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Message-ID: <878uy4ku2b.fsf@sejong.aot.lge.com>
Date: Tue, 08 Oct 2013 18:09:32 +0900
From: Namhyung Kim <namhyung@...nel.org>
To: Hemant Kumar <hkshaw@...ux.vnet.ibm.com>
Cc: linux-kernel@...r.kernel.org, srikar@...ux.vnet.ibm.com,
peterz@...radead.org, oleg@...hat.com,
hegdevasant@...ux.vnet.ibm.com, mingo@...hat.com, anton@...hat.com,
systemtap@...rceware.org, masami.hiramatsu.pt@...achi.com,
aravinda@...ux.vnet.ibm.com
Subject: Re: [PATCH v2 2/3] Support for perf to probe into SDT markers:
On Mon, 07 Oct 2013 12:18:29 +0530, Hemant Kumar wrote:
> This allows perf to probe into the sdt markers/notes present in
> the libraries and executables. We try to find the associated location
> and handle prelinking (since, stapsdt notes section is not allocated
> during runtime). Prelinking is handled with the help of base
> section which is allocated during runtime. This address can be compared
> with the address retrieved from the notes' description. If its different,
> we can take this difference and then add to the note's location.
>
> We can use existing '-a/--add' option to add events for sdt markers.
> Also, we can add multiple events at once using the same '-a' option.
>
> Usage:
> perf probe -x /lib64/libc.so.6 -a 'my_event=%libc:setjmp'
>
> or
>
> perf probe -x /lib64/libc.so.6 %libc:setjmp
>
> Output (corresponding to the first usage):
> Added new event:
> libc:my_event (on 0x35981)
>
> You can now use it in all perf tools, such as:
>
> perf record -e libc:my_event -aR sleep 1
>
>
> Signed-off-by: Hemant Kumar Shaw <hkshaw@...ux.vnet.ibm.com>
> ---
> tools/perf/builtin-probe.c | 11 +++++
> tools/perf/util/probe-event.c | 89 +++++++++++++++++++++++++++++++++++++----
> tools/perf/util/probe-event.h | 2 +
> tools/perf/util/symbol-elf.c | 80 +++++++++++++++++++++++++++++++++++++
> tools/perf/util/symbol.h | 3 +
> 5 files changed, 177 insertions(+), 8 deletions(-)
>
> diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c
> index cbd2383..6f09723 100644
> --- a/tools/perf/builtin-probe.c
> +++ b/tools/perf/builtin-probe.c
> @@ -370,6 +370,17 @@ int cmd_probe(int argc, const char **argv, const char *prefix __maybe_unused)
> pr_err("Error: Don't use --markers with --funcs.\n");
> usage_with_options(probe_usage, options);
> }
> + if (params.mod_events) {
> + ret = add_perf_probe_events(params.events,
> + params.nevents,
> + params.max_probe_points,
> + params.target,
> + params.force_add);
> + if (ret < 0) {
> + pr_err(" Error: Failed to add events. "
> + " (%d)\n", ret);
> + }
> + }
> ret = show_sdt_notes(params.target);
> if (ret < 0) {
> pr_err(" Error : Failed to find SDT markers!"
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index 4e94092..43f8a69 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -817,6 +817,35 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
> arg = tmp;
> }
>
> + /* Check for SDT marker */
> + if (*arg == '%') {
> + ptr = strchr(++arg, ':');
> + if (!ptr) {
> + semantic_error("Provider name must follow an event "
> + "name\n");
> + return -EINVAL;
> + }
> + *ptr++ = '\0';
> + tmp = strdup(arg);
> + if (!tmp)
> + return -ENOMEM;
> +
> + pev->point.note = (struct sdt_note *)
> + zalloc(sizeof(struct sdt_note));
> + if (!pev->point.note)
> + return -ENOMEM;
> + pev->point.note->provider = tmp;
> +
> + tmp = strdup(ptr);
> + if (!tmp)
> + return -ENOMEM;
These -ENOMEM returning should free all memory region allocated
previously.
