MIME-Version: 1.0
In-Reply-To: <1440426780-27227-2-git-send-email-alexander.shishkin@linux.intel.com>
References: <1440426780-27227-1-git-send-email-alexander.shishkin@linux.intel.com>
	<1440426780-27227-2-git-send-email-alexander.shishkin@linux.intel.com>
Date: Mon, 31 Aug 2015 21:47:19 +0300
Message-ID: <CAHp75VfEo644UcOr2YWS3usBBOtxGVciaL4j8fjtomk69x=+3g@mail.gmail.com>
Subject: Re: [PATCH v2 1/6] perf: Introduce extended syscall error reporting
From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, Ingo Molnar <mingo@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Arnaldo Carvalho de Melo <acme@infradead.org>,
        Vince Weaver <vince@deater.net>, Stephane Eranian <eranian@google.com>,
        Johannes Berg <johannes@sipsolutions.net>
Content-Type: text/plain; charset=UTF-8
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2389
Lines: 79

On Mon, Aug 24, 2015 at 5:32 PM, Alexander Shishkin
<alexander.shishkin@linux.intel.com> wrote:

One small comment below.

> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -49,6 +49,79 @@
>
>  #include <asm/irq_regs.h>
>
> +static bool extended_reporting_enabled(struct perf_event_attr *attr)
> +{
> +       if (attr->size >= PERF_ATTR_SIZE_VER6 &&
> +           attr->perf_err_size > 0)
> +               return true;
> +
> +       return false;
> +}
> +
> +/*
> + * Provide a JSON formatted error report to the user if they asked for it.
> + */
> +static void perf_error_report_site(struct perf_event_attr *attr,
> +                                  const struct perf_err_site *site)
> +{
> +       unsigned long len;
> +       char *buffer;
> +
> +       if (!site || !extended_reporting_enabled(attr))
> +               return;
> +
> +       /* in case of nested perf_err()s, which you shouldn't really do */
> +       while (site->code <= -PERF_ERRNO)
> +               site = perf_errno_to_site(site->code);
> +
> +       buffer = kasprintf(GFP_KERNEL,
> +                          "{\n"
> +                          "\t\"code\": %d,\n"
> +                          "\t\"module\": \"%s\",\n"
> +                          "\t\"message\": \"%s\"\n"
> +                          "}\n",
> +                          site->code, site->owner, site->message
> +                          );
> +       if (!buffer)
> +               return;
> +
> +       /* trim the buffer to the supplied boundary */
> +       len = strlen(buffer);
> +       if (len >= attr->perf_err_size) {
> +               len = attr->perf_err_size - 1;
> +               buffer[len] = 0;
> +       }

len = strnlen(buffer, attr->perf_err_size);
buffer[len] = 0;

And perhaps perf_err_size has to be length (perf_err_len) ?

> +
> +       if (copy_to_user((void __user *)attr->perf_err, buffer, len + 1)) {
> +               /* if we failed to copy once, don't bother later */
> +               attr->perf_err_size = 0;

Kaboom next time on buffer[-1] = 0; since len >= 0?

> +       }
> +
> +       kfree(buffer);
> +}

-- 
With Best Regards,
Andy Shevchenko
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/