[PATCH v4] perf-probe: Support escaped character in parser

[PATCH v4] perf-probe: Support escaped character in parser

[Masami Hiramatsu]

Support the special characters escaped by '\' in parser.
This allows user to specify versions directly like below.

  =====
  # ./perf probe -x /lib64/libc-2.25.so malloc_get_state\\@GLIBC_2.2.5
  Added new event:
    probe_libc:malloc_get_state (on malloc_get_state@GLIBC_2.2.5 in /usr/lib64/libc-2.25.so)

  You can now use it in all perf tools, such as:

	  perf record -e probe_libc:malloc_get_state -aR sleep 1

  =====

Or, you can use separators in source filename, e.g.

  =====
  # ./perf probe -x /opt/test/a.out foo+bar.c:3
  Semantic error :There is non-digit character in offset.
    Error: Command Parse Error.
  =====

Usually "+" in source file cause parser error, but

  =====
  # ./perf probe -x /opt/test/a.out foo\\+bar.c:4
  Added new event:
    probe_a:main         (on @foo+bar.c:4 in /opt/test/a.out)

  You can now use it in all perf tools, such as:

	  perf record -e probe_a:main -aR sleep 1
  =====

escaped "\+" allows you to specify that.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
Acked-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
---
 Changes in v2:
  - Add a description and samples in Documentation/perf-probe.txt
 Changes in v3:
  - Update for new series.
 Changes in v4:
  - Fix a build error (Thanks for Arnaldo!)
    This time, I ensured that I ran "make build-test" and it passed.
---
 tools/perf/Documentation/perf-probe.txt |   16 +++++++++
 tools/perf/util/probe-event.c           |   58 +++++++++++++++++++------------
 2 files changed, 51 insertions(+), 23 deletions(-)

diff --git a/tools/perf/Documentation/perf-probe.txt b/tools/perf/Documentation/perf-probe.txt
index f96382692f42..b6866a05edd2 100644
--- a/tools/perf/Documentation/perf-probe.txt
+++ b/tools/perf/Documentation/perf-probe.txt
@@ -182,6 +182,14 @@ Note that before using the SDT event, the target binary (on which SDT events are
 For details of the SDT, see below.
 https://sourceware.org/gdb/onlinedocs/gdb/Static-Probe-Points.html
 
+ESCAPED CHARACTER
+-----------------
+
+In the probe syntax, '=', '@', '+', ':' and ';' are treated as a special character. You can use a backslash ('\') to escape the special characters.
+This is useful if you need to probe on a specific versioned symbols, like @GLIBC_... suffixes, or also you need to specify a source file which includes the special characters.
+Note that usually single backslash is consumed by shell, so you might need to pass double backslash (\\) or wrapping with single quotes (\'AAA\@BBB').
+See EXAMPLES how it is used.
+
 PROBE ARGUMENT
 --------------
 Each probe argument follows below syntax.
@@ -277,6 +285,14 @@ Add a USDT probe to a target process running in a different mount namespace
 
  ./perf probe --target-ns <target pid> -x /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.121-0.b13.el7_3.x86_64/jre/lib/amd64/server/libjvm.so %sdt_hotspot:thread__sleep__end
 
+Add a probe on specific versioned symbol by backslash escape
+
+ ./perf probe -x /lib64/libc-2.25.so 'malloc_get_state\@GLIBC_2.2.5'
+
+Add a probe in a source file using special characters by backslash escape
+
+ ./perf probe -x /opt/test/a.out 'foo\+bar.c:4'
+
 
 SEE ALSO
 --------
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 0d6c66d51939..e1dbc9821617 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -1325,27 +1325,30 @@ static int parse_perf_probe_event_name(char **arg, struct perf_probe_event *pev)
 {
 	char *ptr;
 
-	ptr = strchr(*arg, ':');
+	ptr = strpbrk_esc(*arg, ":");
 	if (ptr) {
 		*ptr = '\0';
 		if (!pev->sdt && !is_c_func_name(*arg))
 			goto ng_name;
-		pev->group = strdup(*arg);
+		pev->group = strdup_esc(*arg);
 		if (!pev->group)
 			return -ENOMEM;
 		*arg = ptr + 1;
 	} else
 		pev->group = NULL;
-	if (!pev->sdt && !is_c_func_name(*arg)) {
+
+	pev->event = strdup_esc(*arg);
+	if (pev->event == NULL)
+		return -ENOMEM;
+
+	if (!pev->sdt && !is_c_func_name(pev->event)) {
+		zfree(&pev->event);
 ng_name:
+		zfree(&pev->group);
 		semantic_error("%s is bad for event name -it must "
 			       "follow C symbol-naming rule.\n", *arg);
 		return -EINVAL;
 	}
-	pev->event = strdup(*arg);
-	if (pev->event == NULL)
-		return -ENOMEM;
-
 	return 0;
 }
 
@@ -1373,7 +1376,7 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
 			arg++;
 	}
 
