x86/compressed/acpi: Move EFI config table lookup to helper

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.

  [ bp: Remove superfluous zeroing of a stack variable. ]

Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-27-brijesh.singh@amd.com

diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index 58a3d3f..9a824af 100644 (file)
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -118,10 +118,13 @@ 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_pa, config_tables;
+       unsigned long cfg_tbl_pa = 0;
+       unsigned int cfg_tbl_len;
+       unsigned long systab_pa;
        unsigned int nr_tables;
        enum efi_type et;
        bool efi_64;
+       int ret;
 
        et = efi_get_type(boot_params);
        if (et == EFI_TYPE_64)
@@ -135,23 +138,11 @@ static acpi_physical_address efi_get_rsdp_addr(void)
        if (!systab_pa)
                error("EFI support advertised, but unable to locate system table.");
 
-       /* Handle EFI bitness properly */
-       if (efi_64) {
-               efi_system_table_64_t *stbl = (efi_system_table_64_t *)systab_pa;
-
-               config_tables   = stbl->tables;
-               nr_tables       = stbl->nr_tables;
-       } else {
-               efi_system_table_32_t *stbl = (efi_system_table_32_t *)systab_pa;
-
-               config_tables   = stbl->tables;
-               nr_tables       = stbl->nr_tables;
-       }
-
-       if (!config_tables)
-               error("EFI config tables not found.");
+       ret = efi_get_conf_table(boot_params, &cfg_tbl_pa, &cfg_tbl_len);
+       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 72a81ba..350838e 100644 (file)
--- a/arch/x86/boot/compressed/efi.c
+++ b/arch/x86/boot/compressed/efi.c
@@ -77,3 +77,46 @@ unsigned long efi_get_system_table(struct boot_params *bp)
 
        return sys_tbl_pa;
 }
+
+/**
+ * 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;
+
+               *cfg_tbl_pa = 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;
+}

diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index b2acd3a..8815af0 100644 (file)
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -186,6 +186,8 @@ enum efi_type {
 /* helpers for early EFI config table access */
 enum efi_type efi_get_type(struct boot_params *bp);
 unsigned long efi_get_system_table(struct boot_params *bp);
+int efi_get_conf_table(struct boot_params *bp, unsigned long *cfg_tbl_pa,
+                      unsigned int *cfg_tbl_len);
 #else
 static inline enum efi_type efi_get_type(struct boot_params *bp)
 {
@@ -196,6 +198,13 @@ static inline unsigned long efi_get_system_table(struct boot_params *bp)
 {
        return 0;
 }
+
+static inline int efi_get_conf_table(struct boot_params *bp,
+                                    unsigned long *cfg_tbl_pa,
+                                    unsigned int *cfg_tbl_len)
+{
+       return -ENOENT;
+}
 #endif /* CONFIG_EFI */
 
 #endif /* BOOT_COMPRESSED_MISC_H */