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| author | Matt Fleming <matt.fleming@intel.com> | 2014-01-10 15:37:17 +0000 |
|---|---|---|
| committer | Matt Fleming <matt.fleming@intel.com> | 2014-03-04 21:25:04 +0000 |
| commit | 0154416a71c2a84c3746c8dd8ed25287e36934d3 (patch) | |
| tree | 80251a960a808ee33b4822b5613b55ceec28c714 /arch/x86/boot | |
| parent | 54b52d87268034859191d671505bb1cfce6bd74d (diff) | |
| download | linux-0154416a71c2a84c3746c8dd8ed25287e36934d3.tar.gz linux-0154416a71c2a84c3746c8dd8ed25287e36934d3.tar.bz2 linux-0154416a71c2a84c3746c8dd8ed25287e36934d3.zip | |
x86/efi: Add early thunk code to go from 64-bit to 32-bit
Implement the transition code to go from IA32e mode to protected mode in
the EFI boot stub. This is required to use 32-bit EFI services from a
64-bit kernel.
Since EFI boot stub is executed in an identity-mapped region, there's
not much we need to do before invoking the 32-bit EFI boot services.
However, we do reload the firmware's global descriptor table
(efi32_boot_gdt) in case things like timer events are still running in
the firmware.
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Diffstat (limited to 'arch/x86/boot')
| -rw-r--r-- | arch/x86/boot/compressed/efi_stub_64.S | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/arch/x86/boot/compressed/efi_stub_64.S b/arch/x86/boot/compressed/efi_stub_64.S index cedc60de86eb..7ff3632806b1 100644 --- a/arch/x86/boot/compressed/efi_stub_64.S +++ b/arch/x86/boot/compressed/efi_stub_64.S @@ -1 +1,30 @@ +#include <asm/segment.h> +#include <asm/msr.h> +#include <asm/processor-flags.h> + #include "../../platform/efi/efi_stub_64.S" + +#ifdef CONFIG_EFI_MIXED + .code64 + .text +ENTRY(efi64_thunk) + push %rbp + push %rbx + + subq $16, %rsp + leaq efi_exit32(%rip), %rax + movl %eax, 8(%rsp) + leaq efi_gdt64(%rip), %rax + movl %eax, 4(%rsp) + movl %eax, 2(%rax) /* Fixup the gdt base address */ + leaq efi32_boot_gdt(%rip), %rax + movl %eax, (%rsp) + + call __efi64_thunk + + addq $16, %rsp + pop %rbx + pop %rbp + ret +ENDPROC(efi64_thunk) +#endif /* CONFIG_EFI_MIXED */ |