gpt-auto-generator: automatically find the root disk of the system

When run in an initrd and no root= argument is set (or is set to
root=gpt-auto) we will automatically look for the root partition on the
same disk the EFI ESP is located on.

Since we look for swap, /home and /srv on the disk the root partition is
located on, we hence have a fully discoverable chain:

    Firmware discovers the EFI ESP partition → the initrd discovers the
    root partition → the host OS discovers swap, /home, and /srv.

Note that this requires an EFI boot loader that sets the
LoaderDevicePartUUID EFI variable, such as Gummiboot.

1 files changed, 6 insertions, 5 deletions

diff --git a/src/shared/efivars.c b/src/shared/efivars.c
index 5ee8f1eb0b..f18f5c4b16 100644
--- a/src/shared/efivars.c
+++ b/src/shared/efivars.c
@@ -440,9 +440,6 @@ int efi_loader_get_boot_usec(usec_t *firmware, usec_t *loader) {
 int efi_loader_get_device_part_uuid(sd_id128_t *u) {
         _cleanup_free_ char *p = NULL;
         int r, parsed[16];
-        unsigned i;
-
-        assert(u);
 
         r = efi_get_variable_string(EFI_VENDOR_LOADER, "LoaderDevicePartUUID", &p);
         if (r < 0)
@@ -455,8 +452,12 @@ int efi_loader_get_device_part_uuid(sd_id128_t *u) {
                    &parsed[12], &parsed[13], &parsed[14], &parsed[15]) != 16)
                 return -EIO;
 
-        for (i = 0; i < ELEMENTSOF(parsed); i++)
-                u->bytes[i] = parsed[i];
+        if (u) {
+                unsigned i;
+
+                for (i = 0; i < ELEMENTSOF(parsed); i++)
+                        u->bytes[i] = parsed[i];
+        }
 
         return 0;
 }