lkml.org 
[lkml]   [2021]   [Oct]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] perf symbol: ignore $a/$d symbols for ARM modules
Date
On ARM machine, kernel symbols from modules can be resolved to $a
instead of printing the actual symbol name. Ignore symbols starting with
"$" when building kallsyms rbtree.

A sample stacktrace is shown as follows:

c0f2e39c schedule_hrtimeout+0x14 ([kernel.kallsyms])
bf4a66d8 $a+0x78 ([test_module])
c0a4f5f4 kthread+0x15c ([kernel.kallsyms])
c0a001f8 ret_from_fork+0x14 ([kernel.kallsyms])

On ARM machine, $a/$d symbols are used by the compiler to mark the
beginning of code/data part in code section. These symbols are filtered
out when linking vmlinux(see scripts/kallsyms.c ignored_prefixes), but
are left on modules. So there are $a symbols in /proc/kallsyms which
share the same addresses with the actual module symbols and confuses perf
when resolving symbols.

After this patch, the module symbol name is printed:

c0f2e39c schedule_hrtimeout+0x14 ([kernel.kallsyms])
bf4a66d8 test_func+0x78 ([test_module])
c0a4f5f4 kthread+0x15c ([kernel.kallsyms])
c0a001f8 ret_from_fork+0x14 ([kernel.kallsyms])

Signed-off-by: Lexi Shao <shaolexi@huawei.com>
---
tools/perf/util/symbol.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 0fc9a5410739..35116aed74eb 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -702,6 +702,10 @@ static int map__process_kallsym_symbol(void *arg, const char *name,
if (!symbol_type__filter(type))
return 0;

+ /* Ignore local symbols for ARM modules */
+ if (name[0] == '$')
+ return 0;
+
/*
* module symbols are not sorted so we add all
* symbols, setting length to 0, and rely on
--
2.12.3
\
 
 \ /
  Last update: 2021-10-27 11:53    [W:0.081 / U:0.040 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site