Re: [PATCH v5 2/2] x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernels

[Baoquan He]

On 04/24/19 at 05:29pm, Baoquan He wrote:
> From: Junichi Nomura <j-nomura@xxxxxxxxxxxxx>
> 
> 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 the EFI tables but that will
> crash because the table address is virtual when the kernel was booted by
> kexec (set_virtual_address_map() has run in the first kernel and cannot
> be run again in the second kernel).
> 
> In the case of kexec, the physical address of EFI tables is provided via
> efi_setup_data in boot_params, which is set up by kexec(1).
> 
> Factor out the table parsing code and use different pointers depending
> on whether the kernel is booted by kexec or not.
> 
>  [ bp: Massage. ]
> 
> Fixes: 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in boot_params")
> Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>
> Signed-off-by: Borislav Petkov <bp@xxxxxxx>
> Cc: Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxx>
> Cc: Dave Young <dyoung@xxxxxxxxxx>
> Link: https://lkml.kernel.org/r/20190408231011.GA5402@xxxxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>

Oops, forgot removing this line of Signed-off-by, it's auto generated by
git format-patch.

> ---
>  arch/x86/boot/compressed/acpi.c | 143 ++++++++++++++++++++++++--------
>  1 file changed, 107 insertions(+), 36 deletions(-)
> 
> diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
> index 0ef4ad55b29b..8cecce1ac0cd 100644
> --- a/arch/x86/boot/compressed/acpi.c
> +++ b/arch/x86/boot/compressed/acpi.c
> @@ -44,17 +44,109 @@ static acpi_physical_address get_acpi_rsdp(void)
>  	return addr;
>  }
>  
> -/* Search EFI system tables for RSDP. */
> -static acpi_physical_address efi_get_rsdp_addr(void)
> +/*
> + * Search EFI system tables for RSDP.  If both ACPI_20_TABLE_GUID and
> + * ACPI_TABLE_GUID are found, take the former, which has more features.
> + */
> +static acpi_physical_address
> +__efi_get_rsdp_addr(unsigned long config_tables, unsigned int nr_tables,
> +		    bool efi_64)
>  {
>  	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;
> +
> +		if (efi_64) {
> +			efi_config_table_64_t *tbl = (efi_config_table_64_t *) config_tables + i;
> +
> +			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 + i;
> +
> +			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;
> +}
> +
> +/* EFI/kexec support is 64-bit only. */
> +#ifdef CONFIG_X86_64
> +static struct efi_setup_data *get_kexec_setup_data_addr(void)
> +{
> +	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 (struct efi_setup_data *)(pa_data + sizeof(struct setup_data));
> +
> +		pa_data = data->next;
> +	}
> +	return NULL;
> +}
> +
> +static acpi_physical_address kexec_get_rsdp_addr(void)
> +{
> +	efi_system_table_64_t *systab;
> +	struct efi_setup_data *esd;
> +	struct efi_info *ei;
> +	char *sig;
> +
> +	esd = (struct efi_setup_data *)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 kexec 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 in kexec boot_params.");
> +
> +	return __efi_get_rsdp_addr((unsigned long)esd->tables, systab->nr_tables, true);
> +}
> +#else
> +static acpi_physical_address kexec_get_rsdp_addr(void) { return 0; }
> +#endif /* CONFIG_X86_64 */
> +
> +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;
>  	char *sig;
>  
>  	ei = &boot_params->efi_info;
> @@ -88,49 +180,20 @@ static acpi_physical_address efi_get_rsdp_addr(void)
>  
>  		config_tables	= stbl->tables;
>  		nr_tables	= stbl->nr_tables;
> -		size		= sizeof(efi_config_table_64_t);
>  	} else {
>  		efi_system_table_32_t *stbl = (efi_system_table_32_t *)systab;
>  
>  		config_tables	= stbl->tables;
>  		nr_tables	= stbl->nr_tables;
> -		size		= sizeof(efi_config_table_32_t);
>  	}
>  
>  	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, efi_64);
> +#else
> +	return 0;
>  #endif
> -	return rsdp_addr;
>  }
>  
>  static u8 compute_checksum(u8 *buffer, u32 length)
> @@ -220,6 +283,14 @@ acpi_physical_address get_rsdp_addr(void)
>  	if (!pa)
>  		pa = boot_params->acpi_rsdp_addr;
>  
> +	/*
> +	 * Try to get EFI data from setup_data. This can happen when we're a
> +	 * kexec'ed kernel and kexec(1) has passed all the required EFI info to
> +	 * us.
> +	 */
> +	if (!pa)
> +		pa = kexec_get_rsdp_addr();
> +
>  	if (!pa)
>  		pa = efi_get_rsdp_addr();
>  
> -- 
> 2.17.2
>