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Subject[PATCH perf/core ] perf probe: Show the error reason comes from invalid DSO
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Show the reason of error when dso__load* failed. This shows
when user gives wrong kernel image or wrong path.

Without this, perf probe shows an obscure message.
----
$ perf probe -k ~/kbin/linux-3.x86_64/vmlinux -L vfs_read
Failed to find path of kernel module.
Error: Failed to show lines.
----

With this, perf shows appropriate error message.
----
$ perf probe -k ~/kbin/linux-3.x86_64/vmlinux -L vfs_read
Failed to find the path for kernel: Mismatching build id
Error: Failed to show lines.
----
And
----
$ perf probe -k /non-exist/kernel/vmlinux -L vfs_read
Failed to find the path for kernel: No such file or directory
Error: Failed to show lines.
----

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
---
tools/perf/util/probe-event.c | 47 +++++++++++++++++++++--------------------
tools/perf/util/probe-event.h | 3 ---
2 files changed, 24 insertions(+), 26 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index a2d8cef..a4830a6 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -201,11 +201,12 @@ static void put_target_map(struct map *map, bool user)
}


-static struct dso *kernel_get_module_dso(const char *module)
+static int kernel_get_module_dso(const char *module, struct dso **pdso)
{
struct dso *dso;
struct map *map;
const char *vmlinux_name;
+ int ret = 0;

if (module) {
list_for_each_entry(dso, &host_machine->kernel_dsos.head,
@@ -215,30 +216,21 @@ static struct dso *kernel_get_module_dso(const char *module)
goto found;
}
pr_debug("Failed to find module %s.\n", module);
- return NULL;
+ return -ENOENT;
}

map = host_machine->vmlinux_maps[MAP__FUNCTION];
dso = map->dso;

vmlinux_name = symbol_conf.vmlinux_name;
- if (vmlinux_name) {
- if (dso__load_vmlinux(dso, map, vmlinux_name, false, NULL) <= 0)
- return NULL;
- } else {
- if (dso__load_vmlinux_path(dso, map, NULL) <= 0) {
- pr_debug("Failed to load kernel map.\n");
- return NULL;
- }
- }
+ dso->load_errno = 0;
+ if (vmlinux_name)
+ ret = dso__load_vmlinux(dso, map, vmlinux_name, false, NULL);
+ else
+ ret = dso__load_vmlinux_path(dso, map, NULL);
found:
- return dso;
-}
-
-const char *kernel_get_module_path(const char *module)
-{
- struct dso *dso = kernel_get_module_dso(module);
- return (dso) ? dso->long_name : NULL;
+ *pdso = dso;
+ return ret;
}

static int convert_exec_to_group(const char *exec, char **result)
@@ -390,16 +382,25 @@ static int get_alternative_line_range(struct debuginfo *dinfo,
static struct debuginfo *open_debuginfo(const char *module, bool silent)
{
const char *path = module;
- struct debuginfo *ret;
+ char reason[STRERR_BUFSIZE];
+ struct debuginfo *ret = NULL;
+ struct dso *dso = NULL;
+ int err;

if (!module || !strchr(module, '/')) {
- path = kernel_get_module_path(module);
- if (!path) {
+ err = kernel_get_module_dso(module, &dso);
+ if (err < 0) {
+ if (!dso || dso->load_errno == 0) {
+ if (!strerror_r(-err, reason, STRERR_BUFSIZE))
+ strcpy(reason, "(unknown)");
+ } else
+ dso__strerror_load(dso, reason, STRERR_BUFSIZE);
if (!silent)
- pr_err("Failed to find path of %s module.\n",
- module ?: "kernel");
+ pr_err("Failed to find the path for %s: %s\n",
+ module ?: "kernel", reason);
return NULL;
}
+ path = dso->long_name;
}
ret = debuginfo__new(path);
if (!ret && !silent) {
diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
index 537eb32..31db6ee 100644
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -131,9 +131,6 @@ extern void line_range__clear(struct line_range *lr);
/* Initialize line range */
extern int line_range__init(struct line_range *lr);

-/* Internal use: Return kernel/module path */
-extern const char *kernel_get_module_path(const char *module);
-
extern int add_perf_probe_events(struct perf_probe_event *pevs, int npevs);
extern int del_perf_probe_events(struct strfilter *filter);
extern int show_perf_probe_events(struct strfilter *filter);


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