From: James Clark <james.clark@arm.com>
To: Lexi Shao <shaolexi@huawei.com>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: acme@kernel.org, mark.rutland@arm.com, peterz@infradead.org,
mingo@redhat.com, alexander.shishkin@linux.intel.com,
jolsa@redhat.com, namhyung@kernel.org, qiuxi1@huawei.com,
nixiaoming@huawei.com, wangbing6@huawei.com
Subject: Re: [PATCH] perf symbol: ignore $a/$d symbols for ARM modules
Date: Wed, 27 Oct 2021 11:23:57 +0100 [thread overview]
Message-ID: <1b7fa65a-7587-b7c4-2dc0-d0f389200671@arm.com> (raw)
In-Reply-To: <20211027095235.123358-1-shaolexi@huawei.com>
On 27/10/2021 10:52, Lexi Shao wrote:
> 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 $a symbols in /proc/kallsyms which
> share the same addresses with the actual module symbols and confuses perf
> when resolving symbols.
Hi Lexi,
Is it worth using or re-implementing the entire is_ignored_symbol() function
from scripts/kallsyms.c? It seems like this change only fixes one occurrence,
but is_ignored_symbol() has a big list of other cases.
Unless those cases are different?
Thanks
James
>
> After this patch, the module symbol name is printed:
>
> c0f2e39c schedule_hrtimeout+0x14 ([kernel.kallsyms])
> bf4a66d8 test_func+0x78 ([test_module])
> c0a4f5f4 kthread+0x15c ([kernel.kallsyms])
> c0a001f8 ret_from_fork+0x14 ([kernel.kallsyms])
>
> Signed-off-by: Lexi Shao <shaolexi@huawei.com>
> ---
> tools/perf/util/symbol.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index 0fc9a5410739..35116aed74eb 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -702,6 +702,10 @@ static int map__process_kallsym_symbol(void *arg, const char *name,
> if (!symbol_type__filter(type))
> return 0;
>
> + /* Ignore local symbols for ARM modules */
> + if (name[0] == '$')
> + return 0;
> +
> /*
> * module symbols are not sorted so we add all
> * symbols, setting length to 0, and rely on
>
next prev parent reply other threads:[~2021-10-27 10:24 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 [this message]
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 ` [PATCH v2 1/2] perf symbol: ignore $a/$d symbols for ARM modules Lexi Shao
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1b7fa65a-7587-b7c4-2dc0-d0f389200671@arm.com \
--to=james.clark@arm.com \
--cc=acme@kernel.org \
--cc=alexander.shishkin@linux.intel.com \
--cc=jolsa@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-perf-users@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=mingo@redhat.com \
--cc=namhyung@kernel.org \
--cc=nixiaoming@huawei.com \
--cc=peterz@infradead.org \
--cc=qiuxi1@huawei.com \
--cc=shaolexi@huawei.com \
--cc=wangbing6@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).