From 8603b6f58637ce196d68f7749633ea81af196d66 Mon Sep 17 00:00:00 2001
From: Oleksandr Natalenko <oleksandr@redhat.com>
Date: Sat, 3 Sep 2022 08:43:30 +0200
Subject: [PATCH] core_pattern: add CPU specifier
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Statistically, in a large deployment regular segfaults may indicate a CPU
issue.
Currently, it is not possible to find out what CPU the segfault happened
on. There are at least two attempts to improve segfault logging with this
regard, but they do not help in case the logs rotate.
Hence, lets make sure it is possible to permanently record a CPU the task
ran on using a new core_pattern specifier.
Link: https://lkml.kernel.org/r/20220903064330.20772-1-oleksandr@redhat.com
Signed-off-by: Oleksandr Natalenko <oleksandr@redhat.com>
Suggested-by: Renaud Métrich <rmetrich@redhat.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: Grzegorz Halat <ghalat@redhat.com>
Cc: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: Joel Savitz <jsavitz@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kees Cook <keescook@chromium.org>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Stephen Kitt <steve@sk2.org>
Cc: Will Deacon <will@kernel.org>
Cc: Xiaoming Ni <nixiaoming@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
Documentation/admin-guide/sysctl/kernel.rst | 1 +
fs/coredump.c | 5 +++++
include/linux/coredump.h | 1 +
3 files changed, 7 insertions(+)
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index 98d1b198b2b4c..3b618a4062079 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -174,6 +174,7 @@ core_pattern
%f executable filename
%E executable path
%c maximum size of core file by resource limit RLIMIT_CORE
+ %C CPU the task ran on
%<OTHER> both are dropped
======== ==========================================
diff --git a/fs/coredump.c b/fs/coredump.c
index 7bad7785e8e67..3e8630c8d6270 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -325,6 +325,10 @@ static int format_corename(struct core_name *cn, struct coredump_params *cprm,
err = cn_printf(cn, "%lu",
rlimit(RLIMIT_CORE));
break;
+ /* CPU the task ran on */
+ case 'C':
+ err = cn_printf(cn, "%d", cprm->cpu);
+ break;
default:
break;
}
@@ -534,6 +538,7 @@ void do_coredump(const kernel_siginfo_t *siginfo)
*/
.mm_flags = mm->flags,
.vma_meta = NULL,
+ .cpu = raw_smp_processor_id(),
};
audit_core_dumps(siginfo->si_signo);
diff --git a/include/linux/coredump.h b/include/linux/coredump.h
index 08a1d3e7e46d0..191dcf5af6cb9 100644
--- a/include/linux/coredump.h
+++ b/include/linux/coredump.h
@@ -22,6 +22,7 @@ struct coredump_params {
struct file *file;
unsigned long limit;
unsigned long mm_flags;
+ int cpu;
loff_t written;
loff_t pos;
loff_t to_skip;
--
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