efi: Register efi_secret platform device if EFI secret area is declared

During efi initialization, check if coco_secret is defined in the EFI
configuration table; in such case, register platform device
"efi_secret".  This allows udev to automatically load the efi_secret
module (platform driver), which in turn will populate the
<securityfs>/secrets/coco directory in guests into which secrets were
injected.

Note that a declared address of an EFI secret area doesn't mean that
secrets where indeed injected to that area; if the secret area is not
populated, the driver will not load (but the platform device will still
be registered).

Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Link: https://lore.kernel.org/r/20220412212127.154182-4-dovmurik@linux.ibm.com
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index e0f43262d451d0bb5fc6f8a3068688f50af44659..860534bcfdac2aa989f5721ec045740e94748af7 100644 (file)
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -425,6 +425,11 @@ static int __init efisubsys_init(void)
        if (efi_enabled(EFI_DBG) && efi_enabled(EFI_PRESERVE_BS_REGIONS))
                efi_debugfs_init();
 
+#ifdef CONFIG_EFI_COCO_SECRET
+       if (efi.coco_secret != EFI_INVALID_TABLE_ADDR)
+               platform_device_register_simple("efi_secret", 0, NULL, 0);
+#endif
+
        return 0;
 
 err_remove_group: