Commit a660deb0 authored by Masahiro Yamada's avatar Masahiro Yamada
Browse files

modpost: detect endianness on run-time 



Endianness is currently detected on compile-time, but we can defer this
until run-time. This change avoids re-executing scripts/mod/mk_elfconfig
even if modpost in the linux-headers package needs to be rebuilt for a
foreign architecture.

Signed-off-by: default avatarMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: default avatarNicolas Schier <nicolas@fjasle.eu>
parent 4f32f799

scripts/mod/mk_elfconfig.c

+0 −19
Original line number Diff line number Diff line
@@ -8,7 +8,6 @@ int 
main(int argc, char **argv)

{

	unsigned char ei[EI_NIDENT];

	union { short s; char c[2]; } endian_test;



	if (fread(ei, 1, EI_NIDENT, stdin) != EI_NIDENT) {

		fprintf(stderr, "Error: input truncated\n");
@@ -28,24 +27,6 @@ main(int argc, char **argv) 
	default:

		exit(1);

	}

	switch (ei[EI_DATA]) {

	case ELFDATA2LSB:

		printf("#define KERNEL_ELFDATA ELFDATA2LSB\n");

		break;

	case ELFDATA2MSB:

		printf("#define KERNEL_ELFDATA ELFDATA2MSB\n");

		break;

	default:

		exit(1);

	}



	endian_test.s = 0x0102;

	if (memcmp(endian_test.c, "\x01\x02", 2) == 0)

		printf("#define HOST_ELFDATA ELFDATA2MSB\n");

	else if (memcmp(endian_test.c, "\x02\x01", 2) == 0)

		printf("#define HOST_ELFDATA ELFDATA2LSB\n");

	else

		exit(1);



	return 0;

}

scripts/mod/modpost.c

+36 −0
Original line number Diff line number Diff line
@@ -50,6 +50,9 @@ static bool error_occurred; 


static bool extra_warn;



bool target_is_big_endian;

bool host_is_big_endian;



/*

 * Cut off the warnings when there are too many. This typically occurs when

 * vmlinux is missing. ('make modules' without building vmlinux.)
@@ -438,6 +441,18 @@ static int parse_elf(struct elf_info *info, const char *filename) 
		/* Not an ELF file - silently ignore it */

		return 0;

	}



	switch (hdr->e_ident[EI_DATA]) {

	case ELFDATA2LSB:

		target_is_big_endian = false;

		break;

	case ELFDATA2MSB:

		target_is_big_endian = true;

		break;

	default:

		fatal("target endian is unknown\n");

	}



	/* Fix endianness in ELF header */

	hdr->e_type      = TO_NATIVE(hdr->e_type);

	hdr->e_machine   = TO_NATIVE(hdr->e_machine);
@@ -2117,6 +2132,25 @@ struct dump_list { 
	const char *file;

};



static void check_host_endian(void)

{

	static const union {

		short s;

		char c[2];

	} endian_test = { .c = {0x01, 0x02} };



	switch (endian_test.s) {

	case 0x0102:

		host_is_big_endian = true;

		break;

	case 0x0201:

		host_is_big_endian = false;

		break;

	default:

		fatal("Unknown host endian\n");

	}

}



int main(int argc, char **argv)

{

	struct module *mod;
@@ -2181,6 +2215,8 @@ int main(int argc, char **argv) 
		}

	}



	check_host_endian();



	list_for_each_entry_safe(dl, dl2, &dump_lists, list) {

		read_dump(dl->file);

		list_del(&dl->list);

scripts/mod/modpost.h

+4 −9
Original line number Diff line number Diff line
@@ -62,15 +62,8 @@ 
		    x); \

})



#if KERNEL_ELFDATA != HOST_ELFDATA



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



#else /* endianness matches */



#define TO_NATIVE(x) (x)



#endif

#define TO_NATIVE(x)	\

	(target_is_big_endian == host_is_big_endian ? x : bswap(x))



#define NOFAIL(ptr)   do_nofail((ptr), #ptr)
@@ -187,6 +180,8 @@ void add_moddevtable(struct buffer *buf, struct module *mod); 
void get_src_version(const char *modname, char sum[], unsigned sumlen);



/* from modpost.c */

extern bool target_is_big_endian;

extern bool host_is_big_endian;

char *read_text_file(const char *filename);

char *get_line(char **stringp);

void *sym_get_data(const struct elf_info *info, const Elf_Sym *sym);