printk: Collapse shutdown types into a single dump reason

To turn the KMSG_DUMP_* reasons into a more ordered list, collapse
the redundant KMSG_DUMP_(RESTART|HALT|POWEROFF) reasons into
KMSG_DUMP_SHUTDOWN. The current users already don't meaningfully
distinguish between them, so there's no need to, as discussed here:
https://lore.kernel.org/lkml/CA+CK2bAPv5u1ih5y9t5FUnTyximtFCtDYXJCpuyjOyHNOkRdqw@mail.gmail.com/

Link: https://lore.kernel.org/lkml/20200515184434.8470-2-keescook@chromium.org/
Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Signed-off-by: Kees Cook <keescook@chromium.org>

arch/powerpc/kernel/nvram_64.c

@@ -668,9 +668,7 @@ static void oops_to_nvram(struct kmsg_dumper *dumper,
 	int rc = -1;
 
 	switch (reason) {
-	case KMSG_DUMP_RESTART:
-	case KMSG_DUMP_HALT:
-	case KMSG_DUMP_POWEROFF:
+	case KMSG_DUMP_SHUTDOWN:
 		/* These are almost always orderly shutdowns. */
 		return;
 	case KMSG_DUMP_OOPS:

fs/pstore/platform.c

@@ -118,12 +118,8 @@ static const char *get_reason_str(enum kmsg_dump_reason reason)
 		return "Oops";
 	case KMSG_DUMP_EMERG:
 		return "Emergency";
-	case KMSG_DUMP_RESTART:
-		return "Restart";
-	case KMSG_DUMP_HALT:
-		return "Halt";
-	case KMSG_DUMP_POWEROFF:
-		return "Poweroff";
+	case KMSG_DUMP_SHUTDOWN:
+		return "Shutdown";
 	default:
 		return "Unknown";
 	}

include/linux/kmsg_dump.h

@@ -25,9 +25,7 @@ enum kmsg_dump_reason {
 	KMSG_DUMP_PANIC,
 	KMSG_DUMP_OOPS,
 	KMSG_DUMP_EMERG,
-	KMSG_DUMP_RESTART,
-	KMSG_DUMP_HALT,
-	KMSG_DUMP_POWEROFF,
+	KMSG_DUMP_SHUTDOWN,
 };
 
 /**

kernel/reboot.c

@@ -223,7 +223,7 @@ void kernel_restart(char *cmd)
 		pr_emerg("Restarting system\n");
 	else
 		pr_emerg("Restarting system with command '%s'\n", cmd);
-	kmsg_dump(KMSG_DUMP_RESTART);
+	kmsg_dump(KMSG_DUMP_SHUTDOWN);
 	machine_restart(cmd);
 }
 EXPORT_SYMBOL_GPL(kernel_restart);
@@ -249,7 +249,7 @@ void kernel_halt(void)
 	migrate_to_reboot_cpu();
 	syscore_shutdown();
 	pr_emerg("System halted\n");
-	kmsg_dump(KMSG_DUMP_HALT);
+	kmsg_dump(KMSG_DUMP_SHUTDOWN);
 	machine_halt();
 }
 EXPORT_SYMBOL_GPL(kernel_halt);
@@ -267,7 +267,7 @@ void kernel_power_off(void)
 	migrate_to_reboot_cpu();
 	syscore_shutdown();
 	pr_emerg("Power down\n");
-	kmsg_dump(KMSG_DUMP_POWEROFF);
+	kmsg_dump(KMSG_DUMP_SHUTDOWN);
 	machine_power_off();
 }
 EXPORT_SYMBOL_GPL(kernel_power_off);