[PATCH perf/core 3/4] perf-probe: Fix --line to handle aliased symbols in glibc

[Masami Hiramatsu]

Fix perf probe --line to handle aliased symbols correctly
in glibc.

This makes line_range search failing back to address-based
alternative search as same as --add and --vars.

Without this patch;
  -----
  # ./perf probe -x /usr/lib64/libc-2.17.so -L malloc
  Specified source line is not found.
    Error: Failed to show lines.
  -----

With this patch;
  -----
  # ./perf probe -x /usr/lib64/libc-2.17.so -L malloc
  <__libc_malloc@/usr/src/debug/glibc-2.17-c758a686/malloc/malloc.c:0>
        0  __libc_malloc(size_t bytes)
        1  {
             mstate ar_ptr;
             void *victim;

             __malloc_ptr_t (*hook) (size_t, const __malloc_ptr_t)
        6      = force_reg (__malloc_hook);
        7    if (__builtin_expect (hook != NULL, 0))
        8      return (*hook)(bytes, RETURN_ADDRESS (0));

       10    arena_lookup(ar_ptr);

       12    arena_lock(ar_ptr, bytes);
  -----

Note that this actually shows __libc_malloc, since it is
the real instance of malloc. User can use both __libc_malloc
and malloc for --line.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
---
 tools/perf/util/probe-event.c |   35 +++++++++++++++++++++++++++++++++--
 1 file changed, 33 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index b8f4578..4cfd121 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -353,6 +353,31 @@ static int get_alternative_probe_event(struct debuginfo *dinfo,
 	return ret;
 }
 
+static int get_alternative_line_range(struct debuginfo *dinfo,
+				      struct line_range *lr,
+				      const char *target, bool user)
+{
+	struct perf_probe_point pp = { 0 }, result = { 0 };
+	int ret, len = 0;
+
+	pp.function = lr->function;
+	pp.file = lr->file;
+	pp.line = lr->start;
+	if (lr->end != INT_MAX)
+		len = lr->end - lr->start;
+	ret = find_alternative_probe_point(dinfo, &pp, &result,
+					   target, user);
+	if (!ret) {
+		lr->function = result.function;
+		lr->file = result.file;
+		lr->start = result.line;
+		if (lr->end != INT_MAX)
+			lr->end = lr->start + len;
+		clear_perf_probe_point(&pp);
+	}
+	return ret;
+}
+
 /* Open new debuginfo of given module */
 static struct debuginfo *open_debuginfo(const char *module, bool silent)
 {
@@ -734,7 +759,8 @@ static int _show_one_line(FILE *fp, int l, bool skip, bool show_num)
  * Show line-range always requires debuginfo to find source file and
  * line number.
  */
-static int __show_line_range(struct line_range *lr, const char *module)
+static int __show_line_range(struct line_range *lr, const char *module,
+			     bool user)
 {
 	int l = 1;
 	struct int_node *ln;
@@ -750,6 +776,11 @@ static int __show_line_range(struct line_range *lr, const char *module)
 		return -ENOENT;
 
 	ret = debuginfo__find_line_range(dinfo, lr);
+	if (!ret) {	/* Not found, retry with an alternative */
+		ret = get_alternative_line_range(dinfo, lr, module, user);
+		if (!ret)
+			ret = debuginfo__find_line_range(dinfo, lr);
+	}
 	debuginfo__delete(dinfo);
 	if (ret == 0 || ret == -ENOENT) {
 		pr_warning("Specified source line is not found.\n");
@@ -819,7 +850,7 @@ int show_line_range(struct line_range *lr, const char *module, bool user)
 	ret = init_symbol_maps(user);
 	if (ret < 0)
 		return ret;
-	ret = __show_line_range(lr, module);
+	ret = __show_line_range(lr, module, user);
 	exit_symbol_maps();
 
 	return ret;


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