On 8/18/22 16:51, Ard Biesheuvel wrote:
The PE/COFF spec permits the COFF signature and file header to appear
anywhere in the file, and the actual offset is recorded in 4 byte
little endian field at offset 0x3c of the image.
When GRUB is emitted as a PE/COFF binary, we reuse the 128 byte MS-DOS
stub (even for non-x86 architectures), putting the COFF signature and
file header at offset 0x80. However, other PE/COFF images may use
different values, and non-x86 Linux kernels use an offset of 0x40
instead.
So let's get rid of the grub_pe32_header struct from pe32.h, given that
it does not represent anything defined by the PE/COFF spec. Instead,
use the GRUB_PE32_MSDOS_STUB_SIZE macro explicitly to reference the
COFF header in the only place in the code where we rely on this.
The remaining fields are moved into a struct grub_coff_image_header,
which we will use later to access COFF header fields of arbitrary
images (and which may therefore appear at different offsets)
Signed-off-by: Ard Biesheuvel <a...@kernel.org>
---
grub-core/kern/efi/efi.c | 5 +++--
include/grub/efi/pe32.h | 5 +----
2 files changed, 4 insertions(+), 6 deletions(-)
diff --git a/grub-core/kern/efi/efi.c b/grub-core/kern/efi/efi.c
index e8a976a22f15..8bef81663853 100644
--- a/grub-core/kern/efi/efi.c
+++ b/grub-core/kern/efi/efi.c
@@ -302,7 +302,7 @@ grub_addr_t
grub_efi_modules_addr (void)
{
grub_efi_loaded_image_t *image;
- struct grub_pe32_header *header;
+ struct grub_coff_image_header *header;
struct grub_pe32_coff_header *coff_header;
struct grub_pe32_section_table *sections;
struct grub_pe32_section_table *section;
@@ -313,7 +313,8 @@ grub_efi_modules_addr (void)
if (! image)
return 0;
- header = image->image_base;
+ header = (struct grub_coff_image_header *) ((char *) image->image_base
+ + GRUB_PE32_MSDOS_STUB_SIZE);
As you described above the offset to the PE-COFF header isn't a constant.
Please, cast image->image_base to struct IMAGE_DOS_HEADER * and use the
value of e_lfanew instead of GRUB_PE32_MSDOS_STUB_SIZE here.
You can copy the definjtion of struct IMAGE_DOS_HEADER from gnu-efi's
/usr/include/efi/x86_64/pe.h.
Best regards
Heinrich
coff_header = &(header->coff_header);
sections
= (struct grub_pe32_section_table *) ((char *) coff_header
diff --git a/include/grub/efi/pe32.h b/include/grub/efi/pe32.h
index 0ed8781f0376..a2da4b318c85 100644
--- a/include/grub/efi/pe32.h
+++ b/include/grub/efi/pe32.h
@@ -254,11 +254,8 @@ struct grub_pe32_section_table
#define GRUB_PE32_SIGNATURE_SIZE 4
-struct grub_pe32_header
+struct grub_coff_image_header
{
- /* This should be filled in with GRUB_PE32_MSDOS_STUB. */
- grub_uint8_t msdos_stub[GRUB_PE32_MSDOS_STUB_SIZE];
-
/* This is always PE\0\0. */
char signature[GRUB_PE32_SIGNATURE_SIZE];
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