From: Steven Rostedt <rostedt@goodmis.org>
To: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Dan Carpenter <dan.carpenter@linaro.org>,
linux-trace-kernel@vger.kernel.org
Subject: Re: [bug report] tracing/probes: Support $argN in return probe (kprobe and fprobe)
Date: Wed, 20 Mar 2024 09:22:53 -0400 [thread overview]
Message-ID: <20240320092253.2423ec30@gandalf.local.home> (raw)
In-Reply-To: <20240320124423.54cdb56dc8a07378fd09de38@kernel.org>
On Wed, 20 Mar 2024 12:44:23 +0900
Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:
> > > kernel/trace/trace_probe.c
> > > 846 return;
> > > 847
> > > 848 for (i = 0; i < earg->size; i++) {
> > > 849 struct fetch_insn *code = &earg->code[i];
> > > 850
> > > 851 switch (code->op) {
> > > 852 case FETCH_OP_ARG:
> > > 853 val = regs_get_kernel_argument(regs, code->param);
> > > 854 break;
> > > 855 case FETCH_OP_ST_EDATA:
> > > --> 856 *(unsigned long *)((unsigned long)edata + code->offset) = val;
> > >
> > > Probably the earg->code[i] always has FETCH_OP_ARG before
> > > FETCH_OP_ST_EDATA but Smatch isn't smart enough to figure that out...
> >
> > Looks that way:
> >
> > case FETCH_OP_END:
> > earg->code[i].op = FETCH_OP_ARG;
> > earg->code[i].param = argnum;
> > earg->code[i + 1].op = FETCH_OP_ST_EDATA;
> > earg->code[i + 1].offset = offset;
> > return offset;
> >
> > But probably should still initialize val to zero or have a WARN_ON() if
> > that doesn't happen.
>
> OK, let's val = 0 in the store_trace_entry_data(), but WARN_ON() in this loop
> is a bit strange. I think we should have a verifiler.
Initializing to zero is fine.
-- Steve
next prev parent reply other threads:[~2024-03-20 13:20 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-19 7:19 [bug report] tracing/probes: Support $argN in return probe (kprobe and fprobe) Dan Carpenter
2024-03-19 14:10 ` Steven Rostedt
2024-03-19 14:39 ` Dan Carpenter
2024-03-20 3:44 ` Masami Hiramatsu
2024-03-20 13:22 ` Steven Rostedt [this message]
2024-03-20 8:10 ` [PATCH] tracing: probes: Fix to zero initialize a local variable Masami Hiramatsu (Google)
2024-03-20 13:26 ` Steven Rostedt
2024-03-20 13:27 ` Steven Rostedt
2024-03-20 22:56 ` Masami Hiramatsu
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