[PATCH 3.16 059/148] perf probe: Fix to handle optimized not-inlined functions

Ben Hutchings
2020-02-08T18:31:39Z

From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

commit e1ecbbc3fa834cc6b4b344edb1968e734d57189b upstream.

Fix to handle optimized no-inline functions which have only function
definition but no actual instance at that point.

To fix this problem, we need to find actual instance of the function.

Without this patch:
----
# perf probe -a __up
Failed to get entry address of __up.
Error: Failed to add events.
# perf probe -L __up
Specified source line is not found.
Error: Failed to show lines.
----

With this patch:
----
# perf probe -a __up
Added new event:
probe:__up (on __up)

You can now use it in all perf tools, such as:

perf record -e probe:__up -aR sleep 1

# perf probe -L __up
<__up@/home/fedora/ksrc/linux-3/kernel/locking/semaphore.c:0>
0 static noinline void __sched __up(struct semaphore *sem)
{
struct semaphore_waiter *waiter = list_first_entry(&sem->wait_
struct semaphore_waite
4 list_del(&waiter->list);
5 waiter->up = true;
6 wake_up_process(waiter->task);
7 }
----

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20150130093744.30575.43290.stgit@localhost.localdomain
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 | 15 +++++++++++++++
tools/perf/util/dwarf-aux.h | 3 +++
tools/perf/util/probe-finder.c | 12 ++++--------
3 files changed, 22 insertions(+), 8 deletions(-)

--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -278,6 +278,21 @@ bool die_is_func_def(Dwarf_Die *dw_die)
}

/**
+ * die_is_func_instance - Ensure that this DIE is an instance of a subprogram
+ * @dw_die: a DIE
+ *
+ * Ensure that this DIE is an instance (which has an entry address).
+ * This returns true if @dw_die is a function instance. If not, you need to
+ * call die_walk_instances() to find actual instances.
+ **/
+bool die_is_func_instance(Dwarf_Die *dw_die)
+{
+ Dwarf_Addr tmp;
+
+ /* Actually gcc optimizes non-inline as like as inlined */
+ return !dwarf_func_inline(dw_die) && dwarf_entrypc(dw_die, &tmp) == 0;
+}
+/**
* die_get_data_member_location - Get the data-member offset
* @mb_die: a DIE of a member of a data structure
* @offs: The offset of the member in the data structure
--- a/tools/perf/util/dwarf-aux.h
+++ b/tools/perf/util/dwarf-aux.h
@@ -41,6 +41,9 @@ extern int cu_walk_functions_at(Dwarf_Di
/* Ensure that this DIE is a subprogram and definition (not declaration) */
extern bool die_is_func_def(Dwarf_Die *dw_die);

+/* Ensure that this DIE is an instance of a subprogram */
+extern bool die_is_func_instance(Dwarf_Die *dw_die);
+
/* Compare diename and tname */
extern bool die_compare_name(Dwarf_Die *dw_die, const char *tname);

--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -909,17 +909,13 @@ static int probe_point_search_cb(Dwarf_D
dwarf_decl_line(sp_die, &pf->lno);
pf->lno += pp->line;
param->retval = find_probe_point_by_line(pf);
- } else if (!dwarf_func_inline(sp_die)) {
+ } else if (die_is_func_instance(sp_die)) {
+ /* Instances always have the entry address */
+ dwarf_entrypc(sp_die, &pf->addr);
/* Real function */
if (pp->lazy_line)
param->retval = find_probe_point_lazy(sp_die, pf);
else {
- if (dwarf_entrypc(sp_die, &pf->addr) != 0) {
- pr_warning("Failed to get entry address of "
- "%s.\n", dwarf_diename(sp_die));
- param->retval = -ENOENT;
- return DWARF_CB_ABORT;
- }
pf->addr += pp->offset;
/* TODO: Check the address in this function */
param->retval = call_probe_finder(sp_die, pf);
@@ -1514,7 +1510,7 @@ static int line_range_search_cb(Dwarf_Di
pr_debug("New line range: %d to %d\n", lf->lno_s, lf->lno_e);
lr->start = lf->lno_s;
lr->end = lf->lno_e;
- if (dwarf_func_inline(sp_die))
+ if (!die_is_func_instance(sp_die))
param->retval = die_walk_instances(sp_die,
line_range_inline_cb, lf);
else