From b8ff87a6158886771677e6dc8139bac6e3cba717 Mon Sep 17 00:00:00 2001 From: Matt Fleming Date: Fri, 10 Jan 2014 15:54:31 +0000 Subject: x86/efi: Firmware agnostic handover entry points The EFI handover code only works if the "bitness" of the firmware and the kernel match, i.e. 64-bit firmware and 64-bit kernel - it is not possible to mix the two. This goes against the tradition that a 32-bit kernel can be loaded on a 64-bit BIOS platform without having to do anything special in the boot loader. Linux distributions, for one thing, regularly run only 32-bit kernels on their live media. Despite having only one 'handover_offset' field in the kernel header, EFI boot loaders use two separate entry points to enter the kernel based on the architecture the boot loader was compiled for, (1) 32-bit loader: handover_offset (2) 64-bit loader: handover_offset + 512 Since we already have two entry points, we can leverage them to infer the bitness of the firmware we're running on, without requiring any boot loader modifications, by making (1) and (2) valid entry points for both CONFIG_X86_32 and CONFIG_X86_64 kernels. To be clear, a 32-bit boot loader will always use (1) and a 64-bit boot loader will always use (2). It's just that, if a single kernel image supports (1) and (2) that image can be used with both 32-bit and 64-bit boot loaders, and hence both 32-bit and 64-bit EFI. (1) and (2) must be 512 bytes apart at all times, but that is already part of the boot ABI and we could never change that delta without breaking existing boot loaders anyhow. Signed-off-by: Matt Fleming --- arch/x86/include/asm/efi.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'arch/x86/include/asm/efi.h') diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h index 3d6b9f81cc68..85856868507b 100644 --- a/arch/x86/include/asm/efi.h +++ b/arch/x86/include/asm/efi.h @@ -19,9 +19,11 @@ */ #define EFI_OLD_MEMMAP EFI_ARCH_1 +#define EFI32_LOADER_SIGNATURE "EL32" +#define EFI64_LOADER_SIGNATURE "EL64" + #ifdef CONFIG_X86_32 -#define EFI_LOADER_SIGNATURE "EL32" extern unsigned long asmlinkage efi_call_phys(void *, ...); @@ -57,8 +59,6 @@ extern unsigned long asmlinkage efi_call_phys(void *, ...); #else /* !CONFIG_X86_32 */ -#define EFI_LOADER_SIGNATURE "EL64" - extern u64 efi_call0(void *fp); extern u64 efi_call1(void *fp, u64 arg1); extern u64 efi_call2(void *fp, u64 arg1, u64 arg2); -- cgit v1.2.1 From 4f9dbcfc40299ddaa780fe8c1cd74998c1be3af5 Mon Sep 17 00:00:00 2001 From: Matt Fleming Date: Fri, 10 Jan 2014 18:48:30 +0000 Subject: x86/efi: Add mixed runtime services support Setup the runtime services based on whether we're booting in EFI native mode or not. For non-native mode we need to thunk from 64-bit into 32-bit mode before invoking the EFI runtime services. Using the runtime services after SetVirtualAddressMap() is slightly more complicated because we need to ensure that all the addresses we pass to the firmware are below the 4GB boundary so that they can be addressed with 32-bit pointers, see efi_setup_page_tables(). Signed-off-by: Matt Fleming --- arch/x86/include/asm/efi.h | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'arch/x86/include/asm/efi.h') diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h index 85856868507b..85935e6f69f3 100644 --- a/arch/x86/include/asm/efi.h +++ b/arch/x86/include/asm/efi.h @@ -154,6 +154,27 @@ static inline bool efi_is_native(void) extern struct console early_efi_console; extern void parse_efi_setup(u64 phys_addr, u32 data_len); + +#ifdef CONFIG_EFI_MIXED +extern void efi_thunk_runtime_setup(void); +extern efi_status_t efi_thunk_set_virtual_address_map( + void *phys_set_virtual_address_map, + unsigned long memory_map_size, + unsigned long descriptor_size, + u32 descriptor_version, + efi_memory_desc_t *virtual_map); +#else +static inline void efi_thunk_runtime_setup(void) {} +static inline efi_status_t efi_thunk_set_virtual_address_map( + void *phys_set_virtual_address_map, + unsigned long memory_map_size, + unsigned long descriptor_size, + u32 descriptor_version, + efi_memory_desc_t *virtual_map) +{ + return EFI_SUCCESS; +} +#endif /* CONFIG_EFI_MIXED */ #else /* * IF EFI is not configured, have the EFI calls return -ENOSYS. -- cgit v1.2.1 From 7d453eee36ae4cf30fc2f2faae54f634c4f863b7 Mon Sep 17 00:00:00 2001 From: Matt Fleming Date: Fri, 10 Jan 2014 18:52:06 +0000 Subject: x86/efi: Wire up CONFIG_EFI_MIXED Add the Kconfig option and bump the kernel header version so that boot loaders can check whether the handover code is available if they want. The xloadflags field in the bzImage header is also updated to reflect that the kernel supports both entry points by setting both of XLF_EFI_HANDOVER_32 and XLF_EFI_HANDOVER_64 when CONFIG_EFI_MIXED=y. XLF_CAN_BE_LOADED_ABOVE_4G is disabled so that the kernel text is guaranteed to be addressable with 32-bits. Note that no boot loaders should be using the bits set in xloadflags to decide which entry point to jump to. The entire scheme is based on the concept that 32-bit bootloaders always jump to ->handover_offset and 64-bit loaders always jump to ->handover_offset + 512. We set both bits merely to inform the boot loader that it's safe to use the native handover offset even if the machine type in the PE/COFF header claims otherwise. Signed-off-by: Matt Fleming --- arch/x86/include/asm/efi.h | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'arch/x86/include/asm/efi.h') diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h index 85935e6f69f3..a3837254e320 100644 --- a/arch/x86/include/asm/efi.h +++ b/arch/x86/include/asm/efi.h @@ -152,6 +152,17 @@ static inline bool efi_is_native(void) return IS_ENABLED(CONFIG_X86_64) == efi_enabled(EFI_64BIT); } +static inline bool efi_runtime_supported(void) +{ + if (efi_is_native()) + return true; + + if (IS_ENABLED(CONFIG_EFI_MIXED) && !efi_enabled(EFI_OLD_MEMMAP)) + return true; + + return false; +} + extern struct console early_efi_console; extern void parse_efi_setup(u64 phys_addr, u32 data_len); -- cgit v1.2.1