x86/efi: 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@oracle.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>

Author: rossphilipson

drivers/firmware/efi/libstub/efistub.h

@@ -135,6 +135,14 @@ void efi_set_u64_split(u64 data, u32 *lo, u32 *hi)
 	*hi = upper_32_bits(data);
 }
 
+static inline
+void efi_set_u64_form(u32 lo, u32 hi, u64 *data)
+{
+	u64 upper = hi;
+
+	*data = lo | upper << 32;
+}
+
 /*
  * Allocation types for calls to boottime->allocate_pages.
  */

drivers/firmware/efi/libstub/x86-stub.c

@@ -9,6 +9,8 @@
 #include <linux/efi.h>
 #include <linux/pci.h>
 #include <linux/stddef.h>
+#include <linux/slr_table.h>
+#include <linux/slaunch.h>
 
 #include <asm/efi.h>
 #include <asm/e820/types.h>
@@ -795,6 +797,101 @@ static efi_status_t efi_decompress_kernel(unsigned long *kernel_entry,
 						  kernel_inittext_size);
 }
 
+#if (IS_ENABLED(CONFIG_SECURE_LAUNCH))
+
+static bool efi_secure_launch_update_boot_params(struct slr_table *slrt,
+						 struct boot_params *boot_params)
+{
+	struct slr_entry_intel_info *txt_info;
+	struct slr_entry_policy *policy;
+	bool updated = false;
+	int i;
+
+	txt_info = slr_next_entry_by_tag(slrt, NULL, SLR_ENTRY_INTEL_INFO);
+	if (!txt_info)
+		return false;
+
+	txt_info->boot_params_addr = (u64)boot_params;
+
+	policy = slr_next_entry_by_tag(slrt, NULL, SLR_ENTRY_ENTRY_POLICY);
+	if (!policy)
+		return false;
+
+	for (i = 0; i < policy->nr_entries; i++) {
+		if (policy->policy_entries[i].entity_type == SLR_ET_BOOT_PARAMS) {
+			policy->policy_entries[i].entity = (u64)boot_params;
+			updated = true;
+			break;
+		}
+	}
+
+	/*
+	 * If this is a PE entry into EFI stub the mocked up boot params will
+	 * be missing some of the setup header data needed for the second stage
+	 * of the Secure Launch boot.
+	 */
+	if (image) {
+		struct setup_header *hdr = (struct setup_header *)((u8 *)image->image_base +
+					    offsetof(struct boot_params, hdr));
+		u64 cmdline_ptr;
+
+		boot_params->hdr.setup_sects = hdr->setup_sects;
+		boot_params->hdr.syssize = hdr->syssize;
+		boot_params->hdr.version = hdr->version;
+		boot_params->hdr.loadflags = hdr->loadflags;
+		boot_params->hdr.kernel_alignment = hdr->kernel_alignment;
+		boot_params->hdr.min_alignment = hdr->min_alignment;
+		boot_params->hdr.xloadflags = hdr->xloadflags;
+		boot_params->hdr.init_size = hdr->init_size;
+		boot_params->hdr.kernel_info_offset = hdr->kernel_info_offset;
+		efi_set_u64_form(boot_params->hdr.cmd_line_ptr, boot_params->ext_cmd_line_ptr,
+				 &cmdline_ptr);
+		boot_params->hdr.cmdline_size = strlen((const char *)cmdline_ptr);
+	}
+
+	return updated;
+}
+
+static void efi_secure_launch(struct boot_params *boot_params)
+{
+	struct slr_entry_dl_info *dlinfo;
+	efi_guid_t guid = SLR_TABLE_GUID;
+	dl_handler_func handler_callback;
+	struct slr_table *slrt;
+
+	/*
+	 * The presence of this table indicated a Secure Launch
+	 * is being requested.
+	 */
+	slrt = (struct slr_table *)get_efi_config_table(guid);
+	if (!slrt || slrt->magic != SLR_TABLE_MAGIC)
+		return;
+
+	/*
+	 * Since the EFI stub library creates its own boot_params on entry, the
+	 * SLRT and TXT heap have to be updated with this version.
+	 */
+	if (!efi_secure_launch_update_boot_params(slrt, boot_params))
+		return;
+
+	/* Jump through DL stub to initiate Secure Launch */
+	dlinfo = slr_next_entry_by_tag(slrt, NULL, SLR_ENTRY_DL_INFO);
+
+	handler_callback = (dl_handler_func)dlinfo->dl_handler;
+
+	handler_callback(&dlinfo->bl_context);
+
+	unreachable();
+}
+
+#else
+
+static void efi_secure_launch(struct boot_params *boot_params)
+{
+}
+
+#endif /* IS_ENABLED(CONFIG_SECURE_LAUNCH) */
+
 static void __noreturn enter_kernel(unsigned long kernel_addr,
 				    struct boot_params *boot_params)
 {
@@ -929,6 +1026,9 @@ 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.