Re: [PATCH v9 4/4] perf probe: Support SDT markers having reference counter (semaphore)

From: Song Liu
Date: Tue Aug 21 2018 - 17:33:46 EST

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In reply to: Ravi Bangoria: "[PATCH v9 4/4] perf probe: Support SDT markers having reference counter (semaphore)"
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On Sun, Aug 19, 2018 at 9:42 PM, Ravi Bangoria
<ravi.bangoria@xxxxxxxxxxxxx> wrote:
> With this, perf buildid-cache will save SDT markers with reference
> counter in probe cache. Perf probe will be able to probe markers
> having reference counter. Ex,
>
> # readelf -n /tmp/tick | grep -A1 loop2
> Name: loop2
> ... Semaphore: 0x0000000010020036
>
> # ./perf buildid-cache --add /tmp/tick
> # ./perf probe sdt_tick:loop2
> # ./perf stat -e sdt_tick:loop2 /tmp/tick
> hi: 0
> hi: 1
> hi: 2
> ^C
> Performance counter stats for '/tmp/tick':
> 3 sdt_tick:loop2
> 2.561851452 seconds time elapsed
>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxx>
> Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> Acked-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>

Reviewed-and-tested-by: Song Liu <songliubraving@xxxxxx>

> ---
> tools/perf/util/probe-event.c | 39 ++++++++++++++++++++++++++++++++----
> tools/perf/util/probe-event.h | 1 +
> tools/perf/util/probe-file.c | 34 ++++++++++++++++++++++++++------
> tools/perf/util/probe-file.h | 1 +
> tools/perf/util/symbol-elf.c | 46 ++++++++++++++++++++++++++++++++-----------
> tools/perf/util/symbol.h | 7 +++++++
> 6 files changed, 106 insertions(+), 22 deletions(-)
>
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index f119eb628dbb..e86f8be89157 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -1819,6 +1819,12 @@ int parse_probe_trace_command(const char *cmd, struct probe_trace_event *tev)
> tp->offset = strtoul(fmt2_str, NULL, 10);
> }
>
> + if (tev->uprobes) {
> + fmt2_str = strchr(p, '(');
> + if (fmt2_str)
> + tp->ref_ctr_offset = strtoul(fmt2_str + 1, NULL, 0);
> + }
> +
> tev->nargs = argc - 2;
> tev->args = zalloc(sizeof(struct probe_trace_arg) * tev->nargs);
> if (tev->args == NULL) {
> @@ -2012,6 +2018,22 @@ static int synthesize_probe_trace_arg(struct probe_trace_arg *arg,
> return err;
> }
>
> +static int
> +synthesize_uprobe_trace_def(struct probe_trace_event *tev, struct strbuf *buf)
> +{
> + struct probe_trace_point *tp = &tev->point;
> + int err;
> +
> + err = strbuf_addf(buf, "%s:0x%lx", tp->module, tp->address);
> +
> + if (err >= 0 && tp->ref_ctr_offset) {
> + if (!uprobe_ref_ctr_is_supported())
> + return -1;
> + err = strbuf_addf(buf, "(0x%lx)", tp->ref_ctr_offset);
> + }
> + return err >= 0 ? 0 : -1;
> +}
> +
> char *synthesize_probe_trace_command(struct probe_trace_event *tev)
> {
> struct probe_trace_point *tp = &tev->point;
> @@ -2041,15 +2063,17 @@ char *synthesize_probe_trace_command(struct probe_trace_event *tev)
> }
>
> /* Use the tp->address for uprobes */
> - if (tev->uprobes)
> - err = strbuf_addf(&buf, "%s:0x%lx", tp->module, tp->address);
> - else if (!strncmp(tp->symbol, "0x", 2))
> + if (tev->uprobes) {
> + err = synthesize_uprobe_trace_def(tev, &buf);
> + } else if (!strncmp(tp->symbol, "0x", 2)) {
> /* Absolute address. See try_to_find_absolute_address() */
> err = strbuf_addf(&buf, "%s%s0x%lx", tp->module ?: "",
> tp->module ? ":" : "", tp->address);
> - else
> + } else {
> err = strbuf_addf(&buf, "%s%s%s+%lu", tp->module ?: "",
> tp->module ? ":" : "", tp->symbol, tp->offset);
> + }
> +
> if (err)
> goto error;
>
> @@ -2633,6 +2657,13 @@ static void warn_uprobe_event_compat(struct probe_trace_event *tev)