-	ptr = strpbrk(arg, ";=@+%");
+	ptr = strpbrk_esc(arg, ";=@+%");
 	if (pev->sdt) {
 		if (ptr) {
 			if (*ptr != '@') {
@@ -1387,7 +1390,7 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
 				pev->target = build_id_cache__origname(tmp);
 				free(tmp);
 			} else
-				pev->target = strdup(ptr + 1);
+				pev->target = strdup_esc(ptr + 1);
 			if (!pev->target)
 				return -ENOMEM;
 			*ptr = '\0';
@@ -1421,13 +1424,14 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
 	 *
 	 * Otherwise, we consider arg to be a function specification.
 	 */
-	if (!strpbrk(arg, "+@%") && (ptr = strpbrk(arg, ";:")) != NULL) {
+	if (!strpbrk_esc(arg, "+@%")) {
+		ptr = strpbrk_esc(arg, ";:");
 		/* This is a file spec if it includes a '.' before ; or : */
-		if (memchr(arg, '.', ptr - arg))
+		if (ptr && memchr(arg, '.', ptr - arg))
 			file_spec = true;
 	}
 
-	ptr = strpbrk(arg, ";:+@%");
+	ptr = strpbrk_esc(arg, ";:+@%");
 	if (ptr) {
 		nc = *ptr;
 		*ptr++ = '\0';
@@ -1436,7 +1440,7 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
 	if (arg[0] == '\0')
 		tmp = NULL;
 	else {
-		tmp = strdup(arg);
+		tmp = strdup_esc(arg);
 		if (tmp == NULL)
 			return -ENOMEM;
 	}
@@ -1469,12 +1473,12 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
 		arg = ptr;
 		c = nc;
 		if (c == ';') {	/* Lazy pattern must be the last part */
-			pp->lazy_line = strdup(arg);
+			pp->lazy_line = strdup(arg); /* let leave escapes */
 			if (pp->lazy_line == NULL)
 				return -ENOMEM;
 			break;
 		}
-		ptr = strpbrk(arg, ";:+@%");
+		ptr = strpbrk_esc(arg, ";:+@%");
 		if (ptr) {
 			nc = *ptr;
 			*ptr++ = '\0';
@@ -1501,7 +1505,7 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
 				semantic_error("SRC@SRC is not allowed.\n");
 				return -EINVAL;
 			}
-			pp->file = strdup(arg);
+			pp->file = strdup_esc(arg);
 			if (pp->file == NULL)
 				return -ENOMEM;
 			break;
@@ -2803,23 +2807,31 @@ static int find_probe_functions(struct map *map, char *name,
 	struct rb_node *tmp;
 	const char *norm, *ver;
 	char *buf = NULL;
+	bool cut_version = true;
 
 	if (map__load(map) < 0)
 		return 0;
 
+	/* If user gives a version, don't cut off the version from symbols */
+	if (strchr(name, '@'))
+		cut_version = false;
+
 	map__for_each_symbol(map, sym, tmp) {
 		norm = arch__normalize_symbol_name(sym->name);
 		if (!norm)
 			continue;
 
-		/* We don't care about default symbol or not */
-		ver = strchr(norm, '@');
-		if (ver) {
-			buf = strndup(norm, ver - norm);
-			if (!buf)
-				return -ENOMEM;
-			norm = buf;
+		if (cut_version) {
+			/* We don't care about default symbol or not */
+			ver = strchr(norm, '@');
+			if (ver) {
+				buf = strndup(norm, ver - norm);
+				if (!buf)
+					return -ENOMEM;
+				norm = buf;
+			}
 		}
+
 		if (strglobmatch(norm, name)) {
 			found++;
 			if (syms && found < probe_conf.max_probes)

Re: [PATCH v4] perf-probe: Support escaped character in parser

[Arnaldo Carvalho de Melo]

Em Wed, Dec 13, 2017 at 12:05:12AM +0900, Masami Hiramatsu escreveu:
> Support the special characters escaped by '\' in parser.
> This allows user to specify versions directly like below.
> 
>   =====
>   # ./perf probe -x /lib64/libc-2.25.so malloc_get_state\\@GLIBC_2.2.5
>   Added new event:
>     probe_libc:malloc_get_state (on malloc_get_state@GLIBC_2.2.5 in /usr/lib64/libc-2.25.so)
> 
>   You can now use it in all perf tools, such as:
> 
> 	  perf record -e probe_libc:malloc_get_state -aR sleep 1
> 
>   =====
> 
> Or, you can use separators in source filename, e.g.
> 
>   =====
>   # ./perf probe -x /opt/test/a.out foo+bar.c:3
>   Semantic error :There is non-digit character in offset.
>     Error: Command Parse Error.
>   =====
> 
> Usually "+" in source file cause parser error, but
> 
>   =====
>   # ./perf probe -x /opt/test/a.out foo\\+bar.c:4
>   Added new event:
>     probe_a:main         (on @foo+bar.c:4 in /opt/test/a.out)
> 
>   You can now use it in all perf tools, such as:
> 
> 	  perf record -e probe_a:main -aR sleep 1
>   =====
> 
> escaped "\+" allows you to specify that.

<SNIP>
 
>  Changes in v4:
>   - Fix a build error (Thanks for Arnaldo!)
>     This time, I ensured that I ran "make build-test" and it passed.

