Le 19/04/2017 à 16:22, Christophe LEROY a écrit :
Le 19/04/2017 à 16:01, Michael Ellerman a écrit :
Christophe Leroy <christophe.le...@c-s.fr> writes:
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.
Could you provide more details on what you have seen on other arches ? I
didn't notice anything related in any other arches' ftrace_modify_code()
What I could find however is, in x86, the use of
ftrace_arch_code_modify_prepare() and
ftrace_arch_code_modify_post_process ():
int ftrace_arch_code_modify_prepare(void)
{
set_kernel_text_rw();
set_all_modules_text_rw();
return 0;
}
int ftrace_arch_code_modify_post_process(void)
{
set_all_modules_text_ro();
set_kernel_text_ro();
return 0;
}
Those functions are also used on arm but only for modules:
int ftrace_arch_code_modify_prepare(void)
{
set_all_modules_text_rw();
return 0;
}
int ftrace_arch_code_modify_post_process(void)
{
set_all_modules_text_ro();
/* Make sure any TLB misses during machine stop are cleared. */
flush_tlb_all();
return 0;
}
Should I apply the x86 approach, or something else ?
Christophe
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