linux-kernel - [PATCH v10 3/4] efi: Register efi_secret platform device if EFI secret area is declared

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Message-Id: <20220412212127.154182-4-dovmurik@linux.ibm.com>
Date:   Tue, 12 Apr 2022 21:21:26 +0000
From:   Dov Murik <dovmurik@...ux.ibm.com>
To:     linux-efi@...r.kernel.org
Cc:     Dov Murik <dovmurik@...ux.ibm.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Borislav Petkov <bp@...e.de>,
        Ashish Kalra <ashish.kalra@....com>,
        Brijesh Singh <brijesh.singh@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Andrew Scull <ascull@...gle.com>,
        Dave Hansen <dave.hansen@...el.com>,
        "Dr. David Alan Gilbert" <dgilbert@...hat.com>,
        Lenny Szubowicz <lszubowi@...hat.com>,
        Peter Gonda <pgonda@...gle.com>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        James Bottomley <jejb@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@...ux.ibm.com>,
        Jim Cadden <jcadden@....com>,
        Daniele Buono <dbuono@...ux.vnet.ibm.com>,
        linux-coco@...ts.linux.dev, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v10 3/4] 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@...ux.ibm.com>
Reviewed-by: Gerd Hoffmann <kraxel@...hat.com>
---
 drivers/firmware/efi/efi.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 378d044b2463..b8e68a121119 100644
--- 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:
-- 
2.25.1