Thanks, testing it I still have that artifact:

 ---------------------------------------

[root@jouet perf]# perf probe -x /lib64/libc-2.25.so malloc_get_state\\@GLIBC_2.2.5
Added new event:
  probe_libc:malloc_get_state (on malloc_get_state@GLIBC_2.2.5 in /usr/lib64/libc-2.25.so)

You can now use it in all perf tools, such as:

	perf record -e probe_libc:malloc_get_state -aR sleep 1

[root@jouet perf]# perf probe -l
Failed to find debug information for address dd38eca7
  probe_libc:malloc_get_state (on 0xdd38eca7 in /usr/lib64/libc-2.25.so)
[root@jouet perf]#

 ---------------------------------------

I mean the "on 0xdd38eca7" part:


That failed to find debug information part:

[root@jouet perf]# perf probe -vv -l
Add filter: *
Opening /sys/kernel/debug/tracing//kprobe_events write=0
Opening /sys/kernel/debug/tracing//uprobe_events write=0
Parsing probe_events: p:probe_libc/malloc_get_state /usr/lib64/libc-2.25.so:0x00000000dd38eca7
Group:probe_libc Event:malloc_get_state probe:p
try to find information at dd38eca7 in /usr/lib64/libc-2.25.so
Open Debuginfo file: /usr/lib/debug/usr/lib64/libc-2.25.so.debug
Failed to find debug information for address dd38eca7
Failed to find corresponding probes from debuginfo.
symsrc__init: build id mismatch for /usr/lib/debug/usr/lib64/libc-2.25.so.debug.
Failed to find probe point from both of dwarf and map.
  probe_libc:malloc_get_state (on 0xdd38eca7 in /usr/lib64/libc-2.25.so)
[root@jouet perf]#

Ok, so build-id mismatch, lets see:

[root@jouet perf]# rpm -q glibc glibc-debuginfo
glibc-2.25-10.fc26.x86_64
glibc-2.25-10.fc26.i686
glibc-debuginfo-2.25-12.fc26.x86_64
[root@jouet perf]#

Ok, the debuginfo file is newer than the glibc installed, updating glibc
now...

We could have a more informative message in this case, right? I.e.
something like:

[root@jouet perf]# perf probe -l
There was a build-id mismatch while trying to resolve 0xdd38eca7, please
check your system's debuginfo files for mismatches, e.g. check the
versions for glibc and glibc-debuginfo.
  probe_libc:malloc_get_state (on 0xdd38eca7 in /usr/lib64/libc-2.25.so)
[root@jouet perf]#

- Arnaldo

Re: [PATCH v4] perf-probe: Support escaped character in parser

[Masami Hiramatsu]

On Tue, 12 Dec 2017 12:27:24 -0300
Arnaldo Carvalho de Melo <acme@kernel.org> wrote:

> Em Wed, Dec 13, 2017 at 12:05:12AM +0900, Masami Hiramatsu escreveu:
> > Support the special characters escaped by '\' in parser.
> > This allows user to specify versions directly like below.
> > 
> >   =====
> >   # ./perf probe -x /lib64/libc-2.25.so malloc_get_state\\@GLIBC_2.2.5
> >   Added new event:
> >     probe_libc:malloc_get_state (on malloc_get_state@GLIBC_2.2.5 in /usr/lib64/libc-2.25.so)
> > 
> >   You can now use it in all perf tools, such as:
> > 
> > 	  perf record -e probe_libc:malloc_get_state -aR sleep 1
> > 
> >   =====
> > 
> > Or, you can use separators in source filename, e.g.
> > 
> >   =====
> >   # ./perf probe -x /opt/test/a.out foo+bar.c:3
> >   Semantic error :There is non-digit character in offset.
> >     Error: Command Parse Error.
> >   =====
> > 
> > Usually "+" in source file cause parser error, but
> > 
> >   =====
> >   # ./perf probe -x /opt/test/a.out foo\\+bar.c:4
> >   Added new event:
> >     probe_a:main         (on @foo+bar.c:4 in /opt/test/a.out)
> > 
> >   You can now use it in all perf tools, such as:
> > 
> > 	  perf record -e probe_a:main -aR sleep 1
> >   =====
> > 
> > escaped "\+" allows you to specify that.
> 
> <SNIP>
>  
> >  Changes in v4:
> >   - Fix a build error (Thanks for Arnaldo!)
> >     This time, I ensured that I ran "make build-test" and it passed.
> 
> Thanks, testing it I still have that artifact:
> 
>  ---------------------------------------
> 
> [root@jouet perf]# perf probe -x /lib64/libc-2.25.so malloc_get_state\\@GLIBC_2.2.5
> Added new event:
>   probe_libc:malloc_get_state (on malloc_get_state@GLIBC_2.2.5 in /usr/lib64/libc-2.25.so)
> 
> You can now use it in all perf tools, such as:
> 
> 	perf record -e probe_libc:malloc_get_state -aR sleep 1
> 
> [root@jouet perf]# perf probe -l
> Failed to find debug information for address dd38eca7
>   probe_libc:malloc_get_state (on 0xdd38eca7 in /usr/lib64/libc-2.25.so)
> [root@jouet perf]#
> 
>  ---------------------------------------
> 
> I mean the "on 0xdd38eca7" part:
> 
> 
> That failed to find debug information part:
> 
> [root@jouet perf]# perf probe -vv -l
> Add filter: *
> Opening /sys/kernel/debug/tracing//kprobe_events write=0
> Opening /sys/kernel/debug/tracing//uprobe_events write=0
> Parsing probe_events: p:probe_libc/malloc_get_state /usr/lib64/libc-2.25.so:0x00000000dd38eca7
> Group:probe_libc Event:malloc_get_state probe:p
> try to find information at dd38eca7 in /usr/lib64/libc-2.25.so
> Open Debuginfo file: /usr/lib/debug/usr/lib64/libc-2.25.so.debug
> Failed to find debug information for address dd38eca7
> Failed to find corresponding probes from debuginfo.
> symsrc__init: build id mismatch for /usr/lib/debug/usr/lib64/libc-2.25.so.debug.
> Failed to find probe point from both of dwarf and map.
>   probe_libc:malloc_get_state (on 0xdd38eca7 in /usr/lib64/libc-2.25.so)
> [root@jouet perf]#

Ah, I got it. So symsrc__init checks debugfile to get symbols,
but failed.

