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

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Date:   Fri, 31 Jul 2020 19:58:58 +0800
From:   "Wangshaobo (bobo)" <bobo.shaobowang@...wei.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ian Rogers <irogers@...gle.com>
CC:     <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


在 2020/7/30 18:03, Arnaldo Carvalho de Melo 写道:
> 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
>   

I am sorry I forgot what does fwrite_unlocked return, as same as fwrite 
error happens,

the return val is a short item count (or zero)  but not equals the items 
written. I have fixed

it and already sent v2 and address Ian review, thanks a lot.

... and i refer to the writing of function jvmti_write_debug_info() for 
giving out exit label,

thanks again,

- Wang ShaoBo

>> 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
>>>