efi/x86: add headroom to decompressor BSS to account for setup block

In the bootparams struct, init_size defines the static footprint of the
bzImage, counted from the start of the kernel image, i.e., startup_32().

The PE/COFF metadata declares the same size for the entire image, but this
time, the image includes the setup block as well, and so the space reserved
by UEFI is a bit too small. This usually doesn't matter, since we normally
relocate the kernel into a memory allocation of the correct size.
But in the unlikely case that the image happens to be loaded at exactly
the preferred offset, we skip this relocation, and execute the image in
place, stepping on memory beyond the provided allocation, which may be
in use for other purposes.

Let's fix this by adding the size of the setup block to the image size as
declared in the PE/COFF header.

Signed-off-by: Ard Biesheuvel <[email protected]>

diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c
index 55e669d29e54fc369cdac1baf48d3f0e26f126c0..c08db2ee4ba27e2571f090804139ef973b2a18f8 100644 (file)
--- a/arch/x86/boot/tools/build.c
+++ b/arch/x86/boot/tools/build.c
@@ -408,7 +408,7 @@ int main(int argc, char ** argv)
 
        update_pecoff_text(setup_sectors * 512, i + (sys_size * 16));
        init_sz = get_unaligned_le32(&buf[0x260]);
-       update_pecoff_bss(i + (sys_size * 16), init_sz);
+       update_pecoff_bss(i + (sys_size * 16), init_sz + setup_sectors * 512);
 
        efi_stub_entry_update();