> 
> Ok, so build-id mismatch, lets see:
> 
> [root@jouet perf]# rpm -q glibc glibc-debuginfo
> glibc-2.25-10.fc26.x86_64
> glibc-2.25-10.fc26.i686
> glibc-debuginfo-2.25-12.fc26.x86_64
> [root@jouet perf]#
> 
> Ok, the debuginfo file is newer than the glibc installed, updating glibc
> now...
> 
> We could have a more informative message in this case, right? I.e.
> something like:
> 
> [root@jouet perf]# perf probe -l
> There was a build-id mismatch while trying to resolve 0xdd38eca7, please
> check your system's debuginfo files for mismatches, e.g. check the
> versions for glibc and glibc-debuginfo.
>   probe_libc:malloc_get_state (on 0xdd38eca7 in /usr/lib64/libc-2.25.so)

OK, I'll try to check how debuginfo is searched in such environment.

Thank you,

> [root@jouet perf]#
> 
> - Arnaldo


-- 
Masami Hiramatsu <mhiramat@kernel.org>

Re: [PATCH v4] perf-probe: Support escaped character in parser

[Arnaldo Carvalho de Melo]

Em Wed, Dec 13, 2017 at 10:40:24PM +0900, Masami Hiramatsu escreveu:
> On Tue, 12 Dec 2017 12:27:24 -0300
> Arnaldo Carvalho de Melo <acme@kernel.org> wrote:
> 
> > Em Wed, Dec 13, 2017 at 12:05:12AM +0900, Masami Hiramatsu escreveu:
> > > Support the special characters escaped by '\' in parser.
> > > This allows user to specify versions directly like below.
> > > 
> > >   =====
> > >   # ./perf probe -x /lib64/libc-2.25.so malloc_get_state\\@GLIBC_2.2.5
> > >   Added new event:
> > >     probe_libc:malloc_get_state (on malloc_get_state@GLIBC_2.2.5 in /usr/lib64/libc-2.25.so)
> > > 
> > >   You can now use it in all perf tools, such as:
> > > 
> > > 	  perf record -e probe_libc:malloc_get_state -aR sleep 1
> > > 
> > >   =====
> > > 
> > > Or, you can use separators in source filename, e.g.
> > > 
> > >   =====
> > >   # ./perf probe -x /opt/test/a.out foo+bar.c:3
> > >   Semantic error :There is non-digit character in offset.
> > >     Error: Command Parse Error.
> > >   =====
> > > 
> > > Usually "+" in source file cause parser error, but
> > > 
> > >   =====
> > >   # ./perf probe -x /opt/test/a.out foo\\+bar.c:4
> > >   Added new event:
> > >     probe_a:main         (on @foo+bar.c:4 in /opt/test/a.out)
> > > 
> > >   You can now use it in all perf tools, such as:
> > > 
> > > 	  perf record -e probe_a:main -aR sleep 1
> > >   =====
> > > 
> > > escaped "\+" allows you to specify that.
> > 
> > <SNIP>
> >  
> > >  Changes in v4:
> > >   - Fix a build error (Thanks for Arnaldo!)
> > >     This time, I ensured that I ran "make build-test" and it passed.
> > 
> > Thanks, testing it I still have that artifact:
> > 
> >  ---------------------------------------
> > 
> > [root@jouet perf]# perf probe -x /lib64/libc-2.25.so malloc_get_state\\@GLIBC_2.2.5
> > Added new event:
> >   probe_libc:malloc_get_state (on malloc_get_state@GLIBC_2.2.5 in /usr/lib64/libc-2.25.so)
> > 
> > You can now use it in all perf tools, such as:
> > 
> > 	perf record -e probe_libc:malloc_get_state -aR sleep 1
> > 
> > [root@jouet perf]# perf probe -l
> > Failed to find debug information for address dd38eca7
> >   probe_libc:malloc_get_state (on 0xdd38eca7 in /usr/lib64/libc-2.25.so)
> > [root@jouet perf]#
> > 
> >  ---------------------------------------
> > 
> > I mean the "on 0xdd38eca7" part:
> > 
> > 
> > That failed to find debug information part:
> > 
> > [root@jouet perf]# perf probe -vv -l
> > Add filter: *
> > Opening /sys/kernel/debug/tracing//kprobe_events write=0
> > Opening /sys/kernel/debug/tracing//uprobe_events write=0
> > Parsing probe_events: p:probe_libc/malloc_get_state /usr/lib64/libc-2.25.so:0x00000000dd38eca7
> > Group:probe_libc Event:malloc_get_state probe:p
> > try to find information at dd38eca7 in /usr/lib64/libc-2.25.so
> > Open Debuginfo file: /usr/lib/debug/usr/lib64/libc-2.25.so.debug
> > Failed to find debug information for address dd38eca7
> > Failed to find corresponding probes from debuginfo.
> > symsrc__init: build id mismatch for /usr/lib/debug/usr/lib64/libc-2.25.so.debug.
> > Failed to find probe point from both of dwarf and map.
> >   probe_libc:malloc_get_state (on 0xdd38eca7 in /usr/lib64/libc-2.25.so)
> > [root@jouet perf]#
> 
> Ah, I got it. So symsrc__init checks debugfile to get symbols,
> but failed.
> 
> > 
> > Ok, so build-id mismatch, lets see:
> > 
> > [root@jouet perf]# rpm -q glibc glibc-debuginfo
> > glibc-2.25-10.fc26.x86_64
> > glibc-2.25-10.fc26.i686
> > glibc-debuginfo-2.25-12.fc26.x86_64
> > [root@jouet perf]#
> > 
> > Ok, the debuginfo file is newer than the glibc installed, updating glibc
> > now...
> > 
> > We could have a more informative message in this case, right? I.e.
> > something like:
> > 
> > [root@jouet perf]# perf probe -l
> > There was a build-id mismatch while trying to resolve 0xdd38eca7, please
> > check your system's debuginfo files for mismatches, e.g. check the
> > versions for glibc and glibc-debuginfo.
> >   probe_libc:malloc_get_state (on 0xdd38eca7 in /usr/lib64/libc-2.25.so)
> 
> OK, I'll try to check how debuginfo is searched in such environment.

