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modpost: detect endianness on run-time

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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: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
This commit is contained in:
Masahiro Yamada 2024-07-27 16:42:02 +09:00
parent 4f32f799a9
commit a660deb0f1
3 changed files with 40 additions and 28 deletions
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19
scripts/mod/mk_elfconfig.c
View File

@ -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;
}

36
scripts/mod/modpost.c
View File

@ -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);

13
scripts/mod/modpost.h
View File

@ -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);