1 files changed, 234 insertions, 0 deletions
diff --git a/arch/x86/boot/compressed/efi.c b/arch/x86/boot/compressed/efi.c
new file mode 100644
index 0000000000..6edd034b0b
--- /dev/null
+++ b/arch/x86/boot/compressed/efi.c
@@ -0,0 +1,234 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Helpers for early access to EFI configuration table.
+ *
+ * Originally derived from arch/x86/boot/compressed/acpi.c
+ */
+
+#include "misc.h"
+
+/**
+ * efi_get_type - Given a pointer to boot_params, determine the type of EFI environment.
+ *
+ * @bp:         pointer to boot_params
+ *
+ * Return: EFI_TYPE_{32,64} for valid EFI environments, EFI_TYPE_NONE otherwise.
+ */
+enum efi_type efi_get_type(struct boot_params *bp)
+{
+	struct efi_info *ei;
+	enum efi_type et;
+	const char *sig;
+
+	ei = &bp->efi_info;
+	sig = (char *)&ei->efi_loader_signature;
+
+	if (!strncmp(sig, EFI64_LOADER_SIGNATURE, 4)) {
+		et = EFI_TYPE_64;
+	} else if (!strncmp(sig, EFI32_LOADER_SIGNATURE, 4)) {
+		et = EFI_TYPE_32;
+	} else {
+		debug_putstr("No EFI environment detected.\n");
+		et = EFI_TYPE_NONE;
+	}
+
+#ifndef CONFIG_X86_64
+	/*
+	 * Existing callers like acpi.c treat this case as an indicator to
+	 * fall-through to non-EFI, rather than an error, so maintain that
+	 * functionality here as well.
+	 */
+	if (ei->efi_systab_hi || ei->efi_memmap_hi) {
+		debug_putstr("EFI system table is located above 4GB and cannot be accessed.\n");
+		et = EFI_TYPE_NONE;
+	}
+#endif
+
+	return et;
+}
+
+/**
+ * efi_get_system_table - Given a pointer to boot_params, retrieve the physical address
+ *                        of the EFI system table.
+ *
+ * @bp:         pointer to boot_params
+ *
+ * Return: EFI system table address on success. On error, return 0.
+ */
+unsigned long efi_get_system_table(struct boot_params *bp)
+{
+	unsigned long sys_tbl_pa;
+	struct efi_info *ei;
+	enum efi_type et;
+
+	/* Get systab from boot params. */
+	ei = &bp->efi_info;
+#ifdef CONFIG_X86_64
+	sys_tbl_pa = ei->efi_systab | ((__u64)ei->efi_systab_hi << 32);
+#else
+	sys_tbl_pa = ei->efi_systab;
+#endif
+	if (!sys_tbl_pa) {
+		debug_putstr("EFI system table not found.");
+		return 0;
+	}
+
+	return sys_tbl_pa;
+}
+
+/*
+ * EFI config table address changes to virtual address after boot, which may
+ * not be accessible for the kexec'd kernel. To address this, kexec provides
+ * the initial physical address via a struct setup_data entry, which is
+ * checked for here, along with some sanity checks.
+ */
+static struct efi_setup_data *get_kexec_setup_data(struct boot_params *bp,
+						   enum efi_type et)
+{
+#ifdef CONFIG_X86_64
+	struct efi_setup_data *esd = NULL;
+	struct setup_data *data;
+	u64 pa_data;
+
+	pa_data = bp->hdr.setup_data;
+	while (pa_data) {
+		data = (struct setup_data *)pa_data;
+		if (data->type == SETUP_EFI) {
+			esd = (struct efi_setup_data *)(pa_data + sizeof(struct setup_data));
+			break;
+		}
+
+		pa_data = data->next;
+	}
+
+	/*
+	 * Original ACPI code falls back to attempting normal EFI boot in these
+	 * cases, so maintain existing behavior by indicating non-kexec
+	 * environment to the caller, but print them for debugging.
+	 */
+	if (esd && !esd->tables) {
+		debug_putstr("kexec EFI environment missing valid configuration table.\n");
+		return NULL;
+	}
+
+	return esd;
+#endif
+	return NULL;
+}
+
+/**
+ * efi_get_conf_table - Given a pointer to boot_params, locate and return the physical
+ *                      address of EFI configuration table.
