Commit 28aad1c2 authored by Sami Tolvanen's avatar Sami Tolvanen Committed by Kees Cook
Browse files

module: ensure __cfi_check alignment 

CONFIG_CFI_CLANG_SHADOW assumes the __cfi_check() function is page
aligned and at the beginning of the .text section. While Clang would
normally align the function correctly, it fails to do so for modules
with no executable code.

This change ensures the correct __cfi_check() location and
alignment. It also discards the .eh_frame section, which Clang can
generate with certain sanitizers, such as CFI.

Link: https://bugs.llvm.org/show_bug.cgi?id=46293


Signed-off-by: default avatarSami Tolvanen <samitolvanen@google.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarJessica Yu <jeyu@kernel.org>
Tested-by: default avatarNathan Chancellor <nathan@kernel.org>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210408182843.1754385-5-samitolvanen@google.com
parent 5caf9682

scripts/module.lds.S

+18 −1
Original line number Diff line number Diff line
@@ -3,10 +3,20 @@ 
 * Archs are free to supply their own linker scripts.  ld will

 * combine them automatically.

 */

#ifdef CONFIG_CFI_CLANG

# include <asm/page.h>

# define ALIGN_CFI 		ALIGN(PAGE_SIZE)

# define SANITIZER_DISCARDS	*(.eh_frame)

#else

# define ALIGN_CFI

# define SANITIZER_DISCARDS

#endif



SECTIONS {

	/DISCARD/ : {

		*(.discard)

		*(.discard.*)

		SANITIZER_DISCARDS

	}



	__ksymtab		0 : { *(SORT(___ksymtab+*)) }
@@ -41,7 +51,14 @@ SECTIONS { 
		*(.rodata..L*)

	}



	.text : { *(.text .text.[0-9a-zA-Z_]*) }

	/*

	 * With CONFIG_CFI_CLANG, we assume __cfi_check is at the beginning

	 * of the .text section, and is aligned to PAGE_SIZE.

	 */

	.text : ALIGN_CFI {

		*(.text.__cfi_check)

		*(.text .text.[0-9a-zA-Z_]* .text..L.cfi*)

	}

#endif

}