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From:   Arvind Sankar <nivedita@alum.mit.edu>
Date:   Sun, 16 Feb 2020 14:12:19 -0500
To:     Ard Biesheuvel <ardb@kernel.org>
Cc:     linux-efi@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, nivedita@alum.mit.edu, x86@kernel.org
Subject: Re: [PATCH 12/18] efi: clean up config_parse_tables()
Message-ID: <20200216191219.GA589207@rani.riverdale.lan>
References: <20200216182334.8121-1-ardb@kernel.org>
 <20200216182334.8121-13-ardb@kernel.org>
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On Sun, Feb 16, 2020 at 07:23:28PM +0100, Ard Biesheuvel wrote:
> config_parse_tables() is a jumble of pointer arithmetic, due to the
> fact that on x86, we may be dealing with firmware whose native word
> size differs from the kernel's.
> 
> This is not a concern on other architectures, and doesn't quite
> justify the state of the code, so let's clean it up by adding a
> non-x86 code path, constifying statically allocated tables and
> replacing preprocessor conditionals with IS_ENABLED() checks.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>  arch/ia64/kernel/efi.c          |  3 +-
>  arch/x86/platform/efi/efi.c     |  6 +--
>  drivers/firmware/efi/arm-init.c |  5 +--
>  drivers/firmware/efi/efi.c      | 47 ++++++++++----------
>  include/linux/efi.h             |  5 ++-
>  5 files changed, 32 insertions(+), 34 deletions(-)
> 
> diff --git a/arch/ia64/kernel/efi.c b/arch/ia64/kernel/efi.c
> index 3b5cf551489c..f69f3fe0532e 100644
> --- a/arch/ia64/kernel/efi.c
> +++ b/arch/ia64/kernel/efi.c
> @@ -56,7 +56,7 @@ unsigned long __initdata esi_phys = EFI_INVALID_TABLE_ADDR;
>  unsigned long hcdp_phys = EFI_INVALID_TABLE_ADDR;
>  unsigned long sal_systab_phys = EFI_INVALID_TABLE_ADDR;
>  
> -static __initdata efi_config_table_type_t arch_tables[] = {
> +static const efi_config_table_type_t arch_tables[] __initconst = {
>  	{ESI_TABLE_GUID, "ESI", &esi_phys},
>  	{HCDP_TABLE_GUID, "HCDP", &hcdp_phys},
>  	{MPS_TABLE_GUID, "MPS", &mps_phys},
> @@ -533,7 +533,6 @@ efi_init (void)
>  
>  	if (efi_config_parse_tables(__va(efi_systab->tables),
>  				    efi_systab->nr_tables,
> -				    sizeof(efi_config_table_t),
>  				    arch_tables) != 0)
>  		return;
>  
> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
> index 26d905e6b579..f7025b9075b4 100644
> --- a/arch/x86/platform/efi/efi.c
> +++ b/arch/x86/platform/efi/efi.c
> @@ -60,7 +60,7 @@ static u64 efi_systab_phys __initdata;
>  static unsigned long prop_phys = EFI_INVALID_TABLE_ADDR;
>  static unsigned long uga_phys = EFI_INVALID_TABLE_ADDR;
>  
> -static efi_config_table_type_t arch_tables[] __initdata = {
> +static const efi_config_table_type_t arch_tables[] __initconst = {
>  	{EFI_PROPERTIES_TABLE_GUID, "PROP", &prop_phys},
>  	{UGA_IO_PROTOCOL_GUID, "UGA", &uga_phys},
>  #ifdef CONFIG_X86_UV
> @@ -434,7 +434,7 @@ static int __init efi_systab_init(u64 phys)
>  	return 0;
>  }
>  
> -static int __init efi_config_init(efi_config_table_type_t *arch_tables)
> +static int __init efi_config_init(const efi_config_table_type_t *arch_tables)
>  {
>  	void *config_tables;
>  	int sz, ret;
> @@ -457,7 +457,7 @@ static int __init efi_config_init(efi_config_table_type_t *arch_tables)
>  		return -ENOMEM;
>  	}
>  
> -	ret = efi_config_parse_tables(config_tables, efi.systab->nr_tables, sz,
> +	ret = efi_config_parse_tables(config_tables, efi.systab->nr_tables,
>  				      arch_tables);
>  
>  	early_memunmap(config_tables, efi.systab->nr_tables * sz);
> diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c
> index a656bfcd7e27..d1f44c847841 100644
> --- a/drivers/firmware/efi/arm-init.c
> +++ b/drivers/firmware/efi/arm-init.c
> @@ -55,7 +55,7 @@ static phys_addr_t efi_to_phys(unsigned long addr)
>  
>  static __initdata unsigned long screen_info_table = EFI_INVALID_TABLE_ADDR;
>  
> -static __initdata efi_config_table_type_t arch_tables[] = {
> +static const efi_config_table_type_t arch_tables[] __initconst = {
>  	{LINUX_EFI_ARM_SCREEN_INFO_TABLE_GUID, NULL, &screen_info_table},
>  	{NULL_GUID, NULL, NULL}
