Commit bd78c9d7 authored by Masahiro Yamada's avatar Masahiro Yamada
Browse files

modpost: define TO_NATIVE() using bswap_* functions 



The current TO_NATIVE() has some limitations:

 1) You cannot cast the argument.

 2) You cannot pass a variable marked as 'const'.

 3) Passing an array is a bug, but it is not detected.

Impelement TO_NATIVE() using bswap_*() functions. These are GNU
extensions. If we face portability issues, we can port the code from
include/uapi/linux/swab.h.

With this change, get_rel_type_and_sym() can be simplified by casting
the arguments directly.

Signed-off-by: default avatarMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: default avatarNick Desaulniers <ndesaulniers@google.com>
parent ac96a15a

scripts/mod/modpost.c

+4 −9
Original line number Diff line number Diff line
@@ -1410,15 +1410,10 @@ static void get_rel_type_and_sym(struct elf_info *elf, uint64_t r_info, 
		return;

	}



	if (is_64bit) {

		Elf64_Xword r_info64 = r_info;



		r_info = TO_NATIVE(r_info64);

	} else {

		Elf32_Word r_info32 = r_info;



		r_info = TO_NATIVE(r_info32);

	}

	if (is_64bit)

		r_info = TO_NATIVE((Elf64_Xword)r_info);

	else

		r_info = TO_NATIVE((Elf32_Word)r_info);



	*r_type = ELF_R_TYPE(r_info);

	*r_sym = ELF_R_SYM(r_info);

scripts/mod/modpost.h

+12 −13
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

#include <byteswap.h>

#include <stdbool.h>

#include <stdio.h>

#include <stdlib.h>
@@ -51,22 +52,20 @@ 
#define ELF_R_TYPE  ELF64_R_TYPE

#endif



#if KERNEL_ELFDATA != HOST_ELFDATA



static inline void __endian(const void *src, void *dest, unsigned int size)

{

	unsigned int i;

	for (i = 0; i < size; i++)

		((unsigned char*)dest)[i] = ((unsigned char*)src)[size - i-1];

}



#define TO_NATIVE(x)						\

#define bswap(x) \

({ \

	typeof(x) __x;						\

	__endian(&(x), &(__x), sizeof(__x));			\

	__x;							\

	_Static_assert(sizeof(x) == 1 || sizeof(x) == 2 || \

		       sizeof(x) == 4 || sizeof(x) == 8, "bug"); \

	(typeof(x))(sizeof(x) == 2 ? bswap_16(x) : \

		    sizeof(x) == 4 ? bswap_32(x) : \

		    sizeof(x) == 8 ? bswap_64(x) : \

		    x); \

})



#if KERNEL_ELFDATA != HOST_ELFDATA



#define TO_NATIVE(x) (bswap(x))



#else /* endianness matches */



#define TO_NATIVE(x) (x)