On Mon, Dec 17, 2018 at 06:30:32PM +0100, Ingo Molnar wrote:
>
>* Chao Fan <fanc.f...@cn.fujitsu.com> 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.f...@cn.fujitsu.com>
>> ---
>> arch/x86/boot/compressed/acpi.c | 79 +++++++++++++++++++++++++++++++++
>> 1 file changed, 79 insertions(+)
>>
>> diff --git a/arch/x86/boot/compressed/acpi.c
>> b/arch/x86/boot/compressed/acpi.c
>> index 44f19546c169..4151881d8713 100644
>> --- a/arch/x86/boot/compressed/acpi.c
>> +++ b/arch/x86/boot/compressed/acpi.c
>> @@ -28,3 +28,82 @@ 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;
>> +#ifdef CONFIG_EFI
>> + efi_system_table_t *systab;
>> + struct efi_info *e;
>
>'e' is pretty meaningless, the canonical name for efi_info local
>variables is typically 'ei' (although this is not consistent across the
>code).
OK, will change it.
>
>> + bool efi_64;
>
>Is this a flag that shows whether the EFI loader is 64-bit?
Yes, I use the signature to decide the size of EFI table.
It's used here:
+ size = efi_64 ? sizeof(efi_config_table_64_t) :
+ sizeof(efi_config_table_32_t);
>
>> + char *sig;
>> + int size;
>> + int i;
>> +
>> + e = &boot_params->efi_info;
>> + sig = (char *)&e->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 *)(e->efi_systab |
>> ((__u64)e->efi_systab_hi<<32));
>> +#else
>> + if (e->efi_systab_hi || e->efi_memmap_hi) {
>> + debug_putstr("Error getting RSDP address: EFI system table
>> located above 4GB.\n");
>> + return 0;
>> + }
>> + systab = (efi_system_table_t *)e->efi_systab;
>> +#endif
>> +
>> + if (!systab)
>> + return 0;
>
>Is it normal that EFI provides no 'systab'?
I think not normal, to make sure the code run normally.
We will use it below like: i < systab->nr_tables, if
systab is wrong, the code will fail to work.
>
>> + /*
>> + * 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;
>> +
>> + tmp_table = (efi_config_table_64_t *)config_tables;
>
>Since 'config_tables' is a void * there's no need to cast the type.
>
>> + guid = tmp_table->guid;
>> + table = tmp_table->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 *tmp_table;
>> +
>> + tmp_table = (efi_config_table_32_t *)config_tables;
>
>Ditto.
>
>> + guid = tmp_table->guid;
>> + table = tmp_table->table;
>> + }
>
>So it looks like
>
>> +
>> + if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)))
>> + rsdp_addr = (acpi_physical_address)table;
>> + else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID)))
>> + return (acpi_physical_address)table;
>
>'return' is not a function.
Got it, will clean the type cast.
Thanks,
Chao Fan
>
>Thanks,
>
> Ingo
>
>
