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efi/x86: Avoid using code32_start

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code32_start is meant for 16-bit real-mode bootloaders to inform the
kernel where the 32-bit protected mode code starts. Nothing in the
protected mode kernel except the EFI stub uses it.

efi_main() currently returns boot_params, with code32_start set inside it
to tell efi_stub_entry() where startup_32 is located. Since it was invoked
by efi_stub_entry() in the first place, boot_params is already known.
Return the address of startup_32 instead.

This will allow a 64-bit kernel to live above 4Gb, for example, and it's
cleaner as well.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200301230436.2246909-5-nivedita@alum.mit.edu
Link: https://lore.kernel.org/r/20200308080859.21568-13-ardb@kernel.org
This commit is contained in:
Arvind Sankar
2020-03-08 09:08:43 +01:00
committed by Ingo Molnar
parent 3fab43318f
commit 8acf63efa1
4 changed files with 8 additions and 10 deletions
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3
arch/x86/boot/compressed/head_32.S
View File

@@ -156,9 +156,8 @@ SYM_FUNC_END(startup_32)
SYM_FUNC_START(efi32_stub_entry)
SYM_FUNC_START_ALIAS(efi_stub_entry)
add $0x4, %esp
movl 8(%esp), %esi /* save boot_params pointer */
call efi_main
movl %eax, %esi
movl BP_code32_start(%esi), %eax
leal startup_32(%eax), %eax
jmp *%eax
SYM_FUNC_END(efi32_stub_entry)

4
arch/x86/boot/compressed/head_64.S
View File

@@ -472,9 +472,9 @@ SYM_CODE_END(startup_64)
SYM_FUNC_START(efi64_stub_entry)
SYM_FUNC_START_ALIAS(efi_stub_entry)
and $~0xf, %rsp /* realign the stack */
movq %rdx, %rbx /* save boot_params pointer */
call efi_main
movq %rax,%rsi
movl BP_code32_start(%esi), %eax
movq %rbx,%rsi
leaq startup_64(%rax), %rax
jmp *%rax
SYM_FUNC_END(efi64_stub_entry)