> + pev->point.note->name = tmp;
> + pev->group = pev->point.note->provider;
> + if (!pev->event)
> + pev->event = pev->point.note->name;
> + pev->sdt = true;
> + return 0;
> + }
> ptr = strpbrk(arg, ";:+@%");
> if (ptr) {
> nc = *ptr;
> @@ -1270,6 +1299,13 @@ static char *synthesize_perf_probe_point(struct perf_probe_point *pp)
> ret = e_snprintf(buf, MAX_CMDLEN, "%s%s%s%s%s", pp->function,
> offs, pp->retprobe ? "%return" : "", line,
> file);
> + else if (pp->note)
> + if (pp->note->bit32)
> + ret = e_snprintf(buf, MAX_CMDLEN, "0x%x",
> + pp->note->addr.a32[0]);
> + else
> + ret = e_snprintf(buf, MAX_CMDLEN, "0x%lx",
> + pp->note->addr.a64[0]);
This kind of code tends to cause 32/64-bit build problem. Did you test
it on a 32-bit system too? Anyway, I think things like below should
work:
unsigned long long addr;
if (pp->note->bit32)
addr = pp->note->addr.a32[0];
else
addr = pp->note->addr.a64[0];
ret = e_snprintf(buf, MAX_CMDLEN, "0x%llx", addr);
> else
> ret = e_snprintf(buf, MAX_CMDLEN, "%s%s", file, line);
> if (ret <= 0)
> @@ -1923,6 +1959,19 @@ static void cleanup_sdt_note_list(struct list_head *sdt_notes)
> }
> }
>
> +static int try_to_find_sdt_notes(struct perf_probe_event *pev,
> + const char *target)
> +{
> + struct list_head sdt_notes;
> + int ret = -1;
> +
> + INIT_LIST_HEAD(&sdt_notes);
You can use just LIST_HEAD(sdt_notes) here.
> + ret = search_sdt_note(pev->point.note, &sdt_notes, target);
> + if (!list_empty(&sdt_notes))
> + cleanup_sdt_note_list(&sdt_notes);
> + return ret;
> +}
> +
> static int convert_to_probe_trace_events(struct perf_probe_event *pev,
> struct probe_trace_event **tevs,
> int max_tevs, const char *target)
> @@ -1930,11 +1979,20 @@ static int convert_to_probe_trace_events(struct perf_probe_event *pev,
> struct symbol *sym;
> int ret = 0, i;
> struct probe_trace_event *tev;
> + char *buf;
>
> - /* Convert perf_probe_event with debuginfo */
> - ret = try_to_find_probe_trace_events(pev, tevs, max_tevs, target);
> - if (ret != 0)
> - return ret; /* Found in debuginfo or got an error */
> + if (pev->sdt) {
> + ret = try_to_find_sdt_notes(pev, target);
> + if (ret)
> + return ret;
> + } else {
> + /* Convert perf_probe_event with debuginfo */
> + ret = try_to_find_probe_trace_events(pev, tevs, max_tevs,
> + target);
> + /* Found in debuginfo or got an error */
> + if (ret != 0)
> + return ret;
> + }
>
> /* Allocate trace event buffer */
> tev = *tevs = zalloc(sizeof(struct probe_trace_event));
> @@ -1942,10 +2000,25 @@ static int convert_to_probe_trace_events(struct perf_probe_event *pev,
> return -ENOMEM;
>
> /* Copy parameters */
> - tev->point.symbol = strdup(pev->point.function);
> - if (tev->point.symbol == NULL) {
> - ret = -ENOMEM;
> - goto error;
> + if (pev->sdt) {
> + buf = (char *)zalloc(sizeof(char) * MAX_CMDLEN);
> + if (!buf) {
> + ret = -ENOMEM;
> + goto error;
> + }
> + if (pev->point.note->bit32)
> + sprintf(buf, "0x%x",
> + (unsigned)pev->point.note->addr.a32[0]);
> + else
> + sprintf(buf, "0x%lx",
> + (unsigned long)pev->point.note->addr.a64[0]);
Please see my comment above.
> + tev->point.symbol = buf;
> + } else {
> + tev->point.symbol = strdup(pev->point.function);
> + if (tev->point.symbol == NULL) {
> + ret = -ENOMEM;
> + goto error;
> + }
> }
>
> if (target) {
> diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
> index b8a9347..4bd50cc 100644
> --- a/tools/perf/util/probe-event.h
> +++ b/tools/perf/util/probe-event.h
> @@ -47,6 +47,7 @@ struct perf_probe_point {
> bool retprobe; /* Return probe flag */
> char *lazy_line; /* Lazy matching pattern */
> unsigned long offset; /* Offset from function entry */
> + struct sdt_note *note;
I guess what you need is a 'struct list_head'.