So, tools/perf/util/symbol.c, function dso__load(), it will have this
loop:


        /*
         * Read the build id if possible. This is required for
         * DSO_BINARY_TYPE__BUILDID_DEBUGINFO to work
         */
        if (!dso->has_build_id && is_regular_file(dso->long_name)) {
            __symbol__join_symfs(name, PATH_MAX, dso->long_name);
            if (filename__read_build_id(name, build_id, BUILD_ID_SIZE) > 0)
                dso__set_build_id(dso, build_id);
        }

        /*
         * Iterate over candidate debug images.
         * Keep track of "interesting" ones (those which have a symtab, dynsym,
         * and/or opd section) for processing.
         */
        for (i = 0; i < DSO_BINARY_TYPE__SYMTAB_CNT; i++) {

                if (dso__read_binary_type_filename(dso, symtab_type, root_dir, name, PATH_MAX))


-------------------

So the glibc file _has_ a build id, it reads it and then will try to
find a file that has that build id, that 'name' variable will have
the file being tried, which may be, for instance, at:

[acme@jouet ~]$ perf buildid-list -i /lib64/libc-2.25.so 
7a4787e7c1263dc25461a7b2f2abd2acaa186102
[acme@jouet ~]$ ls -la /usr/lib/debug/.build-id/7a/4787e7c1263dc25461a7b2f2abd2acaa186102
lrwxrwxrwx. 1 root root 33 Oct 11 09:49 /usr/lib/debug/.build-id/7a/4787e7c1263dc25461a7b2f2abd2acaa186102 -> ../../../../../lib64/libc-2.25.so
[acme@jouet ~]$ 

etc.

So perhaps we can have a routine that does just that loop and prints the
files it finds with the debuginfo they have to help tell which files
where considered?

But perhaps the message I suggested may be good enough?

- Arnaldo

Re: [PATCH v4] perf-probe: Support escaped character in parser

[Masami Hiramatsu]

On Wed, 13 Dec 2017 12:42:27 -0300
Arnaldo Carvalho de Melo <acme@kernel.org> wrote:

