On Tue, 26 Sep 2023 00:14:33 +0200
Jiri Olsa [off-list ref] wrote:

On Mon, Sep 25, 2023 at 09:15:15PM +0900, Masami Hiramatsu wrote:

quoted

Hi Jiri,

On Mon, 25 Sep 2023 12:41:59 +0200
Jiri Olsa [off-list ref] wrote:

quoted

On Sun, Sep 24, 2023 at 10:36:36PM +0900, Masami Hiramatsu (Google) wrote:

quoted

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

This allows fprobes to be available with CONFIG_DYNAMIC_FTRACE_WITH_ARGS
instead of CONFIG_DYNAMIC_FTRACE_WITH_REGS, then we can enable fprobe
on arm64.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Florent Revest <redacted>

I was getting bpf selftests failures with this patchset and when
bisecting I'm getting crash when running on top of this change

Thanks for bisecting!

quoted

looks like it's missing some of the regs NULL checks added later?

yeah, if the RIP (arch_rethook_prepare+0x0/0x30) is correct, 

void arch_rethook_prepare(struct rethook_node *rh, struct ftrace_regs *fregs, bool mcount)

RSI (the 2nd argument) is NULL. This means fregs == NULL and caused the crash.
I think ftrace_get_regs(fregs) for the entry handler may return NULL.

Ah, 

@@ -182,7 +182,7 @@ static void fprobe_init(struct fprobe *fp)
 		fp->ops.func = fprobe_kprobe_handler;
 	else
 		fp->ops.func = fprobe_handler;
-	fp->ops.flags |= FTRACE_OPS_FL_SAVE_REGS;
+	fp->ops.flags |= FTRACE_OPS_FL_SAVE_ARGS;
 }
 
 static int fprobe_init_rethook(struct fprobe *fp, int num)

This may cause the issue, it should keep REGS at this point (this must be done in
[9/12]). But after applying [9/12], it shouldn't be a problem... 

Let me check it again.

that helped with the crash, I'll continue bisecting to find out
where it breaks the tests

Can you share the configuration and the test?
I would like to reproduce it because I couldn't make it reproduced.

Thank you,

-- 
Masami Hiramatsu (Google) [off-list ref]