[PATCH v6 29/42] x86/compressed/acpi: move EFI config table lookup to helper

[Brijesh Singh <brijesh.singh@amd.com>]

From: Michael Roth <michael.roth@amd.com>

Future patches for SEV-SNP-validated CPUID will also require early
parsing of the EFI configuration. Incrementally 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/acpi.c | 52 +++++----------------------------
 arch/x86/boot/compressed/efi.c  | 42 ++++++++++++++++++++++++++
 arch/x86/boot/compressed/misc.h |  9 ++++++
 3 files changed, 58 insertions(+), 45 deletions(-)

diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index 255f6959c090..d43ff3ff573b 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -117,54 +117,16 @@ 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 cfg_tbl_pa = 0;
+	unsigned int cfg_tbl_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_get_conf_table(boot_params, &cfg_tbl_pa, &cfg_tbl_len, &efi_64);
+	if (ret || !cfg_tbl_pa)
+		error("EFI config table not found.");
 
-	return __efi_get_rsdp_addr(config_tables, nr_tables, efi_64);
+	return __efi_get_rsdp_addr(cfg_tbl_pa, cfg_tbl_len, efi_64);
 #else
 	return 0;
 #endif
diff --git a/arch/x86/boot/compressed/efi.c b/arch/x86/boot/compressed/efi.c
index 306b287b7368..e5f39b3f5665 100644
--- a/arch/x86/boot/compressed/efi.c
+++ b/arch/x86/boot/compressed/efi.c
@@ -62,3 +62,45 @@ int efi_get_system_table(struct boot_params *boot_params, unsigned long *sys_tbl
 	*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
+ * @cfg_tbl_pa:         location to store physical address of config table
+ * @cfg_tbl_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_get_conf_table(struct boot_params *boot_params, unsigned long *cfg_tbl_pa,
+		       unsigned int *cfg_tbl_len, bool *is_efi_64)
+{
+	unsigned long sys_tbl_pa = 0;
+	int ret;
+
+	if (!cfg_tbl_pa || !cfg_tbl_len || !is_efi_64)
+		return -EINVAL;
+
+	ret = efi_get_system_table(boot_params, &sys_tbl_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_tbl_pa;
+
+		*cfg_tbl_pa	= stbl->tables;
+		*cfg_tbl_len	= stbl->nr_tables;
+	} else {
+		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;
+	}
+
+	return 0;
+}
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index f86ff866fd7a..b72fd860362a 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -179,6 +179,8 @@ unsigned long sev_verify_cbit(unsigned long cr3);
 /* helpers for early EFI config table access */
 int efi_get_system_table(struct boot_params *boot_params,
 			 unsigned long *sys_tbl_pa, bool *is_efi_64);
+int efi_get_conf_table(struct boot_params *boot_params, unsigned long *cfg_tbl_pa,
+			unsigned int *cfg_tbl_len, bool *is_efi_64);
 #else
 static inline int
 efi_get_system_table(struct boot_params *boot_params,
@@ -186,6 +188,13 @@ efi_get_system_table(struct boot_params *boot_params,
 {
 	return -ENOENT;
 }
+
+static inline int
+efi_get_conf_table(struct boot_params *boot_params, unsigned long *cfg_tbl_pa,
+		   unsigned int *cfg_tbl_len, bool *is_efi_64)
+{
+	return -ENOENT;
+}
 #endif /* CONFIG_EFI */
 
 #endif /* BOOT_COMPRESSED_MISC_H */
-- 
2.25.1