> Em Wed, Dec 13, 2017 at 10:40:24PM +0900, Masami Hiramatsu escreveu:
> > On Tue, 12 Dec 2017 12:27:24 -0300
> > Arnaldo Carvalho de Melo <acme@kernel.org> wrote:
> > 
> > > Em Wed, Dec 13, 2017 at 12:05:12AM +0900, Masami Hiramatsu escreveu:
> > > > Support the special characters escaped by '\' in parser.
> > > > This allows user to specify versions directly like below.
> > > > 
> > > >   =====
> > > >   # ./perf probe -x /lib64/libc-2.25.so malloc_get_state\\@GLIBC_2.2.5
> > > >   Added new event:
> > > >     probe_libc:malloc_get_state (on malloc_get_state@GLIBC_2.2.5 in /usr/lib64/libc-2.25.so)
> > > > 
> > > >   You can now use it in all perf tools, such as:
> > > > 
> > > > 	  perf record -e probe_libc:malloc_get_state -aR sleep 1
> > > > 
> > > >   =====
> > > > 
> > > > Or, you can use separators in source filename, e.g.
> > > > 
> > > >   =====
> > > >   # ./perf probe -x /opt/test/a.out foo+bar.c:3
> > > >   Semantic error :There is non-digit character in offset.
> > > >     Error: Command Parse Error.
> > > >   =====
> > > > 
> > > > Usually "+" in source file cause parser error, but
> > > > 
> > > >   =====
> > > >   # ./perf probe -x /opt/test/a.out foo\\+bar.c:4
> > > >   Added new event:
> > > >     probe_a:main         (on @foo+bar.c:4 in /opt/test/a.out)
> > > > 
> > > >   You can now use it in all perf tools, such as:
> > > > 
> > > > 	  perf record -e probe_a:main -aR sleep 1
> > > >   =====
> > > > 
> > > > escaped "\+" allows you to specify that.
> > > 
> > > <SNIP>
> > >  
> > > >  Changes in v4:
> > > >   - Fix a build error (Thanks for Arnaldo!)
> > > >     This time, I ensured that I ran "make build-test" and it passed.
> > > 
> > > Thanks, testing it I still have that artifact:
> > > 
> > >  ---------------------------------------
> > > 
> > > [root@jouet perf]# perf probe -x /lib64/libc-2.25.so malloc_get_state\\@GLIBC_2.2.5
> > > Added new event:
> > >   probe_libc:malloc_get_state (on malloc_get_state@GLIBC_2.2.5 in /usr/lib64/libc-2.25.so)
> > > 
> > > You can now use it in all perf tools, such as:
> > > 
> > > 	perf record -e probe_libc:malloc_get_state -aR sleep 1
> > > 
> > > [root@jouet perf]# perf probe -l
> > > Failed to find debug information for address dd38eca7
> > >   probe_libc:malloc_get_state (on 0xdd38eca7 in /usr/lib64/libc-2.25.so)
> > > [root@jouet perf]#
> > > 
> > >  ---------------------------------------
> > > 
> > > I mean the "on 0xdd38eca7" part:
> > > 
> > > 
> > > That failed to find debug information part:
> > > 
> > > [root@jouet perf]# perf probe -vv -l
> > > Add filter: *
> > > Opening /sys/kernel/debug/tracing//kprobe_events write=0
> > > Opening /sys/kernel/debug/tracing//uprobe_events write=0
> > > Parsing probe_events: p:probe_libc/malloc_get_state /usr/lib64/libc-2.25.so:0x00000000dd38eca7
> > > Group:probe_libc Event:malloc_get_state probe:p
> > > try to find information at dd38eca7 in /usr/lib64/libc-2.25.so
> > > Open Debuginfo file: /usr/lib/debug/usr/lib64/libc-2.25.so.debug
> > > Failed to find debug information for address dd38eca7
> > > Failed to find corresponding probes from debuginfo.
> > > symsrc__init: build id mismatch for /usr/lib/debug/usr/lib64/libc-2.25.so.debug.
> > > Failed to find probe point from both of dwarf and map.
> > >   probe_libc:malloc_get_state (on 0xdd38eca7 in /usr/lib64/libc-2.25.so)
> > > [root@jouet perf]#
> > 
> > Ah, I got it. So symsrc__init checks debugfile to get symbols,
> > but failed.
> > 
> > > 
> > > Ok, so build-id mismatch, lets see:
> > > 
> > > [root@jouet perf]# rpm -q glibc glibc-debuginfo
> > > glibc-2.25-10.fc26.x86_64
> > > glibc-2.25-10.fc26.i686
> > > glibc-debuginfo-2.25-12.fc26.x86_64
> > > [root@jouet perf]#
> > > 
> > > Ok, the debuginfo file is newer than the glibc installed, updating glibc
> > > now...
> > > 
> > > We could have a more informative message in this case, right? I.e.
> > > something like:
> > > 
> > > [root@jouet perf]# perf probe -l
> > > There was a build-id mismatch while trying to resolve 0xdd38eca7, please
> > > check your system's debuginfo files for mismatches, e.g. check the
> > > versions for glibc and glibc-debuginfo.
> > >   probe_libc:malloc_get_state (on 0xdd38eca7 in /usr/lib64/libc-2.25.so)
> > 
> > OK, I'll try to check how debuginfo is searched in such environment.
> 
> So, tools/perf/util/symbol.c, function dso__load(), it will have this
> loop:
> 
> 
>         /*
>          * Read the build id if possible. This is required for
>          * DSO_BINARY_TYPE__BUILDID_DEBUGINFO to work
>          */
>         if (!dso->has_build_id && is_regular_file(dso->long_name)) {
>             __symbol__join_symfs(name, PATH_MAX, dso->long_name);
>             if (filename__read_build_id(name, build_id, BUILD_ID_SIZE) > 0)
>                 dso__set_build_id(dso, build_id);
>         }
> 
>         /*
>          * Iterate over candidate debug images.
>          * Keep track of "interesting" ones (those which have a symtab, dynsym,
>          * and/or opd section) for processing.
>          */
>         for (i = 0; i < DSO_BINARY_TYPE__SYMTAB_CNT; i++) {
> 
>                 if (dso__read_binary_type_filename(dso, symtab_type, root_dir, name, PATH_MAX))
> 
> 
> -------------------
> 
> So the glibc file _has_ a build id, it reads it and then will try to
> find a file that has that build id, that 'name' variable will have
> the file being tried, which may be, for instance, at:
> 
> [acme@jouet ~]$ perf buildid-list -i /lib64/libc-2.25.so 
> 7a4787e7c1263dc25461a7b2f2abd2acaa186102
> [acme@jouet ~]$ ls -la /usr/lib/debug/.build-id/7a/4787e7c1263dc25461a7b2f2abd2acaa186102
> lrwxrwxrwx. 1 root root 33 Oct 11 09:49 /usr/lib/debug/.build-id/7a/4787e7c1263dc25461a7b2f2abd2acaa186102 -> ../../../../../lib64/libc-2.25.so
> [acme@jouet ~]$ 
> 
> etc.
> 
> So perhaps we can have a routine that does just that loop and prints the
> files it finds with the debuginfo they have to help tell which files
> where considered?

