Commit 04d491ab authored by Neil Horman's avatar Neil Horman Committed by Linus Torvalds
Browse files

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: default avatarNeil Horman <nhorman@tuxdriver.com>
Cc: Simon Horman <horms@verge.net.au>
Acked-by: default avatarVivek 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 23c36c1a

include/linux/kernel.h

+4 −0
Original line number Diff line number Diff line
@@ -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);

kernel/kexec.c

+1 −0
Original line number Diff line number Diff line
@@ -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);

kernel/printk.c

+19 −0
Original line number Diff line number Diff line
@@ -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);

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