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kernel: printk: specify alignment for struct printk_log

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On architectures that have support for efficient unaligned access struct
printk_log has 4-byte alignment.  Specify alignment attribute in type
declaration.

The whole point of this patch is to fix deadlock which happening when
UBSAN detects unaligned access in printk() thus UBSAN recursively calls
printk() with logbuf_lock held by top printk() call.

CRs-Fixed: 969533
Change-Id: Iee822667b9104a69c3d717caeded0fcde3f6d560
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Yury Gribov <y.gribov@samsung.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kostya Serebryany <kcc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-repo: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/
Git-commit: 5c9cf8af2e77388f1da81c39237fb4f20c2f85d5
Signed-off-by: Trilok Soni <tsoni@codeaurora.org>
[satyap@codeaurora.org: trivial merge conflict resolution]
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>
This commit is contained in:
Andrey Ryabinin 2016-01-20 15:00:48 -08:00 • committed by David Keitel
parent f80aca56b9
commit bbf900d8b6
1 changed files with 5 additions and 5 deletions
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10
kernel/printk/printk.c
View file

@ -236,7 +236,11 @@ struct printk_log {
u8 facility; /* syslog facility */
u8 flags:5; /* internal record flags */
u8 level:3; /* syslog level */
};
}
#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
__packed __aligned(4)
#endif
;
/*
* The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
@ -277,11 +281,7 @@ static u32 clear_idx;
#define LOG_FACILITY(v) ((v) >> 3 & 0xff)
/* record buffer */
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
#define LOG_ALIGN 4
#else
#define LOG_ALIGN __alignof__(struct printk_log)
#endif
#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
static char *log_buf = __log_buf;