[PATCH] Kdump: Export crash notes section address through sysfs

o Following patch exports kexec global variable "crash_notes" to user space
through sysfs as kernel attribute in /sys/kernel.

Signed-off-by: Maneesh Soni <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/i386/kernel/crash.c

···
 #include <asm/apic.h>
 #include <mach_ipi.h>
 
-#define MAX_NOTE_BYTES 1024
-typedef u32 note_buf_t[MAX_NOTE_BYTES/4];
 
 note_buf_t crash_notes[NR_CPUS];
 

arch/x86_64/kernel/crash.c

···
 #include <asm/nmi.h>
 #include <asm/hw_irq.h>
 
-#define MAX_NOTE_BYTES 1024
-typedef u32 note_buf_t[MAX_NOTE_BYTES/4];
-
 note_buf_t crash_notes[NR_CPUS];
 
 void machine_crash_shutdown(void)

include/asm-i386/kexec.h

···
 /* The native architecture */
 #define KEXEC_ARCH KEXEC_ARCH_386
 
+#define MAX_NOTE_BYTES 1024
+typedef u32 note_buf_t[MAX_NOTE_BYTES/4];
+
+extern note_buf_t crash_notes[];
+
 #endif /* _I386_KEXEC_H */

include/asm-x86_64/kexec.h

···
 /* The native architecture */
 #define KEXEC_ARCH KEXEC_ARCH_X86_64
 
+#define MAX_NOTE_BYTES 1024
+typedef u32 note_buf_t[MAX_NOTE_BYTES/4];
+
+extern note_buf_t crash_notes[];
+
 #endif /* _X86_64_KEXEC_H */

kernel/ksysfs.c

···
 KERNEL_ATTR_RO(hotplug_seqnum);
 #endif
 
+#ifdef CONFIG_KEXEC
+#include <asm/kexec.h>
+
+static ssize_t crash_notes_show(struct subsystem *subsys, char *page)
+{
+	return sprintf(page, "%p\n", (void *)crash_notes);
+}
+KERNEL_ATTR_RO(crash_notes);
+#endif
+
 decl_subsys(kernel, NULL, NULL);
 EXPORT_SYMBOL_GPL(kernel_subsys);
 
 static struct attribute * kernel_attrs[] = {
 #ifdef CONFIG_HOTPLUG
 	&hotplug_seqnum_attr.attr,
+#endif
+#ifdef CONFIG_KEXEC
+	&crash_notes_attr.attr,
 #endif
 	NULL
 };