linux-kernel - [PATCH v8 15/15] x86: EFI stub DRTM launch support for Secure Launch

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Date: Wed, 14 Feb 2024 14:18:47 -0800
From: Ross Philipson <ross.philipson@...cle.com>
To: linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-integrity@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-crypto@...r.kernel.org, kexec@...ts.infradead.org,
        linux-efi@...r.kernel.org
Cc: ross.philipson@...cle.com, dpsmith@...rtussolutions.com,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        dave.hansen@...ux.intel.com, ardb@...nel.org, mjg59@...f.ucam.org,
        James.Bottomley@...senpartnership.com, peterhuewe@....de,
        jarkko@...nel.org, jgg@...pe.ca, luto@...capital.net,
        nivedita@...m.mit.edu, herbert@...dor.apana.org.au,
        davem@...emloft.net, kanth.ghatraju@...cle.com,
        trenchboot-devel@...glegroups.com
Subject: [PATCH v8 15/15] x86: EFI stub DRTM launch support for Secure Launch

This support allows the DRTM launch to be initiated after an EFI stub
launch of the Linux kernel is done. This is accomplished by providing
a handler to jump to when a Secure Launch is in progress. This has to be
called after the EFI stub does Exit Boot Services.

Signed-off-by: Ross Philipson <ross.philipson@...cle.com>
---
 drivers/firmware/efi/libstub/x86-stub.c | 55 +++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index 0d510c9a06a4..4df2cf539194 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -9,6 +9,7 @@
 #include <linux/efi.h>
 #include <linux/pci.h>
 #include <linux/stddef.h>
+#include <linux/slr_table.h>
 
 #include <asm/efi.h>
 #include <asm/e820/types.h>
@@ -810,6 +811,57 @@ static efi_status_t efi_decompress_kernel(unsigned long *kernel_entry)
 	return EFI_SUCCESS;
 }
 
+static void efi_secure_launch(struct boot_params *boot_params)
+{
+	struct slr_entry_uefi_config *uefi_config;
+	struct slr_uefi_cfg_entry *uefi_entry;
+	struct slr_entry_dl_info *dlinfo;
+	efi_guid_t guid = SLR_TABLE_GUID;
+	struct slr_table *slrt;
+	u64 memmap_hi;
+	void *table;
+	u8 buf[64] = {0};
+
+	table = get_efi_config_table(guid);
+
+	/*
+	 * The presence of this table indicated a Secure Launch
+	 * is being requested.
+	 */
+	if (!table)
+		return;
+
+	slrt = (struct slr_table *)table;
+
+	if (slrt->magic != SLR_TABLE_MAGIC)
+		return;
+
+	/* Add config information to measure the UEFI memory map */
+	uefi_config = (struct slr_entry_uefi_config *)buf;
+	uefi_config->hdr.tag = SLR_ENTRY_UEFI_CONFIG;
+	uefi_config->hdr.size = sizeof(*uefi_config) + sizeof(*uefi_entry);
+	uefi_config->revision = SLR_UEFI_CONFIG_REVISION;
+	uefi_config->nr_entries = 1;
+	uefi_entry = (struct slr_uefi_cfg_entry *)(buf + sizeof(*uefi_config));
+	uefi_entry->pcr = 18;
+	uefi_entry->cfg = boot_params->efi_info.efi_memmap;
+	memmap_hi = boot_params->efi_info.efi_memmap_hi;
+	uefi_entry->cfg |= memmap_hi << 32;
+	uefi_entry->size = boot_params->efi_info.efi_memmap_size;
+	memcpy(&uefi_entry->evt_info[0], "Measured UEFI memory map",
+		strlen("Measured UEFI memory map"));
+
+	if (slr_add_entry(slrt, (struct slr_entry_hdr *)uefi_config))
+		return;
+
+	/* Jump through DL stub to initiate Secure Launch */
+	dlinfo = (struct slr_entry_dl_info *)
+		slr_next_entry_by_tag(slrt, NULL, SLR_ENTRY_DL_INFO);
+
+	asm volatile ("jmp *%%rax"
+		      : : "a" (dlinfo->dl_handler), "D" (&dlinfo->bl_context));
+}
+
 static void __noreturn enter_kernel(unsigned long kernel_addr,
 				    struct boot_params *boot_params)
 {
@@ -934,6 +986,9 @@ void __noreturn efi_stub_entry(efi_handle_t handle,
 		goto fail;
 	}
 
+	/* If a Secure Launch is in progress, this never returns */
+	efi_secure_launch(boot_params);
+
 	/*
 	 * Call the SEV init code while still running with the firmware's
 	 * GDT/IDT, so #VC exceptions will be handled by EFI.
-- 
2.39.3