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x86/efi: Correct EFI boot stub use of code32_start

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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: Thomas Bächler <thomas@archlinux.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
This commit is contained in:
Matt Fleming 2014-04-08 13:14:00 +01:00 committed by Matt Fleming
parent 396f1a08db
commit 7e8213c1f3
3 changed files with 8 additions and 14 deletions
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5
arch/x86/boot/compressed/eboot.c
View file

@ -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 */

8
arch/x86/boot/compressed/head_32.S
View file

@ -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

9
arch/x86/boot/compressed/head_64.S
View file

@ -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