> {
> int i;
> char *buf = synthesize_probe_trace_command(tev);
> + struct probe_trace_point *tp = &tev->point;
> +
> + if (tp->ref_ctr_offset && !uprobe_ref_ctr_is_supported()) {
> + pr_warning("A semaphore is associated with %s:%s and "
> + "seems your kernel doesn't support it.\n",
> + tev->group, tev->event);
> + }
>
> /* Old uprobe event doesn't support memory dereference */
> if (!tev->uprobes || tev->nargs == 0 || !buf)
> diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
> index 45b14f020558..15a98c3a2a2f 100644
> --- a/tools/perf/util/probe-event.h
> +++ b/tools/perf/util/probe-event.h
> @@ -27,6 +27,7 @@ struct probe_trace_point {
> char *symbol; /* Base symbol */
> char *module; /* Module name */
> unsigned long offset; /* Offset from symbol */
> + unsigned long ref_ctr_offset; /* SDT reference counter offset */
> unsigned long address; /* Actual address of the trace point */
> bool retprobe; /* Return probe flag */
> };
> diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
> index b76088fadf3d..aac7817d9e14 100644
> --- a/tools/perf/util/probe-file.c
> +++ b/tools/perf/util/probe-file.c
> @@ -696,8 +696,16 @@ int probe_cache__add_entry(struct probe_cache *pcache,
> #ifdef HAVE_GELF_GETNOTE_SUPPORT
> static unsigned long long sdt_note__get_addr(struct sdt_note *note)
> {
> - return note->bit32 ? (unsigned long long)note->addr.a32[0]
> - : (unsigned long long)note->addr.a64[0];
> + return note->bit32 ?
> + (unsigned long long)note->addr.a32[SDT_NOTE_IDX_LOC] :
> + (unsigned long long)note->addr.a64[SDT_NOTE_IDX_LOC];
> +}
> +
> +static unsigned long long sdt_note__get_ref_ctr_offset(struct sdt_note *note)
> +{
> + return note->bit32 ?
> + (unsigned long long)note->addr.a32[SDT_NOTE_IDX_REFCTR] :
> + (unsigned long long)note->addr.a64[SDT_NOTE_IDX_REFCTR];
> }
>
> static const char * const type_to_suffix[] = {
> @@ -775,14 +783,21 @@ static char *synthesize_sdt_probe_command(struct sdt_note *note,
> {
> struct strbuf buf;
> char *ret = NULL, **args;
> - int i, args_count;
> + int i, args_count, err;
> + unsigned long long ref_ctr_offset;
>
> if (strbuf_init(&buf, 32) < 0)
> return NULL;
>
> - if (strbuf_addf(&buf, "p:%s/%s %s:0x%llx",
> - sdtgrp, note->name, pathname,
> - sdt_note__get_addr(note)) < 0)
> + err = strbuf_addf(&buf, "p:%s/%s %s:0x%llx",
> + sdtgrp, note->name, pathname,
> + sdt_note__get_addr(note));
> +
> + ref_ctr_offset = sdt_note__get_ref_ctr_offset(note);
> + if (ref_ctr_offset && err >= 0)
> + err = strbuf_addf(&buf, "(0x%llx)", ref_ctr_offset);
> +
> + if (err < 0)
> goto error;
>
> if (!note->args)
> @@ -998,6 +1013,7 @@ int probe_cache__show_all_caches(struct strfilter *filter)
> enum ftrace_readme {
> FTRACE_README_PROBE_TYPE_X = 0,
> FTRACE_README_KRETPROBE_OFFSET,
> + FTRACE_README_UPROBE_REF_CTR,
> FTRACE_README_END,
> };
>
> @@ -1009,6 +1025,7 @@ static struct {
> [idx] = {.pattern = pat, .avail = false}
> DEFINE_TYPE(FTRACE_README_PROBE_TYPE_X, "*type: * x8/16/32/64,*"),
> DEFINE_TYPE(FTRACE_README_KRETPROBE_OFFSET, "*place (kretprobe): *"),
> + DEFINE_TYPE(FTRACE_README_UPROBE_REF_CTR, "*ref_ctr_offset*"),
> };
>
> static bool scan_ftrace_readme(enum ftrace_readme type)
> @@ -1064,3 +1081,8 @@ bool kretprobe_offset_is_supported(void)
> {
> return scan_ftrace_readme(FTRACE_README_KRETPROBE_OFFSET);
> }
> +
> +bool uprobe_ref_ctr_is_supported(void)
> +{
> + return scan_ftrace_readme(FTRACE_README_UPROBE_REF_CTR);
> +}
> diff --git a/tools/perf/util/probe-file.h b/tools/perf/util/probe-file.h
> index 63f29b1d22c1..2a249182f2a6 100644
