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Commit 7e8213c1 authored by Matt Fleming's avatar Matt Fleming Committed by Matt Fleming
Browse files

x86/efi: Correct EFI boot stub use of code32_start 



code32_start should point at the start of the protected mode code, and
*not* at the beginning of the bzImage. This is much easier to do in
assembly so document that callers of make_boot_params() need to fill out
code32_start.

The fallout from this bug is that we would end up relocating the image
but copying the image at some offset, resulting in what appeared to be
memory corruption.

Reported-by: default avatarThomas Bächler <thomas@archlinux.org>
Signed-off-by: default avatarMatt Fleming <matt.fleming@intel.com>
parent 396f1a08

arch/x86/boot/compressed/eboot.c

+3 −2
Original line number Diff line number Diff line
@@ -1016,6 +1016,9 @@ void setup_graphics(struct boot_params *boot_params) 
 * Because the x86 boot code expects to be passed a boot_params we

 * need to create one ourselves (usually the bootloader would create

 * one for us).

 *

 * The caller is responsible for filling out ->code32_start in the

 * returned boot_params.

 */

struct boot_params *make_boot_params(struct efi_config *c)

{
@@ -1081,8 +1084,6 @@ struct boot_params *make_boot_params(struct efi_config *c) 
	hdr->vid_mode = 0xffff;

	hdr->boot_flag = 0xAA55;



	hdr->code32_start = (__u64)(unsigned long)image->image_base;



	hdr->type_of_loader = 0x21;



	/* Convert unicode cmdline to ascii */

arch/x86/boot/compressed/head_32.S

+2 −6
Original line number Diff line number Diff line
@@ -59,6 +59,7 @@ ENTRY(efi_pe_entry) 
	call	make_boot_params

	cmpl	$0, %eax

	je	fail

	movl	%esi, BP_code32_start(%eax)

	popl	%ecx

	pushl	%eax

	pushl	%ecx
@@ -90,12 +91,7 @@ fail: 
	hlt

	jmp	fail

2:

	call	3f

3:

	popl	%eax

	subl	$3b, %eax

	subl	BP_pref_address(%esi), %eax

	add	BP_code32_start(%esi), %eax

	movl	BP_code32_start(%esi), %eax

	leal	preferred_addr(%eax), %eax

	jmp	*%eax

arch/x86/boot/compressed/head_64.S

+3 −6
Original line number Diff line number Diff line
@@ -261,6 +261,8 @@ ENTRY(efi_pe_entry) 
	cmpq	$0,%rax

	je	fail

	mov	%rax, %rsi

	leaq	startup_32(%rip), %rax

	movl	%eax, BP_code32_start(%rsi)

	jmp	2f		/* Skip the relocation */



handover_entry:
@@ -284,12 +286,7 @@ fail: 
	hlt

	jmp	fail

2:

	call	3f

3:

	popq	%rax

	subq	$3b, %rax

	subq	BP_pref_address(%rsi), %rax

	add	BP_code32_start(%esi), %eax

	movl	BP_code32_start(%esi), %eax

	leaq	preferred_addr(%rax), %rax

	jmp	*%rax