linux-kernel - [BUGFIX PATCH 3/4] perf probe: Fix to show calling lines of inlined functions

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Message-Id: <157241937995.32002.17899884017011512577.stgit@devnote2>
Date:   Wed, 30 Oct 2019 16:09:40 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: [BUGFIX PATCH 3/4] perf probe: Fix to show calling lines of inlined functions

Fix to show calling lines of inlined functions (where an
inline function is called).

die_walk_lines() filtered out the lines inside inlined functions
based on the address. However this also filtered out the lines
which call those inlined functions from the target function.

To solve this issue, check the call_file and call_line attributes
and do not filter out if it matches to the line information.

Without this fix, perf probe -L doesn't show some lines correctly.
(don't see the lines after 17)

  # perf probe -L vfs_read
  <vfs_read@...me/mhiramat/ksrc/linux/fs/read_write.c:0>
        0  ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
        1  {
        2         ssize_t ret;

        4         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) {
       13                 if (count > MAX_RW_COUNT)
                                  count =  MAX_RW_COUNT;
       15                 ret = __vfs_read(file, buf, count, pos);
       16                 if (ret > 0) {
                                  fsnotify_access(file);
                                  add_rchar(current, ret);
                          }

With this fix,
  # perf probe -L vfs_read
  <vfs_read@...me/mhiramat/ksrc/linux/fs/read_write.c:0>
        0  ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
        1  {
        2         ssize_t ret;

        4         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) {
       13                 if (count > MAX_RW_COUNT)
                                  count =  MAX_RW_COUNT;
       15                 ret = __vfs_read(file, buf, count, pos);
       16                 if (ret > 0) {
       17                         fsnotify_access(file);
       18                         add_rchar(current, ret);
                          }
       20                 inc_syscr(current);
                  }

Fixes: 4cc9cec636e7 ("perf probe: Introduce lines walker interface")
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 tools/perf/util/dwarf-aux.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index ac1289043204..5544bfbd0f6c 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -784,7 +784,7 @@ int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback, void *data)
 	Dwarf_Lines *lines;
 	Dwarf_Line *line;
 	Dwarf_Addr addr;
-	const char *fname, *decf = NULL;
+	const char *fname, *decf = NULL, *inf = NULL;
 	int lineno, ret = 0;
 	int decl = 0, inl;
 	Dwarf_Die die_mem, *cu_die;
@@ -835,13 +835,21 @@ int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback, void *data)
 			 */
 			if (!dwarf_haspc(rt_die, addr))
 				continue;
+
 			if (die_find_inlinefunc(rt_die, addr, &die_mem)) {
+				/* Call-site check */
+				inf = die_get_call_file(&die_mem);
+				if ((inf && !strcmp(inf, decf)) &&
+				    die_get_call_lineno(&die_mem) == lineno)
+					goto found;
+
 				dwarf_decl_line(&die_mem, &inl);
 				if (inl != decl ||
 				    decf != dwarf_decl_file(&die_mem))
 					continue;
 			}
 		}
+found:
 		/* Get source line */
 		fname = dwarf_linesrc(line, NULL, NULL);