Hmm, as far as I can see, this occured in debuginfo__new(), 

struct debuginfo *debuginfo__new(const char *path)
{
        enum dso_binary_type *type;
        char buf[PATH_MAX], nil = '\0';
        struct dso *dso;
        struct debuginfo *dinfo = NULL;

        /* Try to open distro debuginfo files */
        dso = dso__new(path);
        if (!dso)
                goto out;

        for (type = distro_dwarf_types;
             !dinfo && *type != DSO_BINARY_TYPE__NOT_FOUND;
             type++) {
                if (dso__read_binary_type_filename(dso, *type, &nil,
                                                   buf, PATH_MAX) < 0)
                        continue;
                dinfo = __debuginfo__new(buf);
        }
        dso__put(dso);

out:
        /* if failed to open all distro debuginfo, open given binary */
        return dinfo ? : __debuginfo__new(path);
}

And dso__read_binary_type_filename() makes a debuginfo path
from target path but doesn't check build-id. So,
(I still can not reproduce your situation but) I guess,
dso__read_binary_type_filename() returns some path, but
__debuginfo__new() just failed to open it.
Or, __debuginfo_new() opened it but since its buildid is
different, it really failed to find any lines on given address.

> 
> But perhaps the message I suggested may be good enough?

Yeah, but this means we need to check the buildid of both
binaries.

Thank you,

> 
> - Arnaldo


-- 
Masami Hiramatsu <mhiramat@kernel.org>

[tip:perf/core] perf probe: Support escaped character in parser

[tip-bot for Masami Hiramatsu]

Commit-ID:  c588d158124d5b60184fc612e551a19720720d68
Gitweb:     https://git.kernel.org/tip/c588d158124d5b60184fc612e551a19720720d68
Author:     Masami Hiramatsu <mhiramat@kernel.org>
AuthorDate: Wed, 13 Dec 2017 00:05:12 +0900
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Wed, 27 Dec 2017 12:15:55 -0300

perf probe: Support escaped character in parser

Support the special characters escaped by '\' in parser.  This allows
user to specify versions directly like below.

  =====
  # ./perf probe -x /lib64/libc-2.25.so malloc_get_state\\@GLIBC_2.2.5
  Added new event:
    probe_libc:malloc_get_state (on malloc_get_state@GLIBC_2.2.5 in /usr/lib64/libc-2.25.so)

  You can now use it in all perf tools, such as:

	  perf record -e probe_libc:malloc_get_state -aR sleep 1

  =====

Or, you can use separators in source filename, e.g.

  =====
  # ./perf probe -x /opt/test/a.out foo+bar.c:3
  Semantic error :There is non-digit character in offset.
    Error: Command Parse Error.
  =====

Usually "+" in source file cause parser error, but

  =====
  # ./perf probe -x /opt/test/a.out foo\\+bar.c:4
  Added new event:
    probe_a:main         (on @foo+bar.c:4 in /opt/test/a.out)

  You can now use it in all perf tools, such as:

	  perf record -e probe_a:main -aR sleep 1
  =====

escaped "\+" allows you to specify that.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
Acked-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Cc: Paul Clarke <pc@us.ibm.com>
Cc: bhargavb <bhargavaramudu@gmail.com>
Cc: linux-rt-users@vger.kernel.org
Link: http://lkml.kernel.org/r/151309111236.18107.5634753157435343410.stgit@devbox
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/Documentation/perf-probe.txt | 16 +++++++++
 tools/perf/util/probe-event.c           | 58 ++++++++++++++++++++-------------
 2 files changed, 51 insertions(+), 23 deletions(-)

diff --git a/tools/perf/Documentation/perf-probe.txt b/tools/perf/Documentation/perf-probe.txt
index f963826..b6866a0 100644
--- a/tools/perf/Documentation/perf-probe.txt
+++ b/tools/perf/Documentation/perf-probe.txt
@@ -182,6 +182,14 @@ Note that before using the SDT event, the target binary (on which SDT events are
 For details of the SDT, see below.
 https://sourceware.org/gdb/onlinedocs/gdb/Static-Probe-Points.html
 
+ESCAPED CHARACTER
+-----------------
+
+In the probe syntax, '=', '@', '+', ':' and ';' are treated as a special character. You can use a backslash ('\') to escape the special characters.
+This is useful if you need to probe on a specific versioned symbols, like @GLIBC_... suffixes, or also you need to specify a source file which includes the special characters.
+Note that usually single backslash is consumed by shell, so you might need to pass double backslash (\\) or wrapping with single quotes (\'AAA\@BBB').
+See EXAMPLES how it is used.
+
 PROBE ARGUMENT
 --------------
 Each probe argument follows below syntax.
@@ -277,6 +285,14 @@ Add a USDT probe to a target process running in a different mount namespace
 
  ./perf probe --target-ns <target pid> -x /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.121-0.b13.el7_3.x86_64/jre/lib/amd64/server/libjvm.so %sdt_hotspot:thread__sleep__end
 
