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;
> +}
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