On 10/22/2014 08:09 AM, Namhyung Kim wrote:
Hi Hemant,
On Fri, 10 Oct 2014 16:27:53 +0530, Hemant Kumar wrote:
This patch serves the initial 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.
Signed-off-by: Hemant Kumar <hem...@linux.vnet.ibm.com>
Acked-by: Namhyung Kim <namhy...@kernel.org>
Just a nitpick below..
+static int construct_sdt_notes_list(Elf *elf, struct list_head *sdt_notes)
+{
+ GElf_Ehdr ehdr;
+ Elf_Scn *scn = NULL;
+ Elf_Data *data;
+ GElf_Shdr shdr;
+ size_t shstrndx, next;
+ GElf_Nhdr nhdr;
+ size_t name_off, desc_off, offset;
+ int ret = 0;
+
+ if (gelf_getehdr(elf, &ehdr) == NULL) {
+ ret = -EBADF;
+ goto out_ret;
+ }
+ if (elf_getshdrstrndx(elf, &shstrndx) != 0) {
+ ret = -EBADF;
+ goto out_ret;
+ }
+
+ /* Look for the required section */
+ scn = elf_section_by_name(elf, &ehdr, &shdr, SDT_NOTE_SCN, NULL);
+ if (!scn) {
+ ret = -ENOENT;
+ goto out_ret;
+ }
+
+ if (!(shdr.sh_type == SHT_NOTE) || (shdr.sh_flags & SHF_ALLOC)) {
I think the below is more readable:
Yes.
if ((shdr.sh_type != SHT_NOTE) || (shdr.sh_flags & SHF_ALLOC)) {
Will change to this.
Other than that, looks good to me!
Thanks,
Namhyung
+ ret = -ENOENT;
+ goto out_ret;
+ }
+
+ data = elf_getdata(scn, NULL);
+
+ /* 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,
+ sdt_notes);
+ if (ret < 0)
+ goto out_ret;
+ }
+ }
+ if (list_empty(sdt_notes))
+ ret = -ENOENT;
+
+out_ret:
+ return ret;
+}
--
Thanks,
Hemant Kumar
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