linux-kernel - [PATCH 3.16 064/148] perf probe: Fix to show function entry line as probe-able

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Message-ID: <lsq.1581185940.266564127@decadent.org.uk>
Date:   Sat, 08 Feb 2020 18:20:03 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Namhyung Kim" <namhyung@...nel.org>,
        "Masami Hiramatsu" <mhiramat@...nel.org>,
        "Arnaldo Carvalho de Melo" <acme@...hat.com>,
        "Jiri Olsa" <jolsa@...hat.com>
Subject: [PATCH 3.16 064/148] perf probe: Fix to show function entry line
 as probe-able

3.16.82-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Masami Hiramatsu <mhiramat@...nel.org>

commit 91e2f539eeda26ab00bd03fae8dc434c128c85ed upstream.

Fix die_walk_lines() to list the function entry line correctly.  Since
the dwarf_entrypc() does not return the entry pc if the DIE has only
range attribute, __die_walk_funclines() fails to list the declaration
line (entry line) in that case.

To solve this issue, this introduces die_entrypc() which correctly
returns the entry PC (the first address range) even if the DIE has only
range attribute. With this fix die_walk_lines() shows the function entry
line is able to probe correctly.

Fixes: 4cc9cec636e7 ("perf probe: Introduce lines walker interface")
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Link: http://lore.kernel.org/lkml/157190837419.1859.4619125803596816752.stgit@devnote2
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 tools/perf/util/dwarf-aux.c | 24 +++++++++++++++++++++++-
 tools/perf/util/dwarf-aux.h |  3 +++
 2 files changed, 26 insertions(+), 1 deletion(-)

--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -278,6 +278,28 @@ bool die_is_func_def(Dwarf_Die *dw_die)
 }
 
 /**
+ * die_entrypc - Returns entry PC (the lowest address) of a DIE
+ * @dw_die: a DIE
+ * @addr: where to store entry PC
+ *
+ * Since dwarf_entrypc() does not return entry PC if the DIE has only address
+ * range, we have to use this to retrieve the lowest address from the address
+ * range attribute.
+ */
+int die_entrypc(Dwarf_Die *dw_die, Dwarf_Addr *addr)
+{
+	Dwarf_Addr base, end;
+
+	if (!addr)
+		return -EINVAL;
+
+	if (dwarf_entrypc(dw_die, addr) == 0)
+		return 0;
+
+	return dwarf_ranges(dw_die, 0, &base, addr, &end) < 0 ? -ENOENT : 0;
+}
+
+/**
  * die_is_func_instance - Ensure that this DIE is an instance of a subprogram
  * @dw_die: a DIE
  *
@@ -647,7 +669,7 @@ static int __die_walk_funclines(Dwarf_Di
 	/* Handle function declaration line */
 	fname = dwarf_decl_file(sp_die);
 	if (fname && dwarf_decl_line(sp_die, &lineno) == 0 &&
-	    dwarf_entrypc(sp_die, &addr) == 0) {
+	    die_entrypc(sp_die, &addr) == 0) {
 		lw.retval = callback(fname, lineno, addr, data);
 		if (lw.retval != 0)
 			goto done;
--- a/tools/perf/util/dwarf-aux.h
+++ b/tools/perf/util/dwarf-aux.h
@@ -38,6 +38,9 @@ extern int cu_find_lineinfo(Dwarf_Die *c
 extern int cu_walk_functions_at(Dwarf_Die *cu_die, Dwarf_Addr addr,
 			int (*callback)(Dwarf_Die *, void *), void *data);
 
+/* Get the lowest PC in DIE (including range list) */
+int die_entrypc(Dwarf_Die *dw_die, Dwarf_Addr *addr);
+
 /* Ensure that this DIE is a subprogram and definition (not declaration) */
 extern bool die_is_func_def(Dwarf_Die *dw_die);