diff options
| author | Andy Lutomirski <luto@kernel.org> | 2021-01-21 08:09:50 +0300 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2021-01-29 14:22:15 +0300 |
| commit | b0dc553cfc9d3bc2c7b8672b0b2fcf0edf0c3b6e (patch) | |
| tree | 96c4bd6d9fe44564243e63867c4c0c7e7767141e /arch/x86/include/asm/efi.h | |
| parent | 6ee1d745b7c9fd573fba142a2efdad76a9f1cb04 (diff) | |
| download | linux-b0dc553cfc9d3bc2c7b8672b0b2fcf0edf0c3b6e.tar.xz | |
x86/fpu: Make the EFI FPU calling convention explicit
EFI uses kernel_fpu_begin() to conform to the UEFI calling convention.
This specifically requires initializing FCW (FPU Control Word), whereas
no sane 64-bit kernel code should use legacy 387 operations that
reference FCW.
This should allow to safely change the default semantics of
kernel_fpu_begin() to stop initializing FCW on 64-bit kernels.
[ bp: Massage commit message a little. ]
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/25d392fff64680e0f4bb8cf0b1003314dc29eafe.1611205691.git.luto@kernel.org
Diffstat (limited to 'arch/x86/include/asm/efi.h')
| -rw-r--r-- | arch/x86/include/asm/efi.h | 24 |
1 files changed, 20 insertions, 4 deletions
diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h index c98f78330b09..c81e68f00071 100644 --- a/arch/x86/include/asm/efi.h +++ b/arch/x86/include/asm/efi.h @@ -68,17 +68,33 @@ extern unsigned long efi_fw_vendor, efi_config_table; #f " called with too many arguments (" #p ">" #n ")"); \ }) +static inline void efi_fpu_begin(void) +{ + /* + * The UEFI calling convention (UEFI spec 2.3.2 and 2.3.4) requires + * that FCW and MXCSR (64-bit) must be initialized prior to calling + * UEFI code. (Oddly the spec does not require that the FPU stack + * be empty.) + */ + kernel_fpu_begin_mask(KFPU_387 | KFPU_MXCSR); +} + +static inline void efi_fpu_end(void) +{ + kernel_fpu_end(); +} + #ifdef CONFIG_X86_32 #define arch_efi_call_virt_setup() \ ({ \ - kernel_fpu_begin(); \ + efi_fpu_begin(); \ firmware_restrict_branch_speculation_start(); \ }) #define arch_efi_call_virt_teardown() \ ({ \ firmware_restrict_branch_speculation_end(); \ - kernel_fpu_end(); \ + efi_fpu_end(); \ }) #define arch_efi_call_virt(p, f, args...) p->f(args) @@ -107,7 +123,7 @@ struct efi_scratch { #define arch_efi_call_virt_setup() \ ({ \ efi_sync_low_kernel_mappings(); \ - kernel_fpu_begin(); \ + efi_fpu_begin(); \ firmware_restrict_branch_speculation_start(); \ efi_switch_mm(&efi_mm); \ }) @@ -119,7 +135,7 @@ struct efi_scratch { ({ \ efi_switch_mm(efi_scratch.prev_mm); \ firmware_restrict_branch_speculation_end(); \ - kernel_fpu_end(); \ + efi_fpu_end(); \ }) #ifdef CONFIG_KASAN |