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

[Hemant Kumar <hemant@linux.vnet.ibm.com>]

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