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From:   Brijesh Singh <brijesh.singh@amd.com>
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        npmccallum@redhat.com, brijesh.ksingh@gmail.com,
        Brijesh Singh <brijesh.singh@amd.com>
Subject: [PATCH Part1 RFC v4 24/36] x86/compressed/acpi: move EFI config table access to common code
Date:   Wed,  7 Jul 2021 13:14:54 -0500
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From: Michael Roth <michael.roth@amd.com>

Future patches for SEV-SNP-validated CPUID will also require early
parsing of the EFI configuration. Move the related code into a set of
helpers that can be re-used for that purpose.

Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 arch/x86/boot/compressed/Makefile           |   1 +
 arch/x86/boot/compressed/acpi.c             | 124 +++++---------
 arch/x86/boot/compressed/efi-config-table.c | 180 ++++++++++++++++++++
 arch/x86/boot/compressed/misc.h             |  50 ++++++
 4 files changed, 272 insertions(+), 83 deletions(-)
 create mode 100644 arch/x86/boot/compressed/efi-config-table.c

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 431bf7f846c3..b41aecfda49c 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -100,6 +100,7 @@ endif
 vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o
 
 vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_thunk_$(BITS).o
+vmlinux-objs-$(CONFIG_EFI) += $(obj)/efi-config-table.o
 efi-obj-$(CONFIG_EFI_STUB) = $(objtree)/drivers/firmware/efi/libstub/lib.a
 
 $(obj)/vmlinux: $(vmlinux-objs-y) $(efi-obj-y) FORCE
diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index 8bcbcee54aa1..e087dcaf43b3 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -24,42 +24,36 @@ struct mem_vector immovable_mem[MAX_NUMNODES*2];
  * Search EFI system tables for RSDP.  If both ACPI_20_TABLE_GUID and
  * ACPI_TABLE_GUID are found, take the former, which has more features.
  */
+#ifdef CONFIG_EFI
+static bool
+rsdp_find_fn(efi_guid_t guid, unsigned long vendor_table, bool efi_64,
+	     void *opaque)
+{
+	acpi_physical_address *rsdp_addr = opaque;
+
+	if (!(efi_guidcmp(guid, ACPI_TABLE_GUID))) {
+		*rsdp_addr = vendor_table;
+	} else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID))) {
+		*rsdp_addr = vendor_table;
+		return false;
+	}
+
+	return true;
+}
+#endif
+
 static acpi_physical_address
-__efi_get_rsdp_addr(unsigned long config_tables, unsigned int nr_tables,
+__efi_get_rsdp_addr(unsigned long config_table_pa, unsigned int config_table_len,
 		    bool efi_64)
 {
 	acpi_physical_address rsdp_addr = 0;
-
 #ifdef CONFIG_EFI
-	int i;
-
-	/* Get EFI tables from systab. */
-	for (i = 0; i < nr_tables; i++) {
-		acpi_physical_address table;
-		efi_guid_t guid;
-
-		if (efi_64) {
-			efi_config_table_64_t *tbl = (efi_config_table_64_t *)config_tables + i;
-
-			guid  = tbl->guid;
-			table = tbl->table;
-
-			if (!IS_ENABLED(CONFIG_X86_64) && table >> 32) {
-				debug_putstr("Error getting RSDP address: EFI config table located above 4GB.\n");
-				return 0;
-			}
-		} else {
-			efi_config_table_32_t *tbl = (efi_config_table_32_t *)config_tables + i;
-
-			guid  = tbl->guid;
-			table = tbl->table;
-		}
+	int ret;
 
-		if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)))
-			rsdp_addr = table;
-		else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID)))
-			return table;
-	}
+	ret = efi_foreach_conf_entry((void *)config_table_pa, config_table_len,
+				     efi_64, rsdp_find_fn, &rsdp_addr);
+	if (ret)
+		debug_putstr("Error getting RSDP address.\n");
 #endif
 	return rsdp_addr;
 }
@@ -87,7 +81,9 @@ static acpi_physical_address kexec_get_rsdp_addr(void)
 	efi_system_table_64_t *systab;
 	struct efi_setup_data *esd;
 	struct efi_info *ei;
+	bool efi_64;
 	char *sig;
+	int ret;
 
 	esd = (struct efi_setup_data *)get_kexec_setup_data_addr();
 	if (!esd)
@@ -98,18 +94,16 @@ static acpi_physical_address kexec_get_rsdp_addr(void)
 		return 0;
 	}
 
