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kexec: add dmesg log symbols to /proc/vmcoreinfo lists 

It would be nice to be able to extract the dmesg log from a vmcore file
without needing to keep the debug symbols for the running kernel handy all
the time.  We have a facility to do this in /proc/vmcore.  This patch adds
the log_buf and log_end symbols to the vmcoreinfo area so that tools (like
makedumpfile) can easily extract the dmesg logs from a vmcore image.

[akpm@linux-foundation.org: several fixes and cleanups]
[akpm@linux-foundation.org: fix unused log_buf_kexec_setup()]
[akpm@linux-foundation.org: build fix]
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Cc: Simon Horman <horms@verge.net.au>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Simon Horman <horms@verge.net.au>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Neil Horman 2009-04-02 16:58:57 -07:00 committed by Linus Torvalds
parent 23c36c1aec
commit 04d491ab2a
3 changed files with 24 additions and 0 deletions
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4
include/linux/kernel.h
View File

@ -242,6 +242,7 @@ extern struct ratelimit_state printk_ratelimit_state;
extern int printk_ratelimit(void);
extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
unsigned int interval_msec);
void log_buf_kexec_setup(void);
#else
static inline int vprintk(const char *s, va_list args)
__attribute__ ((format (printf, 1, 0)));
@ -253,6 +254,9 @@ static inline int printk_ratelimit(void) { return 0; }
static inline bool printk_timed_ratelimit(unsigned long *caller_jiffies, \
unsigned int interval_msec) \
{ return false; }
static inline void log_buf_kexec_setup(void)
{
}
#endif
extern int printk_needs_cpu(int cpu);

1
kernel/kexec.c
View File

@ -1409,6 +1409,7 @@ static int __init crash_save_vmcoreinfo_init(void)
VMCOREINFO_OFFSET(list_head, prev);
VMCOREINFO_OFFSET(vm_struct, addr);
VMCOREINFO_LENGTH(zone.free_area, MAX_ORDER);
log_buf_kexec_setup();
VMCOREINFO_LENGTH(free_area.free_list, MIGRATE_TYPES);
VMCOREINFO_NUMBER(NR_FREE_PAGES);
VMCOREINFO_NUMBER(PG_lru);

19
kernel/printk.c
View File

@ -32,6 +32,7 @@
#include <linux/security.h>
#include <linux/bootmem.h>
#include <linux/syscalls.h>
#include <linux/kexec.h>
#include <asm/uaccess.h>
@ -135,6 +136,24 @@ static char *log_buf = __log_buf;
static int log_buf_len = __LOG_BUF_LEN;
static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
#ifdef CONFIG_KEXEC
/*
* This appends the listed symbols to /proc/vmcoreinfo
*
* /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
* obtain access to symbols that are otherwise very difficult to locate. These
* symbols are specifically used so that utilities can access and extract the
* dmesg log from a vmcore file after a crash.
*/
void log_buf_kexec_setup(void)
{
VMCOREINFO_SYMBOL(log_buf);
VMCOREINFO_SYMBOL(log_end);
VMCOREINFO_SYMBOL(log_buf_len);
VMCOREINFO_SYMBOL(logged_chars);
}
#endif
static int __init log_buf_len_setup(char *str)
{
unsigned size = memparse(str, &str);