Re: [PATCH perf/core v5 10/15] perf buildid-cache: Scan and import user SDT events to probe cache

Hemant Kumar
2016-04-27T20:32:31Z

On 04/28/2016 12:08 AM, Masami Hiramatsu wrote:
> From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
>
> perf buildid-cache --add <binary> scans given binary and add
> the SDT events to probe cache. "sdt_" prefix is appended for
> all SDT providers to avoid event-name clash with other pre-defined
> events. It is possible to use the cached SDT events as other cached
> events, via perf probe --add "sdt_<provider>:<event>=<event>".
>
> e.g.
> ----
> # perf buildid-cache --add /lib/libc-2.17.so
> # perf probe --cache --list | head -n 5
> /usr/lib/libc-2.17.so (a6fb821bdf53660eb2c29f778757aef294d3d392):
> sdt_libc:setjmp=setjmp
> sdt_libc:longjmp=longjmp
> sdt_libc:longjmp_target=longjmp_target
> sdt_libc:memory_heap_new=memory_heap_new
> # perf probe -x /usr/lib/libc-2.17.so \
> -a sdt_libc:memory_heap_new=memory_heap_new
> Added new event:
> sdt_libc:memory_heap_new (on memory_heap_new
> in /usr/lib/libc-2.17.so)
>
> You can now use it in all perf tools, such as:
>
> perf record -e sdt_libc:memory_heap_new -aR sleep 1
>
> # perf probe -l
> sdt_libc:memory_heap_new (on new_heap+183 in /usr/lib/libc-2.17.so)
> ----
>
> Note that SDT event entries in probe-cache file is somewhat different
> from normal cached events. Normal one starts with "#", but SDTs are
> starting with "%".
>
> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
> Changes in v4:
> - Fix a bug to copy correct group name to entries.
> - Fix to consolidate same-name entries.