-	ei = &boot_params->efi_info;
-	sig = (char *)&ei->efi_loader_signature;
-	if (strncmp(sig, EFI64_LOADER_SIGNATURE, 4)) {
+	/* Get systab from boot params. */
+	ret = efi_bp_get_system_table(boot_params, (unsigned long *)&systab, &efi_64);
+	if (ret)
+		error("EFI system table not found in kexec boot_params.");
+
+	if (!efi_64) {
 		debug_putstr("Wrong kexec EFI loader signature.\n");
 		return 0;
 	}
 
-	/* Get systab from boot params. */
-	systab = (efi_system_table_64_t *) (ei->efi_systab | ((__u64)ei->efi_systab_hi << 32));
-	if (!systab)
-		error("EFI system table not found in kexec boot_params.");
-
 	return __efi_get_rsdp_addr((unsigned long)esd->tables, systab->nr_tables, true);
 }
 #else
@@ -119,54 +113,18 @@ static acpi_physical_address kexec_get_rsdp_addr(void) { return 0; }
 static acpi_physical_address efi_get_rsdp_addr(void)
 {
 #ifdef CONFIG_EFI
-	unsigned long systab, config_tables;
-	unsigned int nr_tables;
-	struct efi_info *ei;
+	unsigned long config_table_pa = 0;
+	unsigned int config_table_len;
 	bool efi_64;
-	char *sig;
-
-	ei = &boot_params->efi_info;
-	sig = (char *)&ei->efi_loader_signature;
-
-	if (!strncmp(sig, EFI64_LOADER_SIGNATURE, 4)) {
-		efi_64 = true;
-	} else if (!strncmp(sig, EFI32_LOADER_SIGNATURE, 4)) {
-		efi_64 = false;
-	} else {
-		debug_putstr("Wrong EFI loader signature.\n");
-		return 0;
-	}
-
-	/* Get systab from boot params. */
-#ifdef CONFIG_X86_64
-	systab = ei->efi_systab | ((__u64)ei->efi_systab_hi << 32);
-#else
-	if (ei->efi_systab_hi || ei->efi_memmap_hi) {
-		debug_putstr("Error getting RSDP address: EFI system table located above 4GB.\n");
-		return 0;
-	}
-	systab = ei->efi_systab;
-#endif
-	if (!systab)
-		error("EFI system table not found.");
-
-	/* Handle EFI bitness properly */
-	if (efi_64) {
-		efi_system_table_64_t *stbl = (efi_system_table_64_t *)systab;
-
-		config_tables	= stbl->tables;
-		nr_tables	= stbl->nr_tables;
-	} else {
-		efi_system_table_32_t *stbl = (efi_system_table_32_t *)systab;
-
-		config_tables	= stbl->tables;
-		nr_tables	= stbl->nr_tables;
-	}
+	int ret;
 
-	if (!config_tables)
-		error("EFI config tables not found.");
+	ret = efi_bp_get_conf_table(boot_params, &config_table_pa,
+				    &config_table_len, &efi_64);
+	if (ret || !config_table_pa)
+		error("EFI config table not found.");
 
