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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@kernel.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@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/157190837419.1859.4619125803596816752.stgit@devnote2
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.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);

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