> };
>
> /* Perf probe probing argument field chain */
> @@ -72,6 +73,7 @@ struct perf_probe_event {
> struct perf_probe_point point; /* Probe point */
> int nargs; /* Number of arguments */
> bool uprobes;
> + bool sdt;
> struct perf_probe_arg *args; /* Arguments */
> };
>
> diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
> index 6b17260..d0e7a66 100644
> --- a/tools/perf/util/symbol-elf.c
> +++ b/tools/perf/util/symbol-elf.c
> @@ -1022,6 +1022,86 @@ out_ret:
> return ret;
> }
>
> +static void adjust_note_addr(struct sdt_note *tmp, struct sdt_note *key,
> + Elf *elf)
> +{
> + GElf_Ehdr ehdr;
> + GElf_Addr base_off = 0;
> + GElf_Shdr shdr;
> +
> + if (!gelf_getehdr(elf, &ehdr)) {
> + pr_debug("%s : cannot get elf header.\n", __func__);
> + return;
> + }
> +
> + /*
> + * Find out the .stapsdt.base section.
> + * This scn will help us to handle prelinking (if present).
> + * Compare the retrieved file offset of the base section with the
> + * base address in the description of the SDT note. If its different,
> + * then accordingly, adjust the note location.
> + */
> + if (elf_section_by_name(elf, &ehdr, &shdr, SDT_BASE, NULL))
> + base_off = shdr.sh_offset;
> + if (base_off) {
> + if (tmp->bit32)
> + key->addr.a32[0] = tmp->addr.a32[0] + base_off -
> + tmp->addr.a32[1];
> + else
> + key->addr.a64[0] = tmp->addr.a64[0] + base_off -
> + tmp->addr.a64[1];
> + }
> + key->bit32 = tmp->bit32;
> +}
> +
> +int search_sdt_note(struct sdt_note *key, struct list_head *sdt_notes,
> + const char *target)
> +{
> + Elf *elf;
> + int fd, ret = -1;
> + struct list_head *pos = NULL, *head = NULL;
> + struct sdt_note *tmp = NULL;
> +
> + fd = open(target, O_RDONLY);
> + if (fd < 0) {
> + pr_err("Failed to open %s\n", target);
> + goto out_ret;
> + }
> +
> + symbol__elf_init();
> + elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
> + if (!elf) {
> + pr_err("%s : can't read %s ELF file.\n", __func__, target);
> + goto out_close;
> + }
> +
> + head = construct_sdt_notes_list(elf);
> + if (!head)
> + goto out_end;
> +
> + list_add(sdt_notes, head);
This list code looks strange.
> +
> + /* Iterate through the notes and retrieve the required note */
> + list_for_each(pos, sdt_notes) {
> + tmp = list_entry(pos, struct sdt_note, note_list);
> + if (!strcmp(key->name, tmp->name) &&
> + !strcmp(key->provider, tmp->provider)) {
> + adjust_note_addr(tmp, key, elf);
> + ret = 0;
> + break;
> + }
> + }
> + if (ret)
> + printf("%%%s:%s not found!\n", key->provider, key->name);
> +
> +out_end:
> + elf_end(elf);
> +out_close:
> + close(fd);
> +out_ret:
> + return ret;
> +}
> +
> void symbol__elf_init(void)
> {
> elf_version(EV_CURRENT);
> diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
> index 037185c..0b0545b 100644
> --- a/tools/perf/util/symbol.h
> +++ b/tools/perf/util/symbol.h
> @@ -260,9 +260,12 @@ void __map_groups__fixup_end(struct map_groups *mg, enum map_type type);
>
> /* Specific to SDT notes */
> int get_sdt_note_list(struct list_head *head, const char *target);
> +int search_sdt_note(struct sdt_note *key, struct list_head *head,
> + const char *target);
>
> #define SDT_NOTE_TYPE 3
> #define NOTE_SCN ".note.stapsdt"
> #define SDT_NOTE_NAME "stapsdt"
> +#define SDT_BASE ".stapsdt.base"
What about SDT_BASE_SCN ?
Thanks,
Namhyung
>
> #endif /* __PERF_SYMBOL */
--
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