Re: [PATCH v15 3/6] x86/boot: Introduce efi_get_rsdp_addr() to find RSDP from EFI table

Borislav Petkov
2019-01-10T21:15:34Z

On Mon, Jan 07, 2019 at 11:22:40AM +0800, Chao Fan wrote:
> Memory information in SRAT is necessary to fix the conflict between
> KASLR and memory-hotremove. So RSDP and SRAT should be parsed.
>
> When booting form KEXEC/EFI/BIOS, the methods to compute RSDP
> are different. When booting from EFI, EFI table points to RSDP.
> So parse the EFI table and find the RSDP.
>
> Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
> ---
> arch/x86/boot/compressed/acpi.c | 83 +++++++++++++++++++++++++++++++++
> 1 file changed, 83 insertions(+)
>
> diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
> index 7ca5001d7639..f74c5d033d79 100644
> --- a/arch/x86/boot/compressed/acpi.c
> +++ b/arch/x86/boot/compressed/acpi.c
> @@ -5,6 +5,8 @@
> #include "../string.h"
>
> #include <linux/acpi.h>
> +#include <linux/efi.h>
> +#include <asm/efi.h>
>
> /*
> * Max length of 64-bit hex address string is 19, prefix "0x" + 16 hex
> @@ -28,3 +30,84 @@ static acpi_physical_address get_acpi_rsdp(void)
> #endif
> return 0;
> }
> +
> +/* Search EFI table for RSDP. */
> +static acpi_physical_address efi_get_rsdp_addr(void)
> +{
> + acpi_physical_address rsdp_addr = 0;

<---- newline here.

> +#ifdef CONFIG_EFI
> + efi_system_table_t *systab;
> + struct efi_info *ei;
> + bool efi_64;
> + char *sig;
> + int size;
> + int i;
> +
> + 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. Based on efi_init(). */
> +#ifdef CONFIG_X86_64
> + systab = (efi_system_table_t *)(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;
> +#endif
> +
> + if (!systab)
> + error("EFI system table is not found.");

s/is//

> +
> + /*
> + * Get EFI tables from systab. Based on efi_config_init() and
> + * efi_config_parse_tables().
> + */
> + size = efi_64 ? sizeof(efi_config_table_64_t) :
> + sizeof(efi_config_table_32_t);
> +
> + for (i = 0; i < systab->nr_tables; i++) {
> + void *config_tables;
> + unsigned long table;
> + efi_guid_t guid;
> +
> + config_tables = (void *)(systab->tables + size * i);
> + if (efi_64) {
> + efi_config_table_64_t *tmp_table;
> + u64 table64;
> +
> + tmp_table = config_tables;
> + guid = tmp_table->guid;
> + table64 = tmp_table->table;
> + table = table64;

That table64 looks superfluous.

--
Regards/Gruss,
Boris.

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