set_kernel_text_ro();

	return 0;
}

void arch_ftrace_update_code(int command)
{
	stop_machine(__ftrace_modify_code, &command, NULL);
}

If you look at other arches they hook into ftrace_modify_code(), where
you have the address that's being modified.

Ok, I will look at other arches.

Christophe