From: Stephen Boyd <swboyd@chromium.org>
To: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, Jiri Olsa <jolsa@kernel.org>,
Alexei Starovoitov <ast@kernel.org>, Jessica Yu <jeyu@kernel.org>,
Evan Green <evgreen@chromium.org>,
Hsin-Yi Wang <hsinyi@chromium.org>,
Steven Rostedt <rostedt@goodmis.org>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
linux-doc@vger.kernel.org, Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH v2 04/12] module: Add printk format to add module build ID to stacktraces
Date: Tue, 30 Mar 2021 12:12:29 -0700 [thread overview]
Message-ID: <161713154989.2260335.1975274918938126463@swboyd.mtv.corp.google.com> (raw)
In-Reply-To: <YGL9hHFg9Pm4xaNM@alley>
Quoting Petr Mladek (2021-03-30 03:29:24)
> On Tue 2021-03-23 19:04:35, Stephen Boyd wrote:
> > Let's make kernel stacktraces easier to identify by including the build
> > ID[1] of a module if the stacktrace is printing a symbol from a module.
> >
> > Example:
> >
> > WARNING: CPU: 3 PID: 3373 at drivers/misc/lkdtm/bugs.c:83 lkdtm_WARNING+0x28/0x30 [lkdtm]
> > Modules linked in: lkdtm rfcomm algif_hash algif_skcipher af_alg xt_cgroup uinput xt_MASQUERADE hci_uart <modules trimmed>
> > CPU: 3 PID: 3373 Comm: bash Not tainted 5.11 #12 a8c0d47f7051f3e6670ceaea724af66a39c6cec8
>
> I tested it with "echo l >/proc/sysrq-trigger" and I got the following
> output:
>
> [ 71.905593] CPU: 0 PID: 1762 Comm: bash Kdump: loaded Not tainted 5.12.0-rc5-default+ #167 00000080ffffffff0000000000000000
> 00000000
>
> It does not looks like an unique build-id.
> Any idea what was going wrong?
Hmm not sure. What does 'hexdump /sys/kernel/notes' show or 'file
vmlinux' parse out of the kernel image?
>
> > --- a/include/linux/kallsyms.h
> > +++ b/include/linux/kallsyms.h
> > @@ -91,6 +93,7 @@ const char *kallsyms_lookup(unsigned long addr,
> >
> > /* Look up a kernel symbol and return it in a text buffer. */
> > extern int sprint_symbol(char *buffer, unsigned long address);
> > +extern int sprint_symbol_stacktrace(char *buffer, unsigned long address);
> > extern int sprint_symbol_no_offset(char *buffer, unsigned long address);
> > extern int sprint_backtrace(char *buffer, unsigned long address);
>
> Could we use a more clear name? It is hard to guess what is
> the difference between sprint_*_stacktrace() and sprint_backtrace().
>
> What about sprint_symbol_build_id() ?
Sure.
>
>
> > diff --git a/kernel/module.c b/kernel/module.c
> > index 30479355ab85..9e9cb502fb33 100644
> > --- a/kernel/module.c
> > +++ b/kernel/module.c
> > @@ -2770,6 +2771,20 @@ static void add_kallsyms(struct module *mod, const struct load_info *info)
> > }
> > mod->core_kallsyms.num_symtab = ndst;
> > }
> > +
> > +static void init_build_id(struct module *mod, const struct load_info *info)
> > +{
> > + const Elf_Shdr *sechdr;
> > + unsigned int i;
> > +
> > + for (i = 0; i < info->hdr->e_shnum; i++) {
> > + sechdr = &info->sechdrs[i];
> > + if (!sect_empty(sechdr) && sechdr->sh_type == SHT_NOTE &&
> > + !build_id_parse_buf((void *)sechdr->sh_addr, mod->build_id,
> > + sechdr->sh_size))
> > + break;
> > + }
>
> Just to be sure. Is this really reliable way how to find the build ID,
> please?
>
The build ID is always part of a note section, so if we parse the notes
and find a build ID type of section (see nhdr->n_type == BUILD_ID) with
a GNU name then we know we have the right section and will be able to
parse the ID out of the buffer.
next prev parent reply other threads:[~2021-03-30 19:13 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-24 2:04 [PATCH v2 00/12] Add build ID to stacktraces Stephen Boyd
2021-03-24 2:04 ` [PATCH v2 01/12] buildid: Add API to parse build ID out of buffer Stephen Boyd
2021-03-24 2:04 ` [PATCH v2 02/12] buildid: Add method to get running kernel's build ID Stephen Boyd
2021-03-24 9:24 ` Rasmus Villemoes
2021-03-24 19:06 ` Stephen Boyd
2021-03-24 2:04 ` [PATCH v2 03/12] dump_stack: Add vmlinux build ID to stack traces Stephen Boyd
2021-03-24 11:22 ` Andy Shevchenko
2021-03-24 19:01 ` Stephen Boyd
2021-03-24 2:04 ` [PATCH v2 04/12] module: Add printk format to add module build ID to stacktraces Stephen Boyd
2021-03-24 9:57 ` Rasmus Villemoes
2021-03-24 19:11 ` Stephen Boyd
2021-03-24 22:21 ` Rasmus Villemoes
2021-03-24 22:28 ` Stephen Boyd
2021-03-30 10:51 ` Petr Mladek
2021-03-30 10:29 ` Petr Mladek
2021-03-30 19:12 ` Stephen Boyd [this message]
2021-03-24 2:04 ` [PATCH v2 05/12] arm64: stacktrace: Use %pSb for backtrace printing Stephen Boyd
2021-03-24 2:04 ` [PATCH v2 06/12] x86/dumpstack: " Stephen Boyd
2021-03-24 2:04 ` [PATCH v2 07/12] scripts/decode_stacktrace.sh: Support debuginfod Stephen Boyd
2021-03-24 11:27 ` Andy Shevchenko
2021-03-24 22:22 ` Stephen Boyd
2021-03-24 2:04 ` [PATCH v2 08/12] scripts/decode_stacktrace.sh: Silence stderr messages from addr2line/nm Stephen Boyd
2021-03-24 2:04 ` [PATCH v2 09/12] scripts/decode_stacktrace.sh: Indicate 'auto' can be used for base path Stephen Boyd
2021-03-24 2:04 ` [PATCH v2 10/12] buildid: Mark some arguments const Stephen Boyd
2021-03-24 2:04 ` [PATCH v2 11/12] buildid: Fix kernel-doc notation Stephen Boyd
2021-03-24 2:04 ` [PATCH v2 12/12] kdump: Use vmlinux_build_id() to simplify Stephen Boyd
2021-03-24 8:55 ` [PATCH v2 00/12] Add build ID to stacktraces Christoph Hellwig
2021-03-25 11:06 ` peter enderborg
2021-03-25 23:21 ` Stephen Boyd
2021-03-30 10:59 ` Petr Mladek
[not found] ` <32011616573677@mail.yandex-team.ru>
2021-03-24 19:04 ` Stephen Boyd
2021-03-25 11:14 ` peter enderborg
2021-03-25 23:18 ` Stephen Boyd
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