Re: [PATCH] efi: Include a .bss section within the PE/COFF headers

[Michael Brown <mbrown-OViyBiuKJBuK421+ScFKDQ@public.gmane.org>]

On 09/07/14 22:41, Michael Brown wrote:
> The PE/COFF headers currently describe only the initialised-data
> portions of the image, and result in no space being allocated for the
> uninitialised-data portions.  Consequently, the EFI boot stub will end
> up overwriting unexpected areas of memory, with unpredictable results.
>
> Fix by including a .bss section in the PE/COFF headers (functionally
> equivalent to the init_size field in the bzImage header).

Following on from this: hpa mentioned via IRC that we should also take 
alignment into account.  I am unsure if init_size already includes 
padding for alignment; on my sample kernel init_size is >16MB (with 16MB 
alignment), so it looks plausible to me that alignment is already 
accounted for.

If not, then the following trivial patch exposes the desired alignment 
via the PE/COFF headers:

diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 7a6d43a..16ef025 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -154,7 +154,7 @@ extra_header_fields:
  #else
  	.quad	0				# ImageBase
  #endif
-	.long	0x20				# SectionAlignment
+	.long	CONFIG_PHYSICAL_ALIGN		# SectionAlignment
  	.long	0x20				# FileAlignment
  	.word	0				# MajorOperatingSystemVersion
  	.word	0				# MinorOperatingSystemVersion
-- 
1.8.4.5

Michael