Re: [PATCH v2 5/5] perf-probe: Support escaped character in parser

[Thomas-Mich Richter]

On 12/07/2017 08:21 AM, Masami Hiramatsu wrote:
> 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@xxxxxxxxxxx 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@xxxxxxxxxx>
> ---
>  Changes in v2:
>   - Add a description and samples in Documentation/perf-probe.txt
> ---
>  tools/perf/Documentation/perf-probe.txt |   16 +++++++++
>  tools/perf/util/probe-event.c           |   54 +++++++++++++++++++------------
>  tools/perf/util/string.c                |   46 ++++++++++++++++++++++++++
>  tools/perf/util/string2.h               |    2 +
>  4 files changed, 97 insertions(+), 21 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 94acc5846e2a..c082a27982e5 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;
> @@ -2803,21 +2807,29 @@ 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);

Same as before (patch 4)

>  		if (!norm)
>  			continue;
> 
> -		/* We don't care about default symbol or not */
> -		ver = strchr(norm, '@');
> -		if (ver) {
> -			buf = strndup(norm, ver - norm);
> -			norm = buf;

Again strndup() may return a NULL ptr and then strglobmatch() / strchr() below
dereferences it.

> +		if (cut_version) {
> +			/* We don't care about default symbol or not */
> +			ver = strchr(norm, '@');
> +			if (ver) {
> +				buf = strndup(norm, ver - norm);
> +				norm = buf;
> +			}
>  		}
> +
>  		if (strglobmatch(norm, name)) {
>  			found++;
>  			if (syms && found < probe_conf.max_probes)
> diff --git a/tools/perf/util/string.c b/tools/perf/util/string.c
> index aaa08ee8c717..d8bfd0c4d2cb 100644
> --- a/tools/perf/util/string.c
> +++ b/tools/perf/util/string.c
> @@ -396,3 +396,49 @@ char *asprintf_expr_inout_ints(const char *var, bool in, size_t nints, int *ints
>  	free(expr);
>  	return NULL;
>  }
> +
> +/* Like strpbrk(), but not break if it is right after a backslash (escaped) */
> +char *strpbrk_esc(char *str, const char *stopset)
> +{
> +	char *ptr;
> +
> +	do {
> +		ptr = strpbrk(str, stopset);
> +		if (ptr == str ||
> +		    (ptr == str + 1 && *(ptr - 1) != '\\'))
> +			break;
> +		str = ptr + 1;
> +	} while (ptr && *(ptr - 1) == '\\' && *(ptr - 2) != '\\');
> +
> +	return ptr;
> +}
> +
> +/* Like strdup, but do not copy a single backslash */
> +char *strdup_esc(const char *str)
> +{
> +	char *s, *d, *p, *ret = strdup(str);
> +
> +	if (!ret)
> +		return NULL;
> +
> +	d = strchr(ret, '\\');
> +	if (!d)
> +		return ret;
> +
> +	s = d + 1;
> +	do {
> +		if (*s == '\0') {
> +			*d = '\0';
> +			break;
> +		}
> +		p = strchr(s + 1, '\\');
> +		if (p) {
> +			memmove(d, s, p - s);
> +			d += p - s;
> +			s = p + 1;
> +		} else
> +			memmove(d, s, strlen(s) + 1);
> +	} while (p);
> +
> +	return ret;
> +}
> diff --git a/tools/perf/util/string2.h b/tools/perf/util/string2.h
> index ee14ca5451ab..4c68a09b97e8 100644
> --- a/tools/perf/util/string2.h
> +++ b/tools/perf/util/string2.h
> @@ -39,5 +39,7 @@ static inline char *asprintf_expr_not_in_ints(const char *var, size_t nints, int
>  	return asprintf_expr_inout_ints(var, false, nints, ints);
>  }
> 
> +char *strpbrk_esc(char *str, const char *stopset);
> +char *strdup_esc(const char *str);
> 
>  #endif /* PERF_STRING_H */
> 
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> 


-- 
Thomas Richter, Dept 3303, IBM LTC Boeblingen Germany
--
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