Commit 8acf63ef authored by Arvind Sankar's avatar Arvind Sankar Committed by Ingo Molnar
Browse files

efi/x86: Avoid using code32_start 



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: default avatarArvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarIngo 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
parent 3fab4331

arch/x86/boot/compressed/head_32.S

+1 −2
Original line number Diff line number Diff line
@@ -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)

arch/x86/boot/compressed/head_64.S

+2 −2
Original line number Diff line number Diff line
@@ -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)

arch/x86/kernel/asm-offsets.c

+0 −1
Original line number Diff line number Diff line
@@ -88,7 +88,6 @@ static void __used common(void) 
	OFFSET(BP_kernel_alignment, boot_params, hdr.kernel_alignment);

	OFFSET(BP_init_size, boot_params, hdr.init_size);

	OFFSET(BP_pref_address, boot_params, hdr.pref_address);

	OFFSET(BP_code32_start, boot_params, hdr.code32_start);



	BLANK();

	DEFINE(PTREGS_SIZE, sizeof(struct pt_regs));

drivers/firmware/efi/libstub/x86-stub.c

+5 −5
Original line number Diff line number Diff line
@@ -703,10 +703,11 @@ static efi_status_t exit_boot(struct boot_params *boot_params, void *handle) 
}



/*

 * On success we return a pointer to a boot_params structure, and NULL

 * on failure.

 * On success, we return the address of startup_32, which has potentially been

 * relocated by efi_relocate_kernel.

 * On failure, we exit to the firmware via efi_exit instead of returning.

 */

struct boot_params *efi_main(efi_handle_t handle,

unsigned long efi_main(efi_handle_t handle,

			     efi_system_table_t *sys_table_arg,

			     struct boot_params *boot_params)

{
@@ -736,7 +737,6 @@ struct boot_params *efi_main(efi_handle_t handle, 
			goto fail;

		}

	}

	hdr->code32_start = (u32)bzimage_addr;



	/*

	 * efi_pe_entry() may have been called before efi_main(), in which
@@ -799,7 +799,7 @@ struct boot_params *efi_main(efi_handle_t handle, 
		goto fail;

	}



	return boot_params;

	return bzimage_addr;

fail:

	efi_printk("efi_main() failed!\n");

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