-	return __efi_get_rsdp_addr(config_tables, nr_tables, efi_64);
+	return __efi_get_rsdp_addr(config_table_pa, config_table_len,
+				   efi_64);
 #else
 	return 0;
 #endif
diff --git a/arch/x86/boot/compressed/efi-config-table.c b/arch/x86/boot/compressed/efi-config-table.c
new file mode 100644
index 000000000000..d1a34aa7cefd
--- /dev/null
+++ b/arch/x86/boot/compressed/efi-config-table.c
@@ -0,0 +1,180 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Helpers for early access to EFI configuration table
+ *
+ * Copyright (C) 2021 Advanced Micro Devices, Inc.
+ *
+ * Author: Michael Roth <michael.roth@amd.com>
+ */
+
+#include "misc.h"
+#include <linux/efi.h>
+#include <asm/efi.h>
+
+/* Get vendor table address/guid from EFI config table at the given index */
+static int get_vendor_table(void *conf_table, unsigned int idx,
+			    unsigned long *vendor_table_pa,
+			    efi_guid_t *vendor_table_guid,
+			    bool efi_64)
+{
+	if (efi_64) {
+		efi_config_table_64_t *table_entry =
+			(efi_config_table_64_t *)conf_table + idx;
+
+		if (!IS_ENABLED(CONFIG_X86_64) &&
+		    table_entry->table >> 32) {
+			debug_putstr("Error: EFI config table entry located above 4GB.\n");
+			return -EINVAL;
+		}
+
+		*vendor_table_pa = table_entry->table;
+		*vendor_table_guid = table_entry->guid;
+
+	} else {
+		efi_config_table_32_t *table_entry =
+			(efi_config_table_32_t *)conf_table + idx;
+
+		*vendor_table_pa = table_entry->table;
+		*vendor_table_guid = table_entry->guid;
+	}
+
+	return 0;
+}
+
+/*
+ * Iterate through the entries in the EFI configuration table and pass the
+ * associated GUID/physical address of each entry on the provided callback
+ * function.
+ *
+ * @conf_table:         pointer to EFI configuration table
+ * @conf_table_len:     number of entries in EFI configuration table
+ * @efi_64:             true if using 64-bit EFI
+ * @fn:                 callback function that returns true if iteration
+ *                      should continue
+ * @opaque:             optional caller-provided data structure to pass to
+ *                      callback function on each iteration
+ *
+ * Returns 0 on success.
+ */
+int
+efi_foreach_conf_entry(void *conf_table, unsigned int conf_table_len,
+		       bool efi_64, bool (*fn)(efi_guid_t vendor_table_guid,
+					       unsigned long vendor_table_pa,
+					       bool efi_64,
+					       void *opaque),
+		       void *opaque)
+{
+	unsigned int i;
+
+	for (i = 0; i < conf_table_len; i++) {
+		unsigned long vendor_table_pa;
+		efi_guid_t vendor_table_guid;
+
+		if (get_vendor_table(conf_table, i, &vendor_table_pa,
+				     &vendor_table_guid, efi_64))
+			return -EINVAL;
+
+		if (!fn(vendor_table_guid, vendor_table_pa, efi_64, opaque))
+			break;
+	}
+
+	return 0;
+}
+
+/*
+ * Given boot_params, retrieve the physical address of EFI system table.
+ *
+ * @boot_params:        pointer to boot_params
+ * @sys_table_pa:       location to store physical address of system table
+ * @is_efi_64:          location to store whether using 64-bit EFI or not
+ *
+ * Returns 0 on success. On error, return params are left unchanged.
+ */
+int
+efi_bp_get_system_table(struct boot_params *boot_params,
+			unsigned long *sys_table_pa, bool *is_efi_64)
+{
+	unsigned long sys_table;
+	struct efi_info *ei;
+	bool efi_64;
+	char *sig;
+
+	if (!sys_table_pa || !is_efi_64)
+		return -EINVAL;
+
+	ei = &boot_params->efi_info;
+	sig = (char *)&ei->efi_loader_signature;
+
+	if (!strncmp(sig, EFI64_LOADER_SIGNATURE, 4)) {
+		efi_64 = true;
+	} else if (!strncmp(sig, EFI32_LOADER_SIGNATURE, 4)) {
+		efi_64 = false;
+	} else {
+		debug_putstr("Wrong EFI loader signature.\n");
+		return -ENOENT;
+	}
+
+	/* Get systab from boot params. */
+#ifdef CONFIG_X86_64
+	sys_table = ei->efi_systab | ((__u64)ei->efi_systab_hi << 32);
+#else
+	if (ei->efi_systab_hi || ei->efi_memmap_hi) {
+		debug_putstr("Error: EFI system table located above 4GB.\n");
+		return -EINVAL;
+	}
+	sys_table = ei->efi_systab;
+#endif
+	if (!sys_table) {
+		debug_putstr("EFI system table not found.");
+		return -ENOENT;
+	}
+
+	*sys_table_pa = sys_table;
+	*is_efi_64 = efi_64;
+	return 0;
+}
+
+/*
+ * Given boot_params, locate EFI system table from it and return the physical
+ * address EFI configuration table.
+ *
+ * @boot_params:        pointer to boot_params
+ * @conf_table_pa:      location to store physical address of config table
+ * @conf_table_len:     location to store number of config table entries
+ * @is_efi_64:          location to store whether using 64-bit EFI or not
+ *
+ * Returns 0 on success. On error, return params are left unchanged.
+ */
+int
+efi_bp_get_conf_table(struct boot_params *boot_params,
+		      unsigned long *conf_table_pa,
+		      unsigned int *conf_table_len,
+		      bool *is_efi_64)
+{
+	unsigned long sys_table_pa = 0;
+	int ret;
+
+	if (!conf_table_pa || !conf_table_len || !is_efi_64)
+		return -EINVAL;
+
+	ret = efi_bp_get_system_table(boot_params, &sys_table_pa, is_efi_64);
+	if (ret)
+		return ret;
+
+	/* Handle EFI bitness properly */
+	if (*is_efi_64) {
+		efi_system_table_64_t *stbl =
+			(efi_system_table_64_t *)sys_table_pa;
+
+		*conf_table_pa	= stbl->tables;
+		*conf_table_len	= stbl->nr_tables;
+	} else {
+		efi_system_table_32_t *stbl =
+			(efi_system_table_32_t *)sys_table_pa;
+
+		*conf_table_pa	= stbl->tables;
+		*conf_table_len	= stbl->nr_tables;
+	}
+
+	return 0;
+}
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 822e0c254b9a..522baf8ff04a 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -21,6 +21,7 @@
 #include <linux/screen_info.h>
 #include <linux/elf.h>
 #include <linux/io.h>
+#include <linux/efi.h>
 #include <asm/page.h>
 #include <asm/boot.h>
 #include <asm/bootparam.h>
@@ -174,4 +175,53 @@ void boot_stage2_vc(void);
 
