On Fri, May 14, 2021 at 7:10 AM Florent Revest <revest@xxxxxxxxxxxx> wrote:
>
> On Fri, May 14, 2021 at 8:37 AM kernel test robot <lkp@xxxxxxxxx> wrote:
> > cppcheck possible warnings: (new ones prefixed by >>, may not real problems)
> >
> > >> kernel/bpf/helpers.c:713:43: warning: Uninitialized variable: bufs [uninitvar]
> > if (WARN_ON_ONCE(nest_level > ARRAY_SIZE(bufs->tmp_bufs))) {
> > ^
>
> I don't think this is a real problem. bufs is not actually
> dereferenced, it is only used to give the type information to a
> sizeof. This is only evaluated at compilation time.
>
> If this matters, I guess we could silent this cppcheck warning with
> something like the following patch. Alexei, what do you think ?
>
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -697,8 +697,9 @@ static int bpf_trace_copy_string(char *buf, void
> *unsafe_ptr, char fmt_ptype,
> #define MAX_PRINTF_BUF_LEN 512
>
> /* Support executing three nested bprintf helper calls on a given CPU */
> +#define MAX_PRINTF_NEST_LEVEL 3
> struct bpf_bprintf_buffers {
> - char tmp_bufs[3][MAX_PRINTF_BUF_LEN];
> + char tmp_bufs[MAX_PRINTF_NEST_LEVEL][MAX_PRINTF_BUF_LEN];
> };
> static DEFINE_PER_CPU(struct bpf_bprintf_buffers, bpf_bprintf_bufs);
> static DEFINE_PER_CPU(int, bpf_bprintf_nest_level);
> @@ -710,7 +711,7 @@ static int try_get_fmt_tmp_buf(char **tmp_buf)
>
> preempt_disable();
> nest_level = this_cpu_inc_return(bpf_bprintf_nest_level);
> - if (WARN_ON_ONCE(nest_level > ARRAY_SIZE(bufs->tmp_bufs))) {
> + if (WARN_ON_ONCE(nest_level > MAX_PRINTF_NEST_LEVEL)) {
Yeah. Why not. I think it's cleaner overall.
