linux-kernel - Re: [PATCH v13 3/6] x86/boot: Introduce efi_get_rsdp

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Date:   Fri, 14 Dec 2018 09:28:51 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <hpa@...or.com>,
        <keescook@...omium.org>, <bhe@...hat.com>, <msys.mizuma@...il.com>,
        <indou.takao@...fujitsu.com>, <caoj.fnst@...fujitsu.com>
Subject: Re: [PATCH v13 3/6] x86/boot: Introduce efi_get_rsdp_addr() to find
 RSDP from EFI table

On Thu, Dec 13, 2018 at 09:23:04PM +0100, Borislav Petkov wrote:
>On Wed, Dec 12, 2018 at 11:10:50AM +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@...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 cad15686f82c..c96008712ec9 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)
>>  	return 0;
>>  #endif
>>  }
>> +
>> +/* Search EFI table for RSDP. */
>> +static acpi_physical_address efi_get_rsdp_addr(void)
>> +{
>> +#ifdef CONFIG_EFI
>> +	acpi_physical_address rsdp_addr = 0;
>> +	efi_system_table_t *systab;
>> +	struct efi_info *e;
>> +	bool efi_64;
>> +	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;
>> +	}
>
>Use curly braces for all three branches above.
>

OK, I will add in the first and second.

>> +
>> +	/* 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;
>> +
>> +	/*
>> +	 * 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;
>> +			guid = tmp_table->guid;
>> +			table = tmp_table->table;
>> +
>> +			if (!IS_ENABLED(CONFIG_X86_64) && table >> 32) {
>> +				debug_putstr("Error getting RSDP address: EFI system table located above 4GB.\n");
>
>Do s/system/config/ here so that this error message is different from
>the one above.

Yes, will change it.

>
>> +				return 0;
>> +			}
>> +		} else {
>> +			efi_config_table_32_t *tmp_table;
>> +
>> +			tmp_table = (efi_config_table_32_t *)config_tables;
>> +			guid = tmp_table->guid;
>> +			table = tmp_table->table;
>> +		}
>> +
>> +		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 rsdp_addr;
>> +#endif
>
>	}
>#endif
>	return rsdp_addr;
>}
>
>IOW, you have:
>
>static acpi_physical_address efi_get_rsdp_addr(void)
>{
>        acpi_physical_address rsdp_addr = 0;
>#ifdef CONFIG_EFI
>	...
>#endif
>	return rsdp_addr;
>}

Make sense. Thanks.

Thanks,
Chao Fan

>
>-- 
>Regards/Gruss,
>    Boris.
>
>Good mailing practices for 400: avoid top-posting and trim the reply.
>
>