Re: [tip:x86/boot] x86/boot: Early parse RSDP and save it in boot_params

[Borislav Petkov]

On Mon, Feb 11, 2019 at 10:46:18AM +0000, Ard Biesheuvel wrote:
> As I pointed out in my previous reply, systab will be the wrong type
> on 32-bit firmware, it needs to be efi_system_table_32_t

This seems to work. Chao, please run it too.

Thx.

---
diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index c5a949335d8b..0d97aa8bd01f 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -50,7 +50,8 @@ static acpi_physical_address efi_get_rsdp_addr(void)
        acpi_physical_address rsdp_addr = 0;
 
 #ifdef CONFIG_EFI
-       efi_system_table_t *systab;
+       unsigned long systab, systab_tables, config_tables;
+       unsigned int nr_tables;
        struct efi_info *ei;
        bool efi_64;
        int size, i;
@@ -70,13 +71,13 @@ static acpi_physical_address efi_get_rsdp_addr(void)
 
        /* Get systab from boot params. */
 #ifdef CONFIG_X86_64
-       systab = (efi_system_table_t *)(ei->efi_systab | 
((__u64)ei->efi_systab_hi<<32));
+       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 = (efi_system_table_t *)ei->efi_systab;
+       systab = ei->efi_systab;
 #endif
        if (!systab)
                error("EFI system table not found.");
@@ -87,16 +88,30 @@ static acpi_physical_address efi_get_rsdp_addr(void)
        size = efi_64 ? sizeof(efi_config_table_64_t) :
                        sizeof(efi_config_table_32_t);
 
-       for (i = 0; i < systab->nr_tables; i++) {
+       if (efi_64) {
+               efi_system_table_64_t *st_tbl = (efi_system_table_64_t *)systab;
+
+               config_tables   = st_tbl->tables;
+               nr_tables       = st_tbl->nr_tables;
+       } else {
+               efi_system_table_32_t *st_tbl = (efi_system_table_32_t *)systab;
+
+               config_tables   = st_tbl->tables;
+               nr_tables       = st_tbl->nr_tables;
+       }
+
+       if (!config_tables)
+               error("EFI config tables not found.");
+
+       for (i = 0; i < nr_tables; i++) {
                acpi_physical_address table;
-               void *config_tables;
                efi_guid_t guid;
 
-               config_tables = (void *)(systab->tables + size * i);
+               config_tables += size * i;
+
                if (efi_64) {
-                       efi_config_table_64_t *tmp_table;
+                       efi_config_table_64_t *tmp_table = 
(efi_config_table_64_t *)config_tables;
 
-                       tmp_table = config_tables;
                        guid = tmp_table->guid;
                        table = tmp_table->table;
 
@@ -105,9 +120,8 @@ static acpi_physical_address efi_get_rsdp_addr(void)
                                return 0;
                        }
                } else {
-                       efi_config_table_32_t *tmp_table;
+                       efi_config_table_32_t *tmp_table = 
(efi_config_table_32_t *)config_tables;
 
-                       tmp_table = config_tables;
                        guid = tmp_table->guid;
                        table = tmp_table->table;
                }

-- 
Regards/Gruss,
    Boris.

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