Messages in this thread |  | | Date | Wed, 22 Oct 2014 15:56:31 +0530 | From | Hemant Kumar <> | Subject | Re: [PATCH v3 1/5] perf/sdt: ELF support for SDT |
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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 <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:
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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