+Add a probe on specific versioned symbol by backslash escape
+
+ ./perf probe -x /lib64/libc-2.25.so 'malloc_get_state\@GLIBC_2.2.5'
+
+Add a probe in a source file using special characters by backslash escape
+
+ ./perf probe -x /opt/test/a.out 'foo\+bar.c:4'
+
 
 SEE ALSO
 --------
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 0d6c66d..e1dbc98 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -1325,27 +1325,30 @@ static int parse_perf_probe_event_name(char **arg, struct perf_probe_event *pev)
 {
 	char *ptr;
 
-	ptr = strchr(*arg, ':');
+	ptr = strpbrk_esc(*arg, ":");
 	if (ptr) {
 		*ptr = '\0';
 		if (!pev->sdt && !is_c_func_name(*arg))
 			goto ng_name;
-		pev->group = strdup(*arg);
+		pev->group = strdup_esc(*arg);
 		if (!pev->group)
 			return -ENOMEM;
 		*arg = ptr + 1;
 	} else
 		pev->group = NULL;
-	if (!pev->sdt && !is_c_func_name(*arg)) {
+
+	pev->event = strdup_esc(*arg);
+	if (pev->event == NULL)
+		return -ENOMEM;
+
+	if (!pev->sdt && !is_c_func_name(pev->event)) {
+		zfree(&pev->event);
 ng_name:
+		zfree(&pev->group);
 		semantic_error("%s is bad for event name -it must "
 			       "follow C symbol-naming rule.\n", *arg);
 		return -EINVAL;
 	}
-	pev->event = strdup(*arg);
-	if (pev->event == NULL)
-		return -ENOMEM;
-
 	return 0;
 }
 
@@ -1373,7 +1376,7 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
 			arg++;
 	}
 
-	ptr = strpbrk(arg, ";=@+%");
+	ptr = strpbrk_esc(arg, ";=@+%");
 	if (pev->sdt) {
 		if (ptr) {
 			if (*ptr != '@') {
@@ -1387,7 +1390,7 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
 				pev->target = build_id_cache__origname(tmp);
 				free(tmp);
 			} else
-				pev->target = strdup(ptr + 1);
+				pev->target = strdup_esc(ptr + 1);
 			if (!pev->target)
 				return -ENOMEM;
 			*ptr = '\0';
@@ -1421,13 +1424,14 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
 	 *
 	 * Otherwise, we consider arg to be a function specification.
 	 */
-	if (!strpbrk(arg, "+@%") && (ptr = strpbrk(arg, ";:")) != NULL) {
+	if (!strpbrk_esc(arg, "+@%")) {
+		ptr = strpbrk_esc(arg, ";:");
 		/* This is a file spec if it includes a '.' before ; or : */
-		if (memchr(arg, '.', ptr - arg))
+		if (ptr && memchr(arg, '.', ptr - arg))
 			file_spec = true;
 	}
 
-	ptr = strpbrk(arg, ";:+@%");
+	ptr = strpbrk_esc(arg, ";:+@%");
 	if (ptr) {
 		nc = *ptr;
 		*ptr++ = '\0';
@@ -1436,7 +1440,7 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
 	if (arg[0] == '\0')
 		tmp = NULL;
 	else {
-		tmp = strdup(arg);
+		tmp = strdup_esc(arg);
 		if (tmp == NULL)
 			return -ENOMEM;
 	}
@@ -1469,12 +1473,12 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
 		arg = ptr;
 		c = nc;
 		if (c == ';') {	/* Lazy pattern must be the last part */
-			pp->lazy_line = strdup(arg);
+			pp->lazy_line = strdup(arg); /* let leave escapes */
 			if (pp->lazy_line == NULL)
 				return -ENOMEM;
 			break;
 		}
-		ptr = strpbrk(arg, ";:+@%");
+		ptr = strpbrk_esc(arg, ";:+@%");
 		if (ptr) {
 			nc = *ptr;
 			*ptr++ = '\0';
@@ -1501,7 +1505,7 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
 				semantic_error("SRC@SRC is not allowed.\n");
 				return -EINVAL;
 			}
-			pp->file = strdup(arg);
+			pp->file = strdup_esc(arg);
 			if (pp->file == NULL)
 				return -ENOMEM;
 			break;
@@ -2803,23 +2807,31 @@ static int find_probe_functions(struct map *map, char *name,
 	struct rb_node *tmp;
 	const char *norm, *ver;
 	char *buf = NULL;
+	bool cut_version = true;
 
 	if (map__load(map) < 0)
 		return 0;
 
+	/* If user gives a version, don't cut off the version from symbols */
+	if (strchr(name, '@'))
+		cut_version = false;
+
 	map__for_each_symbol(map, sym, tmp) {
 		norm = arch__normalize_symbol_name(sym->name);
 		if (!norm)
 			continue;
 
-		/* We don't care about default symbol or not */
-		ver = strchr(norm, '@');
-		if (ver) {
-			buf = strndup(norm, ver - norm);
-			if (!buf)
-				return -ENOMEM;
-			norm = buf;
+		if (cut_version) {
+			/* We don't care about default symbol or not */
+			ver = strchr(norm, '@');
+			if (ver) {
+				buf = strndup(norm, ver - norm);
+				if (!buf)
+					return -ENOMEM;
+				norm = buf;
+			}
 		}
+
 		if (strglobmatch(norm, name)) {
 			found++;
 			if (syms && found < probe_conf.max_probes)