Messages in this thread | | | From | Namhyung Kim <> | Subject | Re: [PATCH v3 1/5] perf/sdt: ELF support for SDT | Date | Wed, 22 Oct 2014 11:39:48 +0900 |
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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 <hemant@linux.vnet.ibm.com>
Acked-by: Namhyung Kim <namhyung@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:
if ((shdr.sh_type != SHT_NOTE) || (shdr.sh_flags & SHF_ALLOC)) {
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; > +}
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