diff options
Diffstat (limited to 'arch/x86/platform/efi/efi_stub_32.S')
| -rw-r--r-- | arch/x86/platform/efi/efi_stub_32.S | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/arch/x86/platform/efi/efi_stub_32.S b/arch/x86/platform/efi/efi_stub_32.S new file mode 100644 index 000000000..f3cfdb1c9 --- /dev/null +++ b/arch/x86/platform/efi/efi_stub_32.S @@ -0,0 +1,60 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * EFI call stub for IA32. + * + * This stub allows us to make EFI calls in physical mode with interrupts + * turned off. + */ + +#include <linux/linkage.h> +#include <linux/init.h> +#include <asm/asm-offsets.h> +#include <asm/page_types.h> + + __INIT +SYM_FUNC_START(efi_call_svam) + push %ebp + movl %esp, %ebp + push %ebx + + push 16(%esp) + push 16(%esp) + push %ecx + push %edx + movl %eax, %ebx // &systab_phys->runtime + + /* + * Switch to the flat mapped alias of this routine, by jumping to the + * address of label '1' after subtracting PAGE_OFFSET from it. + */ + movl $1f, %edx + subl $__PAGE_OFFSET, %edx + jmp *%edx +1: + + /* disable paging */ + movl %cr0, %edx + andl $0x7fffffff, %edx + movl %edx, %cr0 + + /* convert the stack pointer to a flat mapped address */ + subl $__PAGE_OFFSET, %esp + + /* call the EFI routine */ + movl (%eax), %eax + call *EFI_svam(%eax) + + /* grab the virtually remapped EFI runtime services table pointer */ + movl (%ebx), %ecx + movl 36(%esp), %edx // &efi.runtime + movl %ecx, (%edx) + + /* re-enable paging */ + movl %cr0, %edx + orl $0x80000000, %edx + movl %edx, %cr0 + + movl 16(%esp), %ebx + leave + RET +SYM_FUNC_END(efi_call_svam) |