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author | Andy Lutomirski <luto@kernel.org> | 2021-01-20 21:09:50 -0800 |
---|---|---|
committer | Borislav Petkov <bp@suse.de> | 2021-01-29 12:22:15 +0100 |
commit | b0dc553cfc9d3bc2c7b8672b0b2fcf0edf0c3b6e (patch) | |
tree | 96c4bd6d9fe44564243e63867c4c0c7e7767141e | |
parent | 6ee1d745b7c9fd573fba142a2efdad76a9f1cb04 (diff) | |
download | linux-b0dc553cfc9d3bc2c7b8672b0b2fcf0edf0c3b6e.tar.bz2 |
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
-rw-r--r-- | arch/x86/include/asm/efi.h | 24 | ||||
-rw-r--r-- | arch/x86/platform/efi/efi_64.c | 4 |
2 files changed, 22 insertions, 6 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 diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c index e1e8d4e3a213..cf7b3bfe1a1e 100644 --- a/arch/x86/platform/efi/efi_64.c +++ b/arch/x86/platform/efi/efi_64.c @@ -850,7 +850,7 @@ efi_set_virtual_address_map(unsigned long memory_map_size, virtual_map); efi_switch_mm(&efi_mm); - kernel_fpu_begin(); + efi_fpu_begin(); /* Disable interrupts around EFI calls: */ local_irq_save(flags); @@ -859,7 +859,7 @@ efi_set_virtual_address_map(unsigned long memory_map_size, descriptor_version, virtual_map); local_irq_restore(flags); - kernel_fpu_end(); + efi_fpu_end(); /* grab the virtually remapped EFI runtime services table pointer */ efi.runtime = READ_ONCE(systab->runtime); |