+ *
+ * @bp:                 pointer to boot_params
+ * @cfg_tbl_pa:         location to store physical address of config table
+ * @cfg_tbl_len:        location to store number of config table entries
+ *
+ * Return: 0 on success. On error, return params are left unchanged.
+ */
+int efi_get_conf_table(struct boot_params *bp, unsigned long *cfg_tbl_pa,
+		       unsigned int *cfg_tbl_len)
+{
+	unsigned long sys_tbl_pa;
+	enum efi_type et;
+	int ret;
+
+	if (!cfg_tbl_pa || !cfg_tbl_len)
+		return -EINVAL;
+
+	sys_tbl_pa = efi_get_system_table(bp);
+	if (!sys_tbl_pa)
+		return -EINVAL;
+
+	/* Handle EFI bitness properly */
+	et = efi_get_type(bp);
+	if (et == EFI_TYPE_64) {
+		efi_system_table_64_t *stbl = (efi_system_table_64_t *)sys_tbl_pa;
+		struct efi_setup_data *esd;
+
+		/* kexec provides an alternative EFI conf table, check for it. */
+		esd = get_kexec_setup_data(bp, et);
+
+		*cfg_tbl_pa = esd ? esd->tables : stbl->tables;
+		*cfg_tbl_len = stbl->nr_tables;
+	} else if (et == EFI_TYPE_32) {
+		efi_system_table_32_t *stbl = (efi_system_table_32_t *)sys_tbl_pa;
+
+		*cfg_tbl_pa = stbl->tables;
+		*cfg_tbl_len = stbl->nr_tables;
+	} else {
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/* Get vendor table address/guid from EFI config table at the given index */
+static int get_vendor_table(void *cfg_tbl, unsigned int idx,
+			    unsigned long *vendor_tbl_pa,
+			    efi_guid_t *vendor_tbl_guid,
+			    enum efi_type et)
+{
+	if (et == EFI_TYPE_64) {
+		efi_config_table_64_t *tbl_entry = (efi_config_table_64_t *)cfg_tbl + idx;
+
+		if (!IS_ENABLED(CONFIG_X86_64) && tbl_entry->table >> 32) {
+			debug_putstr("Error: EFI config table entry located above 4GB.\n");
+			return -EINVAL;
+		}
+
+		*vendor_tbl_pa = tbl_entry->table;
+		*vendor_tbl_guid = tbl_entry->guid;
+
+	} else if (et == EFI_TYPE_32) {
+		efi_config_table_32_t *tbl_entry = (efi_config_table_32_t *)cfg_tbl + idx;
+
+		*vendor_tbl_pa = tbl_entry->table;
+		*vendor_tbl_guid = tbl_entry->guid;
+	} else {
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/**
+ * efi_find_vendor_table - Given EFI config table, search it for the physical
+ *                         address of the vendor table associated with GUID.
+ *
+ * @bp:                pointer to boot_params
+ * @cfg_tbl_pa:        pointer to EFI configuration table
+ * @cfg_tbl_len:       number of entries in EFI configuration table
+ * @guid:              GUID of vendor table
+ *
+ * Return: vendor table address on success. On error, return 0.
+ */
+unsigned long efi_find_vendor_table(struct boot_params *bp,
+				    unsigned long cfg_tbl_pa,
+				    unsigned int cfg_tbl_len,
+				    efi_guid_t guid)
+{
+	enum efi_type et;
+	unsigned int i;
+
+	et = efi_get_type(bp);
+	if (et == EFI_TYPE_NONE)
+		return 0;
+
+	for (i = 0; i < cfg_tbl_len; i++) {
+		unsigned long vendor_tbl_pa;
+		efi_guid_t vendor_tbl_guid;
+		int ret;
+
+		ret = get_vendor_table((void *)cfg_tbl_pa, i,
+				       &vendor_tbl_pa,
+				       &vendor_tbl_guid, et);
+		if (ret)
+			return 0;
+
+		if (!efi_guidcmp(guid, vendor_tbl_guid))
+			return vendor_tbl_pa;
+	}
+
+	return 0;
+}