pstore/platform: Use backend name for console registration

If the pstore backend changes, there's no indication in the logs what
the console is (it always says "pstore"). Instead, pass through the
active backend's name. (Also adjust the selftest to match.)

Link: https://lore.kernel.org/lkml/20200510202436.63222-5-keescook@chromium.org/
Link: https://lore.kernel.org/lkml/20200526135429.GQ12456@shao2-debianSigned-off-by: Kees Cook <keescook@chromium.org>

fs/pstore/platform.c

@@ -514,13 +514,15 @@ static void pstore_console_write(struct console *con, const char *s, unsigned c)
 }
 
 static struct console pstore_console = {
-	.name	= "pstore",
 	.write	= pstore_console_write,
 	.index	= -1,
 };
 
 static void pstore_register_console(void)
 {
+	/* Show which backend is going to get console writes. */
+	strscpy(pstore_console.name, psinfo->name,
+		sizeof(pstore_console.name));
 	/*
 	 * Always initialize flags here since prior unregister_console()
 	 * calls may have changed settings (specifically CON_ENABLED).

tools/testing/selftests/pstore/pstore_tests

@@ -10,7 +10,7 @@
 . ./common_tests
 
 prlog -n "Checking pstore console is registered ... "
-dmesg | grep -q "console \[pstore"
+dmesg | grep -Eq "console \[(pstore|${backend})"
 show_result $?
 
 prlog -n "Checking /dev/pmsg0 exists ... "