Messages in this thread | | | Date | Tue, 07 Oct 2014 11:39:51 +0530 | From | Hemant Kumar <> | Subject | Re: [PATCH v2 1/5] perf/sdt: ELF support for SDT |
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Hi Namhyung,
On 10/07/2014 07:50 AM, Namhyung Kim wrote: > 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. >
Ok, will pass sdt_notes to populate_sdt_note.
>> + } >> + } >> + 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. :)
Sure.
> Thanks, > Namhyung > > > [...]
-- Thanks, Hemant Kumar
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