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efi/libstub/x86: Avoid globals to store context during mixed mode calls

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Instead of storing the return address in a global variable when calling
a 32-bit EFI service from the 64-bit stub, avoid the indirection via
efi_exit32, and take the return address from the stack.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Borislav Petkov <bp@alien8.de>
Cc: James Morse <james.morse@arm.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20191224151025.32482-26-ardb@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ard Biesheuvel 2019-12-24 16:10:25 +01:00 committed by Ingo Molnar
parent 7d4e323d02
commit 0679715e71
1 changed files with 3 additions and 14 deletions
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17
arch/x86/boot/compressed/efi_thunk_64.S
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@ -10,7 +10,7 @@
* needs to be able to service interrupts.
*
* On the plus side, we don't have to worry about mangling 64-bit
* addresses into 32-bits because we're executing with an identify
* addresses into 32-bits because we're executing with an identity
* mapped pagetable and haven't transitioned to 64-bit virtual addresses
* yet.
*/
@ -28,7 +28,7 @@ SYM_FUNC_START(efi64_thunk)
push %rbx
subq $8, %rsp
leaq efi_exit32(%rip), %rax
leaq 1f(%rip), %rax
movl %eax, 4(%rsp)
leaq efi_gdt64(%rip), %rax
movl %eax, (%rsp)
@ -55,9 +55,6 @@ SYM_FUNC_START(efi64_thunk)
sgdt save_gdt(%rip)
leaq 1f(%rip), %rbx
movq %rbx, func_rt_ptr(%rip)
/*
* Switch to gdt with 32-bit segments. This is the firmware GDT
* that was installed when the kernel started executing. This
@ -72,6 +69,7 @@ SYM_FUNC_START(efi64_thunk)
lretq
1: addq $32, %rsp
movq %rdi, %rax
lgdt save_gdt(%rip)
@ -99,13 +97,6 @@ SYM_FUNC_START(efi64_thunk)
ret
SYM_FUNC_END(efi64_thunk)
SYM_FUNC_START_LOCAL(efi_exit32)
movq func_rt_ptr(%rip), %rax
push %rax
mov %rdi, %rax
ret
SYM_FUNC_END(efi_exit32)
.code32
/*
* EFI service pointer must be in %edi.
@ -186,8 +177,6 @@ SYM_DATA_START_LOCAL(save_gdt)
.quad 0
SYM_DATA_END(save_gdt)
SYM_DATA_LOCAL(func_rt_ptr, .quad 0)
SYM_DATA_START(efi_gdt64)
.word efi_gdt64_end - efi_gdt64
.long 0 /* Filled out by user */