linux-kernel - [PATCH] perf: unwind: fix segbase for libunwind.

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Date:	Wed, 1 Apr 2015 14:08:52 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	<acme@...nel.org>, <jolsa@...nel.org>, <namhyung@...nel.org>
CC:	<mingo@...hat.com>, <lizefan@...wei.com>, <pi3orama@....com>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH] perf: unwind: fix segbase for libunwind.

Perf passes incorrect segbase and table_data to libunwind when
map->pgoff != 0, causes unwind failure. This patch fixes this problem.

segbase is an absolute offset from the head of object file, directly
read from ELF file. Original code computes corresponding virtual address
using map->start + segbase, doesn't consider map->pgoff. Which causes
libunwind read from incorrect offset.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
---
 tools/perf/util/unwind-libunwind.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/unwind-libunwind.c b/tools/perf/util/unwind-libunwind.c
index a78c280..c2a44fe 100644
--- a/tools/perf/util/unwind-libunwind.c
+++ b/tools/perf/util/unwind-libunwind.c
@@ -342,8 +342,8 @@ find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
 		di.format   = UNW_INFO_FORMAT_REMOTE_TABLE;
 		di.start_ip = map->start;
 		di.end_ip   = map->end;
-		di.u.rti.segbase    = map->start + segbase;
-		di.u.rti.table_data = map->start + table_data;
+		di.u.rti.segbase    = map->start - map->pgoff + segbase;
+		di.u.rti.table_data = map->start - map->pgoff + table_data;
 		di.u.rti.table_len  = fde_count * sizeof(struct table_entry)
 				      / sizeof(unw_word_t);
 		return dwarf_search_unwind_table(as, ip, &di, pi,
-- 
1.8.3.4

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