From: Namhyung Kim <namhyung@kernel.org>
To: Hemant Kumar <hemant@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, srikar@linux.vnet.ibm.com,
peterz@infradead.org, oleg@redhat.com,
hegdevasant@linux.vnet.ibm.com, mingo@redhat.com,
anton@redhat.com, systemtap@sourceware.org,
masami.hiramatsu.pt@hitachi.com, aravinda@linux.vnet.ibm.com,
penberg@iki.fi
Subject: Re: [PATCH v2 1/5] perf/sdt: ELF support for SDT
Date: Tue, 07 Oct 2014 02:20:00 -0000 [thread overview]
Message-ID: <87mw98hb8v.fsf@sejong.aot.lge.com> (raw)
In-Reply-To: <20141001024525.28985.95513.stgit@hemant-fedora> (Hemant Kumar's message of "Wed, 01 Oct 2014 08:17:24 +0530")
Hi Hemant,
On Wed, 01 Oct 2014 08:17:24 +0530, Hemant Kumar wrote:
> This patch serves as the basic support to identify and list SDT events in binaries.
> When programs containing SDT markers are compiled, gcc with the help of assembler
> directives identifies them and places them in the section ".note.stapsdt". To find
> these markers from the binaries, one needs to traverse through this section and
> parse the relevant details like the name, type and location of the marker. Also,
> the original location could be skewed due to the effect of prelinking. If that is
> the case, the locations need to be adjusted.
>
> The functions in this patch open a given ELF, find out the SDT section, parse the
> relevant details, adjust the location (if necessary) and populate them in a list.
>
> Made the necessary changes as suggested by Namhyung Kim.
Below are just few more nitpicks, other than that, looks good to me.
[SNIP]
> + /* Get the SDT notes */
> + for (offset = 0; (next = gelf_getnote(data, offset, &nhdr, &name_off,
> + &desc_off)) > 0; offset = next) {
> + if (nhdr.n_namesz == sizeof(SDT_NOTE_NAME) &&
> + !memcmp(data->d_buf + name_off, SDT_NOTE_NAME,
> + sizeof(SDT_NOTE_NAME))) {
> + ret = populate_sdt_note(&elf, ((data->d_buf) + desc_off),
> + nhdr.n_descsz, nhdr.n_type,
> + &tmp);
> + if (ret < 0)
> + goto out_ret;
> + list_add_tail(&tmp->note_list, sdt_notes);
I think we can just pass the sdt_notes list into populate_sdt_note()
instead of passing a tmp pointer.
> + }
> + }
> + if (list_empty(sdt_notes))
> + ret = -ENOENT;
> +
> +out_ret:
> + return ret;
> +}
> +
> +/*
> + * get_sdt_note_list() : Takes two arguments "head" and "target", where head
> + * is the head of the SDT events' list and "target" is the file name as to
> + * where the SDT events should be looked for. This opens the file, initializes
> + * the ELF and then calls construct_sdt_notes_list.
> + */
> +int get_sdt_note_list(struct list_head *head, const char *target)
> +{
> + Elf *elf;
> + int fd, ret;
> +
> + fd = open(target, O_RDONLY);
> + if (fd < 0)
> + return -EBADF;
> +
> + elf = elf_begin(fd, ELF_C_READ, NULL);
You may want to use PERF_ELF_C_READ_MMAP. :)
Thanks,
Namhyung
> + if (!elf) {
> + ret = -EBADF;
> + goto out_close;
> + }
> + ret = construct_sdt_notes_list(elf, head);
> + elf_end(elf);
> +out_close:
> + close(fd);
> + return ret;
> +}
next prev parent reply other threads:[~2014-10-07 2:20 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-01 17:37 [PATCH v2 0/5] perf/sdt: SDT events listing/probing Hemant Kumar
2014-10-01 17:38 ` [PATCH v2 1/5] perf/sdt: ELF support for SDT Hemant Kumar
2014-10-03 11:39 ` Masami Hiramatsu
2014-10-05 8:17 ` Hemant Kumar
2014-10-07 2:20 ` Namhyung Kim [this message]
2014-10-07 6:10 ` Hemant Kumar
2014-10-01 17:39 ` [PATCH v2 3/5] perf/sdt: Show SDT cache contents Hemant Kumar
2014-10-03 12:52 ` Masami Hiramatsu
2014-10-03 12:55 ` Masami Hiramatsu
2014-10-05 8:18 ` Hemant Kumar
2014-10-01 17:40 ` [PATCH v2 2/5] perf/sdt: Add SDT events into a cache Hemant Kumar
2014-10-07 3:00 ` Namhyung Kim
2014-10-07 6:23 ` Hemant Kumar
2014-10-01 17:40 ` [PATCH v2 5/5] perf/sdt: Add support to perf record to trace SDT events Hemant Kumar
2014-10-01 17:40 ` [PATCH v2 4/5] perf/sdt: Delete SDT events from cache Hemant Kumar
2014-10-07 3:17 ` Namhyung Kim
2014-10-07 6:25 ` Hemant Kumar
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