linux-kernel - [BUGFIX PATCH 1/6] perf/probe: Fix wrong address verification

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Date:   Fri, 25 Oct 2019 17:46:25 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: [BUGFIX PATCH 1/6] 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;
  # tools/perf/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
  # tools/perf/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

Reported-by: Arnaldo Carvalho de Melo <acme@...nel.org>
Fixes: 576b523721b7 ("perf probe: Fix probing symbols with optimization suffix")
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 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 cd9f95e5044e..2b6513e5725c 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);