linux-kernel - [tip: perf/core] perf probe: Fix wrong address verification

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Message-ID: <157355749105.29376.15812882742854411341.tip-bot2@tip-bot2>
Date:   Tue, 12 Nov 2019 11:18:11 -0000
From:   "tip-bot2 for Masami Hiramatsu" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        linux-kernel@...r.kernel.org
Subject: [tip: perf/core] perf probe: Fix wrong address verification

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     07d369857808b7e8e471bbbbb0074a6718f89b31
Gitweb:        https://git.kernel.org/tip/07d369857808b7e8e471bbbbb0074a6718f89b31
Author:        Masami Hiramatsu <mhiramat@...nel.org>
AuthorDate:    Fri, 25 Oct 2019 17:46:25 +09:00
Committer:     Arnaldo Carvalho de Melo <acme@...hat.com>
CommitterDate: Wed, 06 Nov 2019 15:43:06 -03:00

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@...co ~]# 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@...co ~]#

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

  [root@...co ~]# perf probe -L clear_tasks_mm_cpumask | head -5
  <clear_tasks_mm_cpumask@...r/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@...co ~]# perf probe clear_tasks_mm_cpumask:0
  Probe point 'clear_tasks_mm_cpumask' not found.
    Error: Failed to add events.
  [root@...co

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@...nel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
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/157199318513.8075.10463906803299647907.stgit@devnote2
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/probe-finder.c | 32 ++++++++++----------------------
 1 file changed, 10 insertions(+), 22 deletions(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index cd9f95e..2b6513e 100644
--- 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_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);
+	/* 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);