From: James Clark <james.clark@arm.com>
To: Lexi Shao <shaolexi@huawei.com>,
linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org
Cc: 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, 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: Re: [PATCH v2 2/2] kallsyms: ignore arm mapping symbols when loading module
Date: Tue, 2 Nov 2021 09:43:00 +0000 [thread overview]
Message-ID: <415161e7-cdfc-557a-23cb-f72c5829bae4@arm.com> (raw)
In-Reply-To: <20211029065038.39449-3-shaolexi@huawei.com>
On 29/10/2021 07:50, Lexi Shao wrote:
> Arm modules contains mapping symbols(e.g. $a $d) which are ignored in
> module_kallsyms_on_each_symbol. However, these symbols are still
> displayed when catting /proc/kallsyms. This confuses tools(e.g. perf)
> that resolves kernel symbols with address using information from
> /proc/kallsyms. See discussion in Link:
> https://lore.kernel.org/all/c7dfbd17-85fd-b914-b90f-082abc64c9d1@arm.com/
>
> Being left out in vmlinux(see scripts/kallsyms.c is_ignored_symbol) and
> kernelspace API implies that these symbols are not used in any cases.
> So we can ignore them in the first place by not adding them to module
> kallsyms.
>
> Signed-off-by: Lexi Shao <shaolexi@huawei.com>
I tested this and it has removed the $ symbols from kallsyms where I saw
them before.
Reviewed-by: James Clark <james.clark@arm.com>
> ---
> kernel/module.c | 19 +++++++++++--------
> 1 file changed, 11 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/module.c b/kernel/module.c
> index 5c26a76e800b..b30cbbe144c7 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2662,16 +2662,22 @@ static char elf_type(const Elf_Sym *sym, const struct load_info *info)
> return '?';
> }
>
> -static bool is_core_symbol(const Elf_Sym *src, const Elf_Shdr *sechdrs,
> - unsigned int shnum, unsigned int pcpundx)
> +static inline int is_arm_mapping_symbol(const char *str);
> +static bool is_core_symbol(const Elf_Sym *src, const struct load_info *info)
> {
> const Elf_Shdr *sec;
> + const Elf_Shdr *sechdrs = info->sechdrs;
> + unsigned int shnum = info->hdr->e_shnum;
> + unsigned int pcpundx = info->index.pcpu;
>
> if (src->st_shndx == SHN_UNDEF
> || src->st_shndx >= shnum
> || !src->st_name)
> return false;
>
> + if (is_arm_mapping_symbol(&info->strtab[src->st_name]))
> + return false;
> +
> #ifdef CONFIG_KALLSYMS_ALL
> if (src->st_shndx == pcpundx)
> return true;
> @@ -2714,8 +2720,7 @@ static void layout_symtab(struct module *mod, struct load_info *info)
> /* Compute total space required for the core symbols' strtab. */
> for (ndst = i = 0; i < nsrc; i++) {
> if (i == 0 || is_livepatch_module(mod) ||
> - is_core_symbol(src+i, info->sechdrs, info->hdr->e_shnum,
> - info->index.pcpu)) {
> + is_core_symbol(src+i, info)) {
> strtab_size += strlen(&info->strtab[src[i].st_name])+1;
> ndst++;
> }
> @@ -2778,8 +2783,7 @@ static void add_kallsyms(struct module *mod, const struct load_info *info)
> for (ndst = i = 0; i < mod->kallsyms->num_symtab; i++) {
> mod->kallsyms->typetab[i] = elf_type(src + i, info);
> if (i == 0 || is_livepatch_module(mod) ||
> - is_core_symbol(src+i, info->sechdrs, info->hdr->e_shnum,
> - info->index.pcpu)) {
> + is_core_symbol(src+i, info)) {
> mod->core_kallsyms.typetab[ndst] =
> mod->kallsyms->typetab[i];
> dst[ndst] = src[i];
> @@ -4246,8 +4250,7 @@ static const char *find_kallsyms_symbol(struct module *mod,
> * We ignore unnamed symbols: they're uninformative
> * and inserted at a whim.
> */
> - if (*kallsyms_symbol_name(kallsyms, i) == '\0'
> - || is_arm_mapping_symbol(kallsyms_symbol_name(kallsyms, i)))
> + if (*kallsyms_symbol_name(kallsyms, i) == '\0')
> continue;
>
> if (thisval <= addr && thisval > bestval) {
>
next prev parent reply other threads:[~2021-11-02 9:43 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 ` [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 [this message]
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=415161e7-cdfc-557a-23cb-f72c5829bae4@arm.com \
--to=james.clark@arm.com \
--cc=acme@kernel.org \
--cc=alexander.shishkin@linux.intel.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=clang-built-linux@googlegroups.com \
--cc=daniel@iogearbox.net \
--cc=jeyu@kernel.org \
--cc=john.fastabend@gmail.com \
--cc=jolsa@redhat.com \
--cc=kafai@fb.com \
--cc=kpsingh@kernel.org \
--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=natechancellor@gmail.com \
--cc=ndesaulniers@google.com \
--cc=nixiaoming@huawei.com \
--cc=peterz@infradead.org \
--cc=qiuxi1@huawei.com \
--cc=shaolexi@huawei.com \
--cc=songliubraving@fb.com \
--cc=wangbing6@huawei.com \
--cc=yhs@fb.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).