linux-kernel - [PATCH v6 2/5] efi/libstub: Reserve confidential computing secret area

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Message-Id: <20211129114251.3741721-3-dovmurik@linux.ibm.com>
Date:   Mon, 29 Nov 2021 11:42:48 +0000
From:   Dov Murik <dovmurik@...ux.ibm.com>
To:     linux-efi@...r.kernel.org
Cc:     Dov Murik <dovmurik@...ux.ibm.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>,
        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 v6 2/5] efi/libstub: Reserve confidential computing secret area

Some older firmware declare the confidential computing secret area as
EFI_BOOT_SERVICES_DATA region.  Fix this up by treating this memory
region as EFI_RESERVED_TYPE, as it should be.

If that memory region is already EFI_RESERVED_TYPE then this has no
effect on the E820 map.

Signed-off-by: Dov Murik <dovmurik@...ux.ibm.com>
---
 drivers/firmware/efi/libstub/x86-stub.c | 28 +++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index f14c4ff5839f..dabfa33ae2b3 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -24,6 +24,7 @@
 const efi_system_table_t *efi_system_table;
 extern u32 image_offset;
 static efi_loaded_image_t *image = NULL;
+static u64 efi_coco_secret_phys_addr = U64_MAX;
 
 static efi_status_t
 preserve_pci_rom_image(efi_pci_io_protocol_t *pci, struct pci_setup_rom **__rom)
@@ -443,6 +444,21 @@ static void add_e820ext(struct boot_params *params,
 		params->hdr.setup_data = (unsigned long)e820ext;
 }
 
+#ifdef CONFIG_EFI_COCO_SECRET
+static void efi_set_coco_secret_phys_addr(void)
+{
+	struct linux_efi_coco_secret_area *secret_area =
+		get_efi_config_table(LINUX_EFI_COCO_SECRET_AREA_GUID);
+
+	if (!secret_area || secret_area->size == 0 || secret_area->size >= SZ_4G)
+		return;
+
+	efi_coco_secret_phys_addr = secret_area->base_pa;
+}
+#else
+static void efi_set_coco_secret_phys_addr(void) {}
+#endif
+
 static efi_status_t
 setup_e820(struct boot_params *params, struct setup_data *e820ext, u32 e820ext_size)
 {
@@ -494,6 +510,16 @@ setup_e820(struct boot_params *params, struct setup_data *e820ext, u32 e820ext_s
 				e820_type = E820_TYPE_SOFT_RESERVED;
 			else
 				e820_type = E820_TYPE_RAM;
+#ifdef CONFIG_EFI_COCO_SECRET
+			if (d->phys_addr == efi_coco_secret_phys_addr)
+				/*
+				 * Fix a quirk in firmwares which don't mark
+				 * the EFI confidential computing area as
+				 * EFI_RESERVED_TYPE, but instead as
+				 * EFI_BOOT_SERVICES_DATA.
+				 */
+				e820_type = E820_TYPE_RESERVED;
+#endif
 			break;
 
 		case EFI_ACPI_MEMORY_NVS:
@@ -793,6 +819,8 @@ unsigned long efi_main(efi_handle_t handle,
 
 	efi_retrieve_tpm2_eventlog();
 
+	efi_set_coco_secret_phys_addr();
+
 	setup_graphics(boot_params);
 
 	setup_efi_pci(boot_params);
-- 
2.25.1