[PATCH 2/3] perf probe: Support comp_dir to find an absolute source path

Masami Hiramatsu
2010-07-09T09:29:21Z

Gcc generates DW_AT_comp_dir and stores relative source path
if building kernel without O= option. In that case, perf probe
--line sometimes doesn't work without --source option, because
it tries to access relative source path.

This adds DW_AT_comp_dir support to perf probe for finding
an absolute source path when no --source option.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
---

tools/perf/util/probe-event.c | 34 ++++++++++++++++++++++------------
tools/perf/util/probe-event.h | 1 +
tools/perf/util/probe-finder.c | 21 +++++++++++++++++++++
3 files changed, 44 insertions(+), 12 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 8d08e75..4445a1e 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -201,28 +201,38 @@ static int try_to_find_kprobe_trace_events(struct perf_probe_event *pev,
* a newly allocated path on success.
* Return 0 if file was found and readable, -errno otherwise.
*/
-static int get_real_path(const char *raw_path, char **new_path)
+static int get_real_path(const char *raw_path, const char *comp_dir,
+ char **new_path)
{
- if (!symbol_conf.source_prefix) {
- if (access(raw_path, R_OK) == 0) {
- *new_path = strdup(raw_path);
- return 0;
- } else
- return -errno;
+ const char *prefix = symbol_conf.source_prefix;
+
+ if (!prefix) {
+ if (raw_path[0] != '/' && comp_dir)
+ /* If not an absolute path, try to use comp_dir */
+ prefix = comp_dir;
+ else {
+ if (access(raw_path, R_OK) == 0) {
+ *new_path = strdup(raw_path);
+ return 0;
+ } else
+ return -errno;
+ }
}

- *new_path = malloc((strlen(symbol_conf.source_prefix) +
- strlen(raw_path) + 2));
+ *new_path = malloc((strlen(prefix) + strlen(raw_path) + 2));
if (!*new_path)
return -ENOMEM;

for (;;) {
- sprintf(*new_path, "%s/%s", symbol_conf.source_prefix,
- raw_path);
+ sprintf(*new_path, "%s/%s", prefix, raw_path);

if (access(*new_path, R_OK) == 0)
return 0;

+ if (!symbol_conf.source_prefix)
+ /* In case of searching comp_dir, don't retry */
+ return -errno;
+
switch (errno) {
case ENAMETOOLONG:
case ENOENT:
@@ -318,7 +328,7 @@ int show_line_range(struct line_range *lr)

/* Convert source file path */
tmp = lr->path;
- ret = get_real_path(tmp, &lr->path);
+ ret = get_real_path(tmp, lr->comp_dir, &lr->path);
free(tmp); /* Free old path */
if (ret < 0) {
pr_warning("Failed to find source file. (%d)\n", ret);
diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
index bc06d3e..ed362ac 100644
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -86,6 +86,7 @@ struct line_range {
int end; /* End line number */
int offset; /* Start line offset */
char *path; /* Real path name */
+ char *comp_dir; /* Compile directory */
struct list_head line_list; /* Visible lines */
};

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index a934a36..37dcdb6 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -144,6 +144,15 @@ static const char *cu_find_realpath(Dwarf_Die *cu_die, const char *fname)
return src;
}

+/* Get DW_AT_comp_dir (should be NULL with older gcc) */
+static const char *cu_get_comp_dir(Dwarf_Die *cu_die)
+{
+ Dwarf_Attribute attr;
+ if (dwarf_attr(cu_die, DW_AT_comp_dir, &attr) == NULL)
+ return NULL;
+ return dwarf_formstring(&attr);
+}
+
/* Compare diename and tname */
static bool die_compare_name(Dwarf_Die *dw_die, const char *tname)
{
@@ -1374,6 +1383,7 @@ int find_line_range(int fd, struct line_range *lr)
size_t cuhl;
Dwarf_Die *diep;
Dwarf *dbg;
+ const char *comp_dir;

dbg = dwarf_begin(fd, DWARF_C_READ);
if (!dbg) {
@@ -1409,6 +1419,17 @@ int find_line_range(int fd, struct line_range *lr)
}
off = noff;
}
+
+ /* Store comp_dir */
+ if (lf.found) {
+ comp_dir = cu_get_comp_dir(&lf.cu_die);
+ if (comp_dir) {
+ lr->comp_dir = strdup(comp_dir);
+ if (!lr->comp_dir)
+ ret = -ENOMEM;
+ }
+ }
+
pr_debug("path: %s\n", lr->path);
dwarf_end(dbg);