Commit 07d36985 authored Oct 25, 2019 by Masami Hiramatsu Committed by Arnaldo Carvalho de Melo Nov 06, 2019

perf probe: Fix wrong address verification



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: 576b5237 ("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>

parent 1785fbb7

tools/perf/util/probe-finder.c

+10 −22

Original line number	Diff line number	Diff line
		@@ -604,30 +604,18 @@ static int convert_to_trace_point(Dwarf_Die sp_die, Dwfl_Module mod,
		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);
		if (!symbol) {
		/* Try to get the symbol name from symtab */
		/* Try to get actual symbol name from symtab */
		symbol = dwfl_module_addrsym(mod, paddr, &sym, NULL);
		if (!symbol) {
		pr_warning("Failed to find symbol at 0x%lx\n",
		@@ -635,7 +623,7 @@ static int convert_to_trace_point(Dwarf_Die sp_die, Dwfl_Module mod,
		return -ENOENT;
		}
		eaddr = sym.st_value;
		}

		tp->offset = (unsigned long)(paddr - eaddr);
		tp->address = (unsigned long)paddr;
		tp->symbol = strdup(symbol);

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