linux-kernel - [BUGFIX PATCH] perf probe: Do not depend on dwfl_module

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Date:   Fri, 28 Feb 2020 00:42:01 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexandre Ghiti <alex@...ti.fr>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Sasha Levin <sashal@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Subject: [BUGFIX PATCH] perf probe: Do not depend on dwfl_module_addrsym()

Do not depend on dwfl_module_addrsym() because it can fail
on user-space shared libraries.

Actually, same bug was fixed by commit 664fee3dc379 ("perf
probe: Do not use dwfl_module_addrsym if dwarf_diename finds
symbol name"), but commit 07d369857808 ("perf probe: Fix
wrong address verification) reverted to get actual symbol
address from symtab.

This fixes it again by getting symbol address from DIE,
and only if the DIE has only address range, it uses
dwfl_module_addrsym().

Fixes: 07d369857808 ("perf probe: Fix wrong address verification)
Reported-by: Alexandre Ghiti <alex@...ti.fr>
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 tools/perf/util/probe-finder.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 1c817add6ca4..e4cff49384f4 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -637,14 +637,19 @@ static int convert_to_trace_point(Dwarf_Die *sp_die, Dwfl_Module *mod,
 		return -EINVAL;
 	}
 
-	/* Try to get actual symbol name from symtab */
-	symbol = dwfl_module_addrsym(mod, paddr, &sym, NULL);
+	if (dwarf_entrypc(sp_die, &eaddr) == 0) {
+		/* If the DIE has entrypc, use it. */
+		symbol = dwarf_diename(sp_die);
+	} else {
+		/* Try to get actual symbol name and address from symtab */
+		symbol = dwfl_module_addrsym(mod, paddr, &sym, NULL);
+		eaddr = sym.st_value;
+	}
 	if (!symbol) {
 		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;