Re: [PATCH v3 5/6] x86/ftrace: Use text_poke()

From: Peter Zijlstra
Date: Thu Oct 10 2019 - 05:21:13 EST

On Wed, Oct 09, 2019 at 10:41:35PM -0400, Steven Rostedt wrote:
> On Tue, 8 Oct 2019 10:43:35 -0400
> Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> > BTW, I'd really like to take this patch series through my tree. That
> > way I can really hammer it, as well as I have code that will be built
> > on top of it.
> I did a bit of hammering and found two bugs. One I sent a patch to fix
> (adding a module when tracing is enabled), but the other bug I
> triggered, I'm too tired to debug right now. But figured I'd mention it
> anyway.

I'm thinking this should fix it... Just not sure this is the right plce,
then again, we're doing the same thing in jump_label and static_call, so
perhaps we should do it like this.

--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -1230,10 +1230,15 @@ void text_poke_queue(void *addr, const v
* dynamically allocated memory. This function should be used when it is
* not possible to allocate memory.
-void text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate)
+void __ref text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate)
struct text_poke_loc tp;

+ if (unlikely(system_state == SYSTEM_BOOTING)) {
+ text_poke_early(addr, opcode, len);
+ return;
+ }
text_poke_loc_init(&tp, addr, opcode, len, emulate);
text_poke_bp_batch(&tp, 1);