[PATCH 5.4 215/222] perf probe: Fix wrong address verification

Greg Kroah-Hartman
2020-01-22T13:27:58Z

From: Masami Hiramatsu <mhiramat@kernel.org>

commit 07d369857808b7e8e471bbbbb0074a6718f89b31 upstream.

Since there are some DIE which has only ranges instead of the
combination of entrypc/highpc, address verification must use
dwarf_haspc() instead of dwarf_entrypc/dwarf_highpc.

Also, the ranges only DIE will have a partial code in different section
(e.g. unlikely code will be in text.unlikely as "FUNC.cold" symbol). In
that case, we can not use dwarf_entrypc() or die_entrypc(), because the
offset from original DIE can be a minus value.

Instead, this simply gets the symbol and offset from symtab.

Without this patch;

# perf probe -D clear_tasks_mm_cpumask:1
Failed to get entry address of clear_tasks_mm_cpumask
Error: Failed to add events.

And with this patch:

# perf probe -D clear_tasks_mm_cpumask:1
p:probe/clear_tasks_mm_cpumask clear_tasks_mm_cpumask+0
p:probe/clear_tasks_mm_cpumask_1 clear_tasks_mm_cpumask+5
p:probe/clear_tasks_mm_cpumask_2 clear_tasks_mm_cpumask+8
p:probe/clear_tasks_mm_cpumask_3 clear_tasks_mm_cpumask+16
p:probe/clear_tasks_mm_cpumask_4 clear_tasks_mm_cpumask+82

Committer testing:

I managed to reproduce the above:

[root@quaco ~]# perf probe -D clear_tasks_mm_cpumask:1
p:probe/clear_tasks_mm_cpumask _text+919968
p:probe/clear_tasks_mm_cpumask_1 _text+919973
p:probe/clear_tasks_mm_cpumask_2 _text+919976
[root@quaco ~]#

But then when trying to actually put the probe in place, it fails if I
use :0 as the offset:

[root@quaco ~]# perf probe -L clear_tasks_mm_cpumask | head -5
<clear_tasks_mm_cpumask@/usr/src/debug/kernel-5.2.fc30/linux-5.2.18-200.fc30.x86_64/kernel/cpu.c:0>
0 void clear_tasks_mm_cpumask(int cpu)
1 {
2 struct task_struct *p;

[root@quaco ~]# perf probe clear_tasks_mm_cpumask:0
Probe point 'clear_tasks_mm_cpumask' not found.
Error: Failed to add events.
[root@quaco

The next patch is needed to fix this case.

Fixes: 576b523721b7 ("perf probe: Fix probing symbols with optimization suffix")
Reported-by: Arnaldo Carvalho de Melo <acme@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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/157199318513.8075.10463906803299647907.stgit@devnote2
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
tools/perf/util/probe-finder.c | 32 ++++++++++----------------------
1 file changed, 10 insertions(+), 22 deletions(-)

--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -604,38 +604,26 @@ static int convert_to_trace_point(Dwarf_
const char *function,
struct probe_trace_point *tp)
{
- Dwarf_Addr eaddr, highaddr;
+ Dwarf_Addr eaddr;
GElf_Sym sym;
const char *symbol;

/* Verify the address is correct */
- if (dwarf_entrypc(sp_die, &eaddr) != 0) {
- pr_warning("Failed to get entry address of %s\n",
- dwarf_diename(sp_die));
- return -ENOENT;
- }
- if (dwarf_highpc(sp_die, &highaddr) != 0) {
- pr_warning("Failed to get end address of %s\n",
- dwarf_diename(sp_die));
- return -ENOENT;
- }
- if (paddr > highaddr) {
- pr_warning("Offset specified is greater than size of %s\n",
+ if (!dwarf_haspc(sp_die, paddr)) {
+ pr_warning("Specified offset is out of %s\n",
dwarf_diename(sp_die));
return -EINVAL;
}

- symbol = dwarf_diename(sp_die);
+ /* Try to get actual symbol name from symtab */
+ symbol = dwfl_module_addrsym(mod, paddr, &sym, NULL);
if (!symbol) {
- /* Try to get the symbol name from symtab */
- symbol = dwfl_module_addrsym(mod, paddr, &sym, NULL);
- if (!symbol) {
- pr_warning("Failed to find symbol at 0x%lx\n",
- (unsigned long)paddr);
- return -ENOENT;
- }
- eaddr = sym.st_value;
+ pr_warning("Failed to find symbol at 0x%lx\n",
+ (unsigned long)paddr);
+ return -ENOENT;
}
+ eaddr = sym.st_value;
+
tp->offset = (unsigned long)(paddr - eaddr);
tp->address = (unsigned long)paddr;
tp->symbol = strdup(symbol);