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Message-Id: <20230706134036.5c074aa5fc6a55cdb5038660@kernel.org>
Date: Thu, 6 Jul 2023 13:40:36 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Dan Carpenter <dan.carpenter@...aro.org>,
linux-trace-kernel@...r.kernel.org,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] tracing/probes: Fix return value when "(fault)" is
injected
On Wed, 5 Jul 2023 22:49:56 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:
> On Sun, 2 Jul 2023 23:47:35 +0900
> "Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:
>
> > From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> >
> > When the "(fault)" is injected, the return value of fetch_store_string*()
> > should be the length of the "(fault)", but an error code is returned.
> > Fix it to return the correct length and update the data_loc according the
> > updated length.
> > This needs to update a ftracetest test case, which expects trace output
> > to appear as '(fault)' instead of '"(fault)"'.
> >
>
> Ah, because of patch 2, the ret < 0 makes it return without printing the
> "fault"?
No, actually set_data_loc() updates the 'ret' argument, but it is just
disposed... (not returned to the caller)
-static nokprobe_inline void set_data_loc(int ret, void *dest, void *__dest, void *base, int len)
+static nokprobe_inline int set_data_loc(int ret, void *dest, void *__dest, void *base, int len)
{
- if (ret >= 0) {
- *(u32 *)dest = make_data_loc(ret, __dest - base);
- } else {
+ if (ret < 0) {
strscpy(__dest, FAULT_STRING, len);
ret = strlen(__dest) + 1;
}
+
+ *(u32 *)dest = make_data_loc(ret, __dest - base);
+ return ret;
}
So this returns updated 'ret', and also update data_loc to use the
updated 'ret' value (which is the length of the stored data).
>
> Reviewed-by: Steven Rostedt (Google) <rostedt@...dmis.org>
Thank you!
>
> -- Steve
>
>
> > Fixes: 2e9906f84fc7 ("tracing: Add "(fault)" name injection to kernel probes")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > ---
--
Masami Hiramatsu (Google) <mhiramat@...nel.org>
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