perf probe: Fall back to debuginfod query if debuginfo and source not found locally

Since 'perf probe' heavily depends on debuginfo, debuginfod gives us
many benefits on the 'perf probe' command on remote machine.

Especially, this will be helpful for the embedded devices which will not
have enough storage, or boot with a cross-build kernel whose source code
is in the host machine.

This will work as similar to commit c7a14fdcb3fa7736 ("perf build-ids:
Fall back to debuginfod query if debuginfo not found")

Tested with:

  (host) $ cd PATH/TO/KBUILD/DIR/
  (host) $ debuginfod -F .
  ...

  (remote) # perf probe -L vfs_read
  Failed to find the path for the kernel: No such file or directory
    Error: Failed to show lines.

  (remote) # export DEBUGINFOD_URLS="http://$HOST_IP:8002/"
  (remote) # perf probe -L vfs_read
  <vfs_read@...>
        0  ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
           {
        2         ssize_t ret;

                  if (!(file->f_mode & FMODE_READ))
                          return -EBADF;
        6         if (!(file->f_mode & FMODE_CAN_READ))
                          return -EINVAL;
        8         if (unlikely(!access_ok(buf, count)))
                          return -EFAULT;

       11         ret = rw_verify_area(READ, file, pos, count);
       12         if (ret)
                          return ret;
                  if (count > MAX_RW_COUNT)
  ...

  (remote) # perf probe -a "vfs_read count"
  Added new event:
    probe:vfs_read       (on vfs_read with count)

  (remote) # perf probe -l
    probe:vfs_read       (on vfs_read@ksrc/linux/fs/read_write.c with count)

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Frank Ch. Eigler <fche@redhat.com>
Cc: Aaron Merey <amerey@redhat.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Link: http://lore.kernel.org/lkml/160041610083.912668.13659563860278615846.stgit@devnote2
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index 11be10080613..2febb5875678 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -4,6 +4,7 @@
 
 #include <stdbool.h>
 #include "intlist.h"
+#include "build-id.h"
 #include "probe-event.h"
 #include <linux/ctype.h>
 
@@ -32,6 +33,7 @@ struct debuginfo {
 	Dwfl_Module	*mod;
 	Dwfl		*dwfl;
 	Dwarf_Addr	bias;
+	const unsigned char	*build_id;
 };
 
 /* This also tries to open distro debuginfo */
@@ -59,11 +61,12 @@ int debuginfo__find_available_vars_at(struct debuginfo *dbg,
 				      struct variable_list **vls);
 
 /* Find a src file from a DWARF tag path */
-int get_real_path(const char *raw_path, const char *comp_dir,
-			 char **new_path);
+int find_source_path(const char *raw_path, const char *sbuild_id,
+		     const char *comp_dir, char **new_path);
 
 struct probe_finder {
 	struct perf_probe_event	*pev;		/* Target probe event */
+	struct debuginfo	*dbg;
 
 	/* Callback when a probe point is found */
 	int (*callback)(Dwarf_Die *sc_die, struct probe_finder *pf);