From: Lexi Shao <shaolexi@huawei.com>
To: <linux-kernel@vger.kernel.org>, <linux-perf-users@vger.kernel.org>
Cc: <james.clark@arm.com>, <acme@kernel.org>,
<alexander.shishkin@linux.intel.com>, <jolsa@redhat.com>,
<mark.rutland@arm.com>, <mingo@redhat.com>, <namhyung@kernel.org>,
<nixiaoming@huawei.com>, <peterz@infradead.org>,
<qiuxi1@huawei.com>, <shaolexi@huawei.com>,
<wangbing6@huawei.com>, <jeyu@kernel.org>, <ast@kernel.org>,
<daniel@iogearbox.net>, <andrii@kernel.org>, <kafai@fb.com>,
<songliubraving@fb.com>, <yhs@fb.com>, <john.fastabend@gmail.com>,
<kpsingh@kernel.org>, <natechancellor@gmail.com>,
<ndesaulniers@google.com>, <bpf@vger.kernel.org>,
<clang-built-linux@googlegroups.com>
Subject: [PATCH v2 1/2] perf symbol: ignore $a/$d symbols for ARM modules
Date: Fri, 29 Oct 2021 14:50:37 +0800 [thread overview]
Message-ID: <20211029065038.39449-2-shaolexi@huawei.com> (raw)
In-Reply-To: <20211029065038.39449-1-shaolexi@huawei.com>
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 $a symbols in /proc/kallsyms which
share the same addresses with the actual module symbols and confuses perf
when resolving symbols.
After this patch, the module symbol name is printed:
c0f2e39c schedule_hrtimeout+0x14 ([kernel.kallsyms])
bf4a66d8 test_func+0x78 ([test_module])
c0a4f5f4 kthread+0x15c ([kernel.kallsyms])
c0a001f8 ret_from_fork+0x14 ([kernel.kallsyms])
Signed-off-by: Lexi Shao <shaolexi@huawei.com>
Reviewed-by: James Clark <james.clark@arm.com>
---
tools/perf/util/symbol.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 0fc9a5410739..35116aed74eb 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -702,6 +702,10 @@ static int map__process_kallsym_symbol(void *arg, const char *name,
if (!symbol_type__filter(type))
return 0;
+ /* Ignore local symbols for ARM modules */
+ if (name[0] == '$')
+ return 0;
+
/*
* module symbols are not sorted so we add all
* symbols, setting length to 0, and rely on
--
2.12.3
next prev parent reply other threads:[~2021-10-29 6:51 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-27 9:52 [PATCH] perf symbol: ignore $a/$d symbols for ARM modules Lexi Shao
2021-10-27 10:23 ` James Clark
2021-10-27 12:31 ` Lexi Shao
2021-10-27 15:10 ` James Clark
2021-10-28 2:05 ` Lexi Shao
2021-10-28 8:42 ` James Clark
2021-10-29 6:50 ` [PATCH v2 0/2] kallsyms: Ignore $a/$d symbols in kallsyms for ARM Lexi Shao
2021-10-29 6:50 ` Lexi Shao [this message]
2021-10-29 6:50 ` [PATCH v2 2/2] kallsyms: ignore arm mapping symbols when loading module Lexi Shao
2021-11-02 9:43 ` James Clark
2021-10-28 8:44 ` [PATCH] perf symbol: ignore $a/$d symbols for ARM modules James Clark
2021-11-06 19:48 ` Arnaldo Carvalho de Melo
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