> --- a/tools/perf/util/probe-file.h
> +++ b/tools/perf/util/probe-file.h
> @@ -69,6 +69,7 @@ struct probe_cache_entry *probe_cache__find_by_name(struct probe_cache *pcache,
> int probe_cache__show_all_caches(struct strfilter *filter);
> bool probe_type_is_available(enum probe_type type);
> bool kretprobe_offset_is_supported(void);
> +bool uprobe_ref_ctr_is_supported(void);
> #else /* ! HAVE_LIBELF_SUPPORT */
> static inline struct probe_cache *probe_cache__new(const char *tgt __maybe_unused, struct nsinfo *nsi __maybe_unused)
> {
> diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
> index 29770ea61768..0281d5e2cd67 100644
> --- a/tools/perf/util/symbol-elf.c
> +++ b/tools/perf/util/symbol-elf.c
> @@ -1947,6 +1947,34 @@ void kcore_extract__delete(struct kcore_extract *kce)
> }
>
> #ifdef HAVE_GELF_GETNOTE_SUPPORT
> +
> +static void sdt_adjust_loc(struct sdt_note *tmp, GElf_Addr base_off)
> +{
> + if (!base_off)
> + return;
> +
> + if (tmp->bit32)
> + tmp->addr.a32[SDT_NOTE_IDX_LOC] =
> + tmp->addr.a32[SDT_NOTE_IDX_LOC] + base_off -
> + tmp->addr.a32[SDT_NOTE_IDX_BASE];
> + else
> + tmp->addr.a64[SDT_NOTE_IDX_LOC] =
> + tmp->addr.a64[SDT_NOTE_IDX_LOC] + base_off -
> + tmp->addr.a64[SDT_NOTE_IDX_BASE];
> +}
> +
> +static void sdt_adjust_refctr(struct sdt_note *tmp, GElf_Addr base_addr,
> + GElf_Addr base_off)
> +{
> + if (!base_off)
> + return;
> +
> + if (tmp->bit32 && tmp->addr.a32[SDT_NOTE_IDX_REFCTR])
> + tmp->addr.a32[SDT_NOTE_IDX_REFCTR] -= (base_addr - base_off);
> + else if (tmp->addr.a64[SDT_NOTE_IDX_REFCTR])
> + tmp->addr.a64[SDT_NOTE_IDX_REFCTR] -= (base_addr - base_off);
> +}
> +
> /**
> * populate_sdt_note : Parse raw data and identify SDT note
> * @elf: elf of the opened file
> @@ -1964,7 +1992,6 @@ static int populate_sdt_note(Elf **elf, const char *data, size_t len,
> const char *provider, *name, *args;
> struct sdt_note *tmp = NULL;
> GElf_Ehdr ehdr;
> - GElf_Addr base_off = 0;
> GElf_Shdr shdr;
> int ret = -EINVAL;
>
> @@ -2060,17 +2087,12 @@ static int populate_sdt_note(Elf **elf, const char *data, size_t len,
> * 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_SCN, NULL)) {
> - base_off = shdr.sh_offset;
> - if (base_off) {
> - if (tmp->bit32)
> - tmp->addr.a32[0] = tmp->addr.a32[0] + base_off -
> - tmp->addr.a32[1];
> - else
> - tmp->addr.a64[0] = tmp->addr.a64[0] + base_off -
> - tmp->addr.a64[1];
> - }
> - }
> + if (elf_section_by_name(*elf, &ehdr, &shdr, SDT_BASE_SCN, NULL))
> + sdt_adjust_loc(tmp, shdr.sh_offset);
> +
> + /* Adjust reference counter offset */
> + if (elf_section_by_name(*elf, &ehdr, &shdr, SDT_PROBES_SCN, NULL))
> + sdt_adjust_refctr(tmp, shdr.sh_addr, shdr.sh_offset);
>
> list_add_tail(&tmp->note_list, sdt_notes);
> return 0;
> diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
> index f25fae4b5743..20f49779116b 100644
> --- a/tools/perf/util/symbol.h
> +++ b/tools/perf/util/symbol.h
> @@ -379,12 +379,19 @@ int get_sdt_note_list(struct list_head *head, const char *target);
> int cleanup_sdt_note_list(struct list_head *sdt_notes);
> int sdt_notes__get_count(struct list_head *start);
>
> +#define SDT_PROBES_SCN ".probes"
> #define SDT_BASE_SCN ".stapsdt.base"
> #define SDT_NOTE_SCN ".note.stapsdt"
> #define SDT_NOTE_TYPE 3
> #define SDT_NOTE_NAME "stapsdt"
> #define NR_ADDR 3
>
> +enum {
> + SDT_NOTE_IDX_LOC = 0,
> + SDT_NOTE_IDX_BASE,
> + SDT_NOTE_IDX_REFCTR,
> +};
> +
> struct mem_info *mem_info__new(void);
> struct mem_info *mem_info__get(struct mem_info *mi);
> void mem_info__put(struct mem_info *mi);
> --
> 2.14.4
>

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