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Message-Id: <20230711090515.3b86f4be7b530200865efd51@kernel.org>
Date: Tue, 11 Jul 2023 09:05:15 +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 v3 4/4] tracing/probes: Fix to record 0-length data_loc
in fetch_store_string*() if fails
On Mon, 10 Jul 2023 18:16:01 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:
> On Sat, 8 Jul 2023 11:48:58 +0900
> "Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:
>
> > --- a/kernel/trace/trace_probe_kernel.h
> > +++ b/kernel/trace/trace_probe_kernel.h
> > @@ -55,8 +55,7 @@ fetch_store_string_user(unsigned long addr, void *dest, void *base)
> > __dest = get_loc_data(dest, base);
> >
> > ret = strncpy_from_user_nofault(__dest, uaddr, maxlen);
> > - if (ret >= 0)
> > - *(u32 *)dest = make_data_loc(ret, __dest - base);
> > + *(u32 *)dest = make_data_loc((ret >= 0) ? ret : 0, __dest - base);
> >
> > return ret;
> > }
> > @@ -87,8 +86,7 @@ fetch_store_string(unsigned long addr, void *dest, void *base)
> > * probing.
> > */
> > ret = strncpy_from_kernel_nofault(__dest, (void *)addr, maxlen);
> > - if (ret >= 0)
> > - *(u32 *)dest = make_data_loc(ret, __dest - base);
> > + *(u32 *)dest = make_data_loc((ret >= 0) ? ret : 0, __dest - base);
>
> The above is a complex line, and not something that I think should be cut
> and pasted between two different locations.
>
> I know you took out the set_data_loc() helper, but really it should have
> stayed, and have used that to update this code in the two places it
> affected, instead of making the changes in those two locations.
>
> That is, patch 3 could have had kept.
>
> static nokprobe_inline void set_data_loc(int ret, void *dest, void *__dest, void *base)
> {
> if (ret >= 0)
> *(u32 *)dest = make_data_loc(ret, __dest - base);
> }
To avoid confusion, I would like to revert the set_data_loc() at the 3rd patch
and add it again in 4th patch.
>
> And this patch could have been:
>
> static nokprobe_inline void set_data_loc(int ret, void *dest, void *__dest, void *base)
> {
> *(u32 *)dest = make_data_loc(ret, __dest - base);
> }
and introduce it. I also want to put the ternary operator into set_data_loc() too
for simplicity.
static nokprobe_inline void set_data_loc(int ret, void *dest, void *__dest, void *base)
{
if (ret < 0)
ret = 0;
*(u32 *)dest = make_data_loc(ret, __dest - base);
}
Thanks,
>
> That would keep the complexity down in this changes set.
>
> -- Steve
>
>
> >
> > return ret;
> > }
--
Masami Hiramatsu (Google) <mhiramat@...nel.org>
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