linux-kernel - Re: [PATCH -next] tools build: Check return value of fwrite_unlocked in jvmti

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Date:   Thu, 30 Jul 2020 07:03:57 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Wang ShaoBo <bobo.shaobowang@...wei.com>, cj.chengjian@...wei.com,
        Li Bin <huawei.libin@...wei.com>, Jiri Olsa <jolsa@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users <linux-perf-users@...r.kernel.org>
Subject: Re: [PATCH -next] tools build: Check return value of fwrite_unlocked
 in jvmti_agent.c

Em Wed, Jul 29, 2020 at 04:47:36PM -0700, Ian Rogers escreveu:
> On Fri, Jul 24, 2020 at 3:07 AM Wang ShaoBo <bobo.shaobowang@...wei.com> wrote:
> >
> > Function jvmti_write_code called by compiled_method_load_cb may return
> > error in using fwrite_unlocked, this failure should be captured and
> > warned.
> >
> > Signed-off-by: Wang ShaoBo <bobo.shaobowang@...wei.com>
> > ---
> >  tools/perf/jvmti/jvmti_agent.c | 23 +++++++++++++++--------
> >  1 file changed, 15 insertions(+), 8 deletions(-)
> >
> > diff --git a/tools/perf/jvmti/jvmti_agent.c b/tools/perf/jvmti/jvmti_agent.c
> > index 88108598d6e9..a1fe6aa16b6d 100644
> > --- a/tools/perf/jvmti/jvmti_agent.c
> > +++ b/tools/perf/jvmti/jvmti_agent.c
> > @@ -363,7 +363,7 @@ jvmti_write_code(void *agent, char const *sym,
> >         struct jr_code_load rec;
> >         size_t sym_len;
> >         FILE *fp = agent;
> > -       int ret = -1;
> > +       int ret;
> >
> >         /* don't care about 0 length function, no samples */
> >         if (size == 0)
> > @@ -401,16 +401,23 @@ jvmti_write_code(void *agent, char const *sym,
> >         rec.code_index = code_generation++;
> >
> >         ret = fwrite_unlocked(&rec, sizeof(rec), 1, fp);
> > -       fwrite_unlocked(sym, sym_len, 1, fp);
> > +       if (ret)
> > +               goto error;
> 
> Sorry, it seems I lost a reply to this. Won't ret here be the number
> of items written and not an error code? Consequently all writes will
> immediately goto error?

Yeah, I removed it from tmp.perf/core.

Wang, please address Ian review, and consider having just one out exit
label.

- Arnaldo
 
> Thanks,
> Ian
> 
> > +       ret = fwrite_unlocked(sym, sym_len, 1, fp);
> > +       if (ret)
> > +               goto error;
> >
> > -       if (code)
> > -               fwrite_unlocked(code, size, 1, fp);
> > +       if (code) {
> > +               ret = fwrite_unlocked(code, size, 1, fp);
> > +               if (ret)
> > +                       goto error;
> > +       }
> >
> >         funlockfile(fp);
> > -
> > -       ret = 0;
> > -
> > -       return ret;
> > +       return 0;
> > +error:
> > +       funlockfile(fp);
> > +       return -1;
> >  }
> >
> >  int
> > --
> > 2.17.1
> >

-- 

- Arnaldo