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Date: Tue, 6 Jun 2017 13:04:54 +0200
From: Jiri Olsa <jolsa@redhat.com>
To: David Carrillo-Cisneros <davidcc@google.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Andi Kleen <ak@linux.intel.com>, Simon Que <sque@chromium.org>,
        Wang Nan <wangnan0@huawei.com>, Jiri Olsa <jolsa@kernel.org>,
        He Kuang <hekuang@huawei.com>, Masami Hiramatsu <mhiramat@kernel.org>,
        David Ahern <dsa@cumulusnetworks.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Stephane Eranian <eranian@google.com>, Paul Turner <pjt@google.com>
Subject: Re: [PATCH v2 13/13] perf tools: add feature header record to
 pipe-mode
Message-ID: <20170606110454.GB5061@krava>
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 <20170523074853.54892-14-davidcc@google.com>
 <20170525081004.GO14467@krava>
 <CALcN6mgpVerAaNuKic=s=ecCj3JJbz7bnryE0qTHApi0aL1yEQ@mail.gmail.com>
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On Mon, Jun 05, 2017 at 06:32:50PM -0700, David Carrillo-Cisneros wrote:
> On Thu, May 25, 2017 at 1:10 AM, Jiri Olsa <jolsa@redhat.com> wrote:
> > On Tue, May 23, 2017 at 12:48:53AM -0700, David Carrillo-Cisneros wrote:
> >
> > SNIP
> >
> >> +int perf_event__synthesize_features(struct perf_tool *tool,
> >> +                                 struct perf_session *session,
> >> +                                 struct perf_evlist *evlist,
> >> +                                 perf_event__handler_t process)
> >> +{
> >> +     struct perf_header *header = &session->header;
> >> +     struct feat_fd fdd;
> >> +     struct feature_event *fe;
> >> +     size_t sz, sz_hdr;
> >> +     int feat, ret;
> >> +
> >> +     sz_hdr = sizeof(fe->header);
> >> +     sz = sizeof(union perf_event);
> >> +     /* get a nice alignment */
> >> +     sz = PERF_ALIGN(sz, getpagesize());
> >> +
> >> +     memset(&fdd, 0, sizeof(fdd));
> >> +
> >> +     fdd.buf = malloc(sz);
> >> +     if (!fdd.buf)
> >> +             return -ENOMEM;
> >> +
> >> +     fdd.size = sz - sz_hdr;
> >> +
> >> +     for_each_set_bit(feat, header->adds_features, HEADER_FEAT_BITS) {
> >> +             if (!feat_ops[feat].has_record) {
> >> +                     pr_debug("No record header feature for header :%d\n", feat);
> >> +                     continue;
> >> +             }
> >> +
> >> +             fdd.offset = sizeof(*fe);
> >> +
> >> +             ret = feat_ops[feat].write(&fdd, evlist);
> >> +             if (ret || fdd.offset <= (ssize_t)sizeof(*fe)) {
> >> +                     pr_debug("Error writing feature\n");
> >> +                     continue;
> >> +             }
> >> +
> >> +             /* fdd.buf may have changed due to realloc in do_write() */
> >
> > right, so how's ensured the data never cross the maximum event size (0xffff) ?
> >
> > I think do_write should have some check on that
> 
> do_write reallocates ff->buff when it's not large enough.

and what if it's bigger than 0xffff?

jirka