[PATCH 3.12 078/182] x86/efi: Correct EFI boot stub use of code32_start

Jiri Slaby
2014-05-13T09:45:28Z

From: Matt Fleming <matt@console-pimps.org>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

commit 7e8213c1f3acc064aef37813a39f13cbfe7c3ce7 upstream.

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>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
arch/x86/boot/compressed/eboot.c | 5 +++--
arch/x86/boot/compressed/head_32.S | 14 ++++++++------
arch/x86/boot/compressed/head_64.S | 9 +++------
3 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index b7388a425f09..9b883a89aad5 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -865,6 +865,9 @@ fail:
* 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(void *handle, efi_system_table_t *_table)
{
@@ -921,8 +924,6 @@ struct boot_params *make_boot_params(void *handle, efi_system_table_t *_table)
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 */
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 5d6f6891b188..b1bd969e26aa 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -50,6 +50,13 @@ ENTRY(efi_pe_entry)
pushl %eax
pushl %esi
pushl %ecx
+
+ call reloc
+reloc:
+ popl %ecx
+ subl reloc, %ecx
+ movl %ecx, BP_code32_start(%eax)
+
sub $0x4, %esp

ENTRY(efi_stub_entry)
@@ -63,12 +70,7 @@ ENTRY(efi_stub_entry)
hlt
jmp 1b
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

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index c337422b575d..a55840367359 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -215,6 +215,8 @@ ENTRY(efi_pe_entry)
cmpq $0,%rax
je 1f
mov %rax, %rdx
+ leaq startup_32(%rip), %rax
+ movl %eax, BP_code32_start(%rdx)
popq %rsi
popq %rdi

@@ -228,12 +230,7 @@ ENTRY(efi_stub_entry)
hlt
jmp 1b
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

--
1.9.3