Acked-by: Hemant Kumar <hemant@linux.vnet.ibm.com>

> ---
> tools/perf/util/build-id.c | 27 +++++++++++++++--
> tools/perf/util/probe-file.c | 67 ++++++++++++++++++++++++++++++++++++++++--
> tools/perf/util/probe-file.h | 2 +
> 3 files changed, 90 insertions(+), 6 deletions(-)
>
> diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
> index a7da315..49a467b9 100644
> --- a/tools/perf/util/build-id.c
> +++ b/tools/perf/util/build-id.c
> @@ -17,6 +17,7 @@
> #include "tool.h"
> #include "header.h"
> #include "vdso.h"
> +#include "probe-file.h"
>
>
> static bool no_buildid_cache;
> @@ -490,6 +491,23 @@ int build_id_cache__list_build_ids(const char *pathname,
> return ret;
> }
>
> +#ifdef HAVE_LIBELF_SUPPORT
> +static void build_id_cache__add_sdt_cache(const char *sbuild_id,
> + const char *realname)
> +{
> + struct probe_cache *cache;
> +
> + cache = probe_cache__new(sbuild_id);
> + if (!cache)
> + return;
> + if (probe_cache__scan_sdt(cache, realname) >= 0)
> + probe_cache__commit(cache);
> + probe_cache__delete(cache);
> +}
> +#else
> +#define build_id_cache__add_sdt_cache(sbuild_id, realname) do { } while (0)
> +#endif
> +
> int build_id_cache__add_s(const char *sbuild_id, const char *name,
> bool is_kallsyms, bool is_vdso)
> {
> @@ -533,20 +551,23 @@ int build_id_cache__add_s(const char *sbuild_id, const char *name,
> goto out_free;
> }
>
> + /* Make a symbolic link */
> if (!build_id_cache__linkname(sbuild_id, linkname, size))
> goto out_free;
> +
> tmp = strrchr(linkname, '/');
> *tmp = '\0';
> -
> if (access(linkname, X_OK) && mkdir_p(linkname, 0755))
> goto out_free;
> -
> *tmp = '/';
> tmp = dir_name + strlen(buildid_dir) - 5;
> memcpy(tmp, "../..", 5);
> -
> if (symlink(tmp, linkname) == 0)
> err = 0;
> +
> + /* Update SDT cache */
> + build_id_cache__add_sdt_cache(sbuild_id, realname);
> +
> out_free:
> if (!is_kallsyms)
> free(realname);
> diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
> index 46f006e..c10a647 100644
> --- a/tools/perf/util/probe-file.c
> +++ b/tools/perf/util/probe-file.c
> @@ -428,9 +428,12 @@ static int probe_cache__load(struct probe_cache *pcache)
> p = strchr(buf, '\n');
> if (p)
> *p = '\0';
> - if (buf[0] == '#') { /* #perf_probe_event */
> + /* #perf_probe_event or %sdt_event */
> + if (buf[0] == '#' || buf[0] == '%') {
> entry = probe_cache_entry__new(NULL);
> entry->spev = strdup(buf + 1);
> + if (buf[0] == '%')
> + entry->sdt = true;
> ret = parse_perf_probe_command(buf + 1, &entry->pev);
> if (!entry->spev || ret < 0) {
> probe_cache_entry__delete(entry);
> @@ -602,14 +605,72 @@ out_err:
> return ret;
> }
>
> +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];
> +}
> +
> +int probe_cache__scan_sdt(struct probe_cache *pcache, const char *pathname)
> +{
> + struct probe_cache_entry *entry = NULL;
> + struct list_head sdtlist;
> + struct sdt_note *note;
> + char *buf;
> + char sdtgrp[64];
> + int ret;
> +
> + INIT_LIST_HEAD(&sdtlist);
> + ret = get_sdt_note_list(&sdtlist, pathname);
> + if (ret < 0) {
> + pr_debug("Failed to get sdt note: %d\n", ret);
> + return ret;
> + }
> + list_for_each_entry(note, &sdtlist, note_list) {
> + ret = snprintf(sdtgrp, 64, "sdt_%s", note->provider);
> + if (ret < 0)
> + break;
> + /* Try to find same-name entry */
> + entry = probe_cache__find_by_name(pcache, sdtgrp, note->name);
> + if (!entry) {
> + entry = probe_cache_entry__new(NULL);
> + if (!entry) {
> + ret = -ENOMEM;
> + break;
> + }
> + entry->sdt = true;
> + ret = asprintf(&entry->spev, "%s:%s=%s", sdtgrp,
> + note->name, note->name);
> + if (ret < 0)
> + break;
> + entry->pev.event = strdup(note->name);
> + entry->pev.group = strdup(sdtgrp);
> + list_add_tail(&entry->list, &pcache->list);
> + }
> + ret = asprintf(&buf, "p:%s/%s %s:0x%llx",
> + sdtgrp, note->name, pathname,
> + sdt_note__get_addr(note));
> + if (ret < 0)
> + break;
> + strlist__add(entry->tevlist, buf);
> + free(buf);
> + entry = NULL;
> + }
> + if (entry)
> + probe_cache_entry__delete(entry);
> + cleanup_sdt_note_list(&sdtlist);
> + return ret;
> +}
> +
> static int probe_cache_entry__write(struct probe_cache_entry *entry, int fd)
> {
> struct str_node *snode;
> struct iovec iov[3];
> + const char *prefix = entry->sdt ? "%" : "#";
> int ret;
>
> - pr_debug("Writing cache: #%s\n", entry->spev);
> - iov[0].iov_base = (void *)"#"; iov[0].iov_len = 1;
> + pr_debug("Writing cache: %s%s\n", prefix, entry->spev);
> + iov[0].iov_base = (void *)prefix; iov[0].iov_len = 1;
> iov[1].iov_base = entry->spev; iov[1].iov_len = strlen(entry->spev);
> iov[2].iov_base = (void *)"\n"; iov[2].iov_len = 1;
> ret = writev(fd, iov, 3);
> diff --git a/tools/perf/util/probe-file.h b/tools/perf/util/probe-file.h
> index e6fd9b9..93aa193 100644
> --- a/tools/perf/util/probe-file.h
> +++ b/tools/perf/util/probe-file.h
> @@ -8,6 +8,7 @@
> /* Cache of probe definitions */
> struct probe_cache_entry {
> struct list_head list;
> + bool sdt;
> struct perf_probe_event pev;
> char *spev;
> struct strlist *tevlist;
> @@ -35,6 +36,7 @@ struct probe_cache *probe_cache__new(const char *target);
> int probe_cache__add_entry(struct probe_cache *pcache,
> struct perf_probe_event *pev,
> struct probe_trace_event *tevs, int ntevs);
> +int probe_cache__scan_sdt(struct probe_cache *pcache, const char *pathname);
> int probe_cache__commit(struct probe_cache *pcache);
> void probe_cache__delete(struct probe_cache *pcache);
> int probe_cache__remove_entries(struct probe_cache *pcache,
>

--
Thanks,
Hemant Kumar