Re: [PATCH] tracing: probes: Fix to zero initialize a local variable
On Wed, 20 Mar 2024 09:27:49 -0400 Steven Rostedt wrote: > On Wed, 20 Mar 2024 17:10:38 +0900 > "Masami Hiramatsu (Google)" wrote: > > > From: Masami Hiramatsu (Google) > > > > Fix to initialize 'val' local variable with zero. > > Dan reported that Smatch static code checker reports an error that a local > > 'val' variable needs to be initialized. Actually, the 'val' is expected to > > be initialized by FETCH_OP_ARG in the same loop, but it is not obvious. So > > initialize it with zero. > > BTW, that loop should really have a comment stating that FETCH_OP_ARG is > expected to happen before FETCH_OP_ST_EDATA. Indeed, OK, let me add it. Thank you, > > -- Steve -- Masami Hiramatsu (Google)
Re: [PATCH] tracing: probes: Fix to zero initialize a local variable
On Wed, 20 Mar 2024 17:10:38 +0900 "Masami Hiramatsu (Google)" wrote: > From: Masami Hiramatsu (Google) > > Fix to initialize 'val' local variable with zero. > Dan reported that Smatch static code checker reports an error that a local > 'val' variable needs to be initialized. Actually, the 'val' is expected to > be initialized by FETCH_OP_ARG in the same loop, but it is not obvious. So > initialize it with zero. BTW, that loop should really have a comment stating that FETCH_OP_ARG is expected to happen before FETCH_OP_ST_EDATA. -- Steve
Re: [PATCH] tracing: probes: Fix to zero initialize a local variable
On Wed, 20 Mar 2024 17:10:38 +0900 "Masami Hiramatsu (Google)" wrote: > From: Masami Hiramatsu (Google) > > Fix to initialize 'val' local variable with zero. > Dan reported that Smatch static code checker reports an error that a local > 'val' variable needs to be initialized. Actually, the 'val' is expected to > be initialized by FETCH_OP_ARG in the same loop, but it is not obvious. So > initialize it with zero. > > Reported-by: Dan Carpenter > Closes: > https://lore.kernel.org/all/b010488e-68aa-407c-add0-3e059254aaa0@moroto.mountain/ > Fixes: 25f00e40ce79 ("tracing/probes: Support $argN in return probe (kprobe > and fprobe)") > Signed-off-by: Masami Hiramatsu (Google) > --- Reviewed-by: Steven Rostedt (Google) -- Steve > kernel/trace/trace_probe.c |2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c > index 217169de0920..dfe3ee6035ec 100644 > --- a/kernel/trace/trace_probe.c > +++ b/kernel/trace/trace_probe.c > @@ -839,7 +839,7 @@ int traceprobe_get_entry_data_size(struct trace_probe *tp) > void store_trace_entry_data(void *edata, struct trace_probe *tp, struct > pt_regs *regs) > { > struct probe_entry_arg *earg = tp->entry_arg; > - unsigned long val; > + unsigned long val = 0; > int i; > > if (!earg)
Re: [bug report] tracing/probes: Support $argN in return probe (kprobe and fprobe)
On Wed, 20 Mar 2024 12:44:23 +0900 Masami Hiramatsu (Google) wrote: > > > kernel/trace/trace_probe.c > > > 846 return; > > > 847 > > > 848 for (i = 0; i < earg->size; i++) { > > > 849 struct fetch_insn *code = >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
[PATCH] tracing: probes: Fix to zero initialize a local variable
From: Masami Hiramatsu (Google) Fix to initialize 'val' local variable with zero. Dan reported that Smatch static code checker reports an error that a local 'val' variable needs to be initialized. Actually, the 'val' is expected to be initialized by FETCH_OP_ARG in the same loop, but it is not obvious. So initialize it with zero. Reported-by: Dan Carpenter Closes: https://lore.kernel.org/all/b010488e-68aa-407c-add0-3e059254aaa0@moroto.mountain/ Fixes: 25f00e40ce79 ("tracing/probes: Support $argN in return probe (kprobe and fprobe)") Signed-off-by: Masami Hiramatsu (Google) --- kernel/trace/trace_probe.c |2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index 217169de0920..dfe3ee6035ec 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -839,7 +839,7 @@ int traceprobe_get_entry_data_size(struct trace_probe *tp) void store_trace_entry_data(void *edata, struct trace_probe *tp, struct pt_regs *regs) { struct probe_entry_arg *earg = tp->entry_arg; - unsigned long val; + unsigned long val = 0; int i; if (!earg)