Re: [PATCH v2] x86/boot: Use EFI setup data if provided

[bhe@xxxxxxxxxx]

On 03/28/19 at 07:43am, Junichi Nomura wrote:
> On 2019/03/28 15:43, bhe@xxxxxxxxxx wrote:
> > On 03/28/19 at 04:17am, Junichi Nomura wrote:
> >> I still don't get it... We still need systab for kexec case as well
> >> to get nr_tables. Don't we?
> > 
> > Yes, simpler.
> > 
> > As Dave replied in another mail, efi/kexec is only added for x86_64. See
> > how it does in setup_linux_system_parameters() of kexec_tools utility,
> > and we only have bzImage64 handling in kernel for kexec_file loading,
> > see prepare_add_efi_setup_data().
> > 
> > You may only need to get kexec ei_info to use directly.
> 
> OK, let me try. How does this look?

Yes, it looks great. Thanks.

Some tiny concenrns added in inline comments, please check.

> 
> Commit 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in
> boot_params") broke kexec boot on EFI systems.  efi_get_rsdp_addr()
> in the early parsing code tries to search RSDP from EFI table but
> that will crash because the table address is virtual when the kernel
> was booted by kexec.
> 
> Since kexec(1) provides physical address of the table via efi_setup_data,
> early boot code of kexec-ed kernel should look for setup_data in the same
> way as efi_systab_init() in arch/x86/platform/efi/efi.c does.
> 
> Fixes: 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in boot_params")
> Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>
> Cc: Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxx>
> Cc: Dave Young <dyoung@xxxxxxxxxx>
> Cc: Baoquan He <bhe@xxxxxxxxxx>
> 
> diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
> --- a/arch/x86/boot/compressed/acpi.c
> +++ b/arch/x86/boot/compressed/acpi.c
> @@ -44,17 +44,106 @@ static acpi_physical_address get_acpi_rsdp(void)
>  	return addr;
>  }
>  
> +static unsigned long efi_get_kexec_setup_data_addr(void)
> +{
> +#ifdef CONFIG_EFI
> +	struct setup_data *data;
> +	u64 pa_data;
> +
> +	pa_data = boot_params->hdr.setup_data;
> +	while (pa_data) {
> +		data = (struct setup_data *) pa_data;
> +		if (data->type == SETUP_EFI)
> +			return pa_data + sizeof(struct setup_data);
> +		pa_data = data->next;
> +	}
> +#endif
> +	return 0;
> +}
> +
>  /* Search EFI system tables for RSDP. */
> -static acpi_physical_address efi_get_rsdp_addr(void)
> +static acpi_physical_address __efi_get_rsdp_addr(unsigned long config_tables, unsigned int nr_tables, int size, bool efi_64)

Here parameter 'size' and 'efi_64' seems a little duplicated on
functionality. Only passing efi_64 can deduce the size? Personal
opinion.

>  {
>  	acpi_physical_address rsdp_addr = 0;
>  
>  #ifdef CONFIG_EFI
> -	unsigned long systab, systab_tables, config_tables;
> +	int i;
> +
> +	/* Get EFI tables from systab. */
> +	for (i = 0; i < nr_tables; i++) {
> +		acpi_physical_address table;
> +		efi_guid_t guid;
> +
> +		config_tables += size;
> +
> +		if (efi_64) {
> +			efi_config_table_64_t *tbl = (efi_config_table_64_t *)config_tables;
> +
> +			guid  = tbl->guid;
> +			table = tbl->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 *tbl = (efi_config_table_32_t *)config_tables;
> +
> +			guid  = tbl->guid;
> +			table = tbl->table;
> +		}
> +
> +		if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)))
> +			rsdp_addr = table;
> +		else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID)))
> +			return table;
> +	}
> +#endif
> +	return rsdp_addr;
> +}
> +

It might be worth adding code comments here to tell why we only care
about 64bit kexec booting?

> +static acpi_physical_address kexec_get_rsdp_addr(void)
> +{
> +#ifdef CONFIG_EFI
> +	struct efi_setup_data *esd;
> +	efi_system_table_64_t *systab;
> +	struct efi_info *ei;
> +	char *sig;
> +
> +	esd = (struct efi_setup_data *) efi_get_kexec_setup_data_addr();
> +	if (!esd)
> +		return 0;
> +	if (!esd->tables) {
> +		debug_putstr("Wrong kexec SETUP_EFI data.\n");
> +		return 0;
> +	}
> +
> +	ei = &boot_params->efi_info;
> +	sig = (char *)&ei->efi_loader_signature;
> +	if (strncmp(sig, EFI64_LOADER_SIGNATURE, 4)) {
> +		debug_putstr("Wrong EFI loader signature.\n");
> +		return 0;
> +	}
> +
> +	/* Get systab from boot params. */
> +	systab = (efi_system_table_64_t *) (ei->efi_systab | ((__u64)ei->efi_systab_hi << 32));
> +	if (!systab)
> +		error("EFI system table not found.");
> +
> +	return __efi_get_rsdp_addr((unsigned long) esd->tables, systab->nr_tables, sizeof(efi_config_table_64_t), true);
> +#else
> +	return 0;
> +#endif
> +}
> +
> +static acpi_physical_address efi_get_rsdp_addr(void)
> +{
> +#ifdef CONFIG_EFI
> +	unsigned long systab, config_tables;
>  	unsigned int nr_tables;
>  	struct efi_info *ei;
>  	bool efi_64;
> -	int size, i;
> +	int size;
>  	char *sig;
>  
>  	ei = &boot_params->efi_info;
> @@ -100,37 +189,10 @@ static acpi_physical_address efi_get_rsdp_addr(void)
>  	if (!config_tables)
>  		error("EFI config tables not found.");
>  
> -	/* Get EFI tables from systab. */
> -	for (i = 0; i < nr_tables; i++) {
> -		acpi_physical_address table;
> -		efi_guid_t guid;
> -
> -		config_tables += size;
> -
> -		if (efi_64) {
> -			efi_config_table_64_t *tbl = (efi_config_table_64_t *)config_tables;
> -
> -			guid  = tbl->guid;
> -			table = tbl->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 *tbl = (efi_config_table_32_t *)config_tables;
> -
> -			guid  = tbl->guid;
> -			table = tbl->table;
> -		}
> -
> -		if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)))
> -			rsdp_addr = table;
> -		else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID)))
> -			return table;
> -	}
> +	return __efi_get_rsdp_addr(config_tables, nr_tables, size, efi_64);
> +#else
> +	return 0;
>  #endif
> -	return rsdp_addr;
>  }
>  
>  static u8 compute_checksum(u8 *buffer, u32 length)
> @@ -221,6 +283,9 @@ acpi_physical_address get_rsdp_addr(void)
>  		pa = boot_params->acpi_rsdp_addr;
>  
>  	if (!pa)
> +		pa = kexec_get_rsdp_addr();
> +
> +	if (!pa)
>  		pa = efi_get_rsdp_addr();
>  
>  	if (!pa)