 unsigned long sev_verify_cbit(unsigned long cr3);
 
+#ifdef CONFIG_EFI
+/* helpers for early EFI config table access */
+int efi_foreach_conf_entry(void *conf_table, unsigned int conf_table_len,
+			   bool efi_64,
+			   bool (*fn)(efi_guid_t guid,
+				      unsigned long vendor_table_pa,
+				      bool efi_64,
+				      void *opaque),
+			   void *opaque);
+
+int efi_bp_get_system_table(struct boot_params *boot_params,
+			    unsigned long *sys_table_pa,
+			    bool *is_efi_64);
+
+int efi_bp_get_conf_table(struct boot_params *boot_params,
+			  unsigned long *conf_table_pa,
+			  unsigned int *conf_table_len,
+			  bool *is_efi_64);
+#else
+static inline int
+efi_foreach_conf_entry(void *conf_table, unsigned int conf_table_len,
+		       bool efi_64,
+		       bool (*fn)(efi_guid_t guid,
+				  unsigned long vendor_table_pa,
+				  bool efi_64,
+				  void *opaque),
+		       void *opaque);
+{
+	return -ENOENT;
+}
+
+static inline int
+efi_bp_get_system_table(struct boot_params *boot_params,
+			unsigned long *sys_table_pa,
+			bool *is_efi_64)
+{
+	return -ENOENT;
+}
+
+static inline int
+efi_bp_get_conf_table(struct boot_params *boot_params,
+		      unsigned long *conf_table_pa,
+		      unsigned int *conf_table_len,
+		      bool *is_efi_64)
+{
+	return -ENOENT;
+}
+#endif /* CONFIG_EFI */
+
 #endif /* BOOT_COMPRESSED_MISC_H */
-- 
2.17.1