>  };
> @@ -85,7 +85,7 @@ static void __init init_screen_info(void)
>  
>  static int __init uefi_init(void)
>  {
> -	void *config_tables;
> +	efi_config_table_t *config_tables;
>  	size_t table_size;
>  	int retval;
>  
> @@ -118,7 +118,6 @@ static int __init uefi_init(void)
>  		goto out;
>  	}
>  	retval = efi_config_parse_tables(config_tables, efi.systab->nr_tables,
> -					 sizeof(efi_config_table_t),
>  					 arch_tables);
>  
>  	if (!retval)
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index 2bfd6c0806ce..db1fe765380f 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -460,7 +460,7 @@ void __init efi_mem_reserve(phys_addr_t addr, u64 size)
>  	efi_arch_mem_reserve(addr, size);
>  }
>  
> -static __initdata efi_config_table_type_t common_tables[] = {
> +static const efi_config_table_type_t common_tables[] __initconst = {
>  	{ACPI_20_TABLE_GUID, "ACPI 2.0", &efi.acpi20},
>  	{ACPI_TABLE_GUID, "ACPI", &efi.acpi},
>  	{SMBIOS_TABLE_GUID, "SMBIOS", &efi.smbios},
> @@ -477,9 +477,9 @@ static __initdata efi_config_table_type_t common_tables[] = {
>  	{NULL_GUID, NULL, NULL},
>  };
>  
> -static __init int match_config_table(efi_guid_t *guid,
> +static __init int match_config_table(const efi_guid_t *guid,
>  				     unsigned long table,
> -				     efi_config_table_type_t *table_types)
> +				     const efi_config_table_type_t *table_types)
>  {
>  	int i;
>  
> @@ -498,39 +498,38 @@ static __init int match_config_table(efi_guid_t *guid,
>  	return 0;
>  }
>  
> -int __init efi_config_parse_tables(void *config_tables, int count, int sz,
> -				   efi_config_table_type_t *arch_tables)
> +int __init efi_config_parse_tables(const efi_config_table_t *config_tables,
> +				   int count,
> +				   const efi_config_table_type_t *arch_tables)
>  {
> -	void *tablep;
> +	const efi_config_table_64_t *tbl64 = (void *)config_tables;
> +	const efi_config_table_32_t *tbl32 = (void *)config_tables;
> +	const efi_guid_t *guid;
> +	unsigned long table;
>  	int i;
>  
> -	tablep = config_tables;
>  	pr_info("");
>  	for (i = 0; i < count; i++) {
> -		efi_guid_t guid;
> -		unsigned long table;
> -
> -		if (efi_enabled(EFI_64BIT)) {
> -			u64 table64;
> -			guid = ((efi_config_table_64_t *)tablep)->guid;
> -			table64 = ((efi_config_table_64_t *)tablep)->table;
> -			table = table64;
> -#ifndef CONFIG_64BIT
> -			if (table64 >> 32) {
> +		if (!IS_ENABLED(CONFIG_X86)) {
> +			guid = &config_tables[i].guid;
> +			table = (unsigned long)config_tables[i].table;
> +		} else if (efi_enabled(EFI_64BIT)) {
> +			guid = &tbl64[i].guid;
> +			table = tbl64[i].table;
> +
> +			if (IS_ENABLED(CONFIG_X64_32) &&
					      ^^^ typo, should be X86

> +			    tbl64[i].table > U32_MAX) {
>  				pr_cont("\n");
>  				pr_err("Table located above 4GB, disabling EFI.\n");
>  				return -EINVAL;
>  			}
> -#endif
>  		} else {
> -			guid = ((efi_config_table_32_t *)tablep)->guid;
> -			table = ((efi_config_table_32_t *)tablep)->table;
> +			guid = &tbl32[i].guid;
> +			table = tbl32[i].table;
>  		}
>  
> -		if (!match_config_table(&guid, table, common_tables))
> -			match_config_table(&guid, table, arch_tables);
> -
> -		tablep += sz;
> +		if (!match_config_table(guid, table, common_tables))
> +			match_config_table(guid, table, arch_tables);
>  	}
>  	pr_cont("\n");
>  	set_bit(EFI_CONFIG_TABLES, &efi.flags);
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index d61c25fd5824..99a7fcbe5e9b 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -613,8 +613,9 @@ extern void __init efi_esrt_init(void);
>  #else
>  static inline void efi_esrt_init(void) { }
>  #endif
> -extern int efi_config_parse_tables(void *config_tables, int count, int sz,
> -				   efi_config_table_type_t *arch_tables);
> +extern int efi_config_parse_tables(const efi_config_table_t *config_tables,
> +				   int count,
> +				   const efi_config_table_type_t *arch_tables);
>  extern int efi_systab_check_header(const efi_table_hdr_t *systab_hdr,
>  				   int min_major_version);
>  extern void efi_systab_report_header(const efi_table_hdr_t *systab_hdr,
> -- 
> 2.17.1
>