kmsg_dump: Dump on crash_kexec as well

crash_kexec gets called before kmsg_dump(KMSG_DUMP_OOPS) if
panic_on_oops is set, so the kernel log buffer is not stored
for this case.

This patch adds a KMSG_DUMP_KEXEC dump type which gets called
when crash_kexec() is invoked. To avoid getting double dumps,
the old KMSG_DUMP_PANIC is moved below crash_kexec(). The
mtdoops driver is modified to handle KMSG_DUMP_KEXEC in the
same way as a panic.
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: NSimon Kagstrom <simon.kagstrom@netinsight.net>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/mtdoops.c

@@ -322,7 +322,7 @@ static void mtdoops_do_dump(struct kmsg_dumper *dumper,
 	memcpy(dst + l1_cpy, s2 + s2_start, l2_cpy);
 
 	/* Panics must be written immediately */
-	if (reason == KMSG_DUMP_PANIC) {
+	if (reason != KMSG_DUMP_OOPS) {
 		if (!cxt->mtd->panic_write)
 			printk(KERN_ERR "mtdoops: Cannot write from panic without panic_write\n");
 		else

include/linux/kmsg_dump.h

@@ -17,6 +17,7 @@
 enum kmsg_dump_reason {
 	KMSG_DUMP_OOPS,
 	KMSG_DUMP_PANIC,
+	KMSG_DUMP_KEXEC,
 };
 
 /**

kernel/kexec.c

@@ -32,6 +32,7 @@
 #include <linux/console.h>
 #include <linux/vmalloc.h>
 #include <linux/swap.h>
+#include <linux/kmsg_dump.h>
 
 #include <asm/page.h>
 #include <asm/uaccess.h>
@@ -1074,6 +1075,9 @@ void crash_kexec(struct pt_regs *regs)
 	if (mutex_trylock(&kexec_mutex)) {
 		if (kexec_crash_image) {
 			struct pt_regs fixed_regs;
+
+			kmsg_dump(KMSG_DUMP_KEXEC);
+
 			crash_setup_regs(&fixed_regs, regs);
 			crash_save_vmcoreinfo();
 			machine_crash_shutdown(&fixed_regs);

kernel/panic.c

@@ -75,7 +75,6 @@ NORET_TYPE void panic(const char * fmt, ...)
 	dump_stack();
 #endif
 
-	kmsg_dump(KMSG_DUMP_PANIC);
 	/*
 	 * If we have crashed and we have a crash kernel loaded let it handle
 	 * everything else.
@@ -83,6 +82,8 @@ NORET_TYPE void panic(const char * fmt, ...)
 	 */
 	crash_kexec(NULL);
 
+	kmsg_dump(KMSG_DUMP_PANIC);
+
 	/*
 	 * Note smp_send_stop is the usual smp shutdown function, which
 	 * unfortunately means it may not be hardened to work in a panic

kernel/printk.c

@@ -1467,6 +1467,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
 static const char const *kmsg_reasons[] = {
 	[KMSG_DUMP_OOPS]	= "oops",
 	[KMSG_DUMP_PANIC]	= "panic",
+	[KMSG_DUMP_KEXEC]	= "kexec",
 };
 
 static const char *kmsg_to_str(enum kmsg_dump_reason reason)