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modpost: work around unaligned data access error

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With the latest binutils, modpost fails with a bus error on some
architectures such as ARM and sparc64.

Since binutils commit 1f1b5e506bf0 ("bfd/ELF: restrict file alignment
for object files"), the byte offset to each section (sh_offset) in
relocatable ELF is no longer guaranteed to be aligned.

modpost parses MODULE_DEVICE_TABLE() data structures, which are usually
located in the .rodata section. If it is not properly aligned, unaligned
access errors may occur.

To address the issue, this commit imports the get_unaligned() helper
from include/linux/unaligned.h.

The get_unaligned_native() helper caters to the endianness in addition
to handling the unaligned access.

I slightly refactored do_pcmcia_entry() and do_input() to avoid writing
back to an unaligned address. (We would need the put_unaligned() helper
to do that.)

The addend_*_rel() functions need similar adjustments because the .text
sections are not aligned either.

It seems that the .symtab, .rel.* and .rela.* sections are still aligned.
Keep normal pointer access for these sections to avoid unnecessary
performance costs.

Reported-by: Paulo Pisati <paolo.pisati@canonical.com>
Reported-by: Matthias Klose <doko@debian.org>
Closes: https://sourceware.org/bugzilla/show_bug.cgi?id=32435
Reported-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Closes: https://sourceware.org/bugzilla/show_bug.cgi?id=32493
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
This commit is contained in:
Masahiro Yamada 2024-12-26 00:33:37 +09:00
parent e1352d7ead
commit 8fe1a63d3d
3 changed files with 39 additions and 25 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

26
scripts/mod/file2alias.c
View file

@ -132,7 +132,8 @@ struct devtable {
* based at address m.
*/
#define DEF_FIELD(m, devid, f) \
typeof(((struct devid *)0)->f) f = TO_NATIVE(*(typeof(f) *)((m) + OFF_##devid##_##f))
typeof(((struct devid *)0)->f) f = \
get_unaligned_native((typeof(f) *)((m) + OFF_##devid##_##f))
/* Define a variable f that holds the address of field f of struct devid
* based at address m. Due to the way typeof works, for a field of type
@ -600,7 +601,7 @@ static void do_pnp_card_entry(struct module *mod, void *symval)
static void do_pcmcia_entry(struct module *mod, void *symval)
{
char alias[256] = {};
unsigned int i;
DEF_FIELD(symval, pcmcia_device_id, match_flags);
DEF_FIELD(symval, pcmcia_device_id, manf_id);
DEF_FIELD(symval, pcmcia_device_id, card_id);
@ -609,10 +610,6 @@ static void do_pcmcia_entry(struct module *mod, void *symval)
DEF_FIELD(symval, pcmcia_device_id, device_no);
DEF_FIELD_ADDR(symval, pcmcia_device_id, prod_id_hash);
for (i=0; i<4; i++) {
(*prod_id_hash)[i] = TO_NATIVE((*prod_id_hash)[i]);
}
ADD(alias, "m", match_flags & PCMCIA_DEV_ID_MATCH_MANF_ID,
manf_id);
ADD(alias, "c", match_flags & PCMCIA_DEV_ID_MATCH_CARD_ID,
@ -623,10 +620,14 @@ static void do_pcmcia_entry(struct module *mod, void *symval)
function);
ADD(alias, "pfn", match_flags & PCMCIA_DEV_ID_MATCH_DEVICE_NO,
device_no);
ADD(alias, "pa", match_flags & PCMCIA_DEV_ID_MATCH_PROD_ID1, (*prod_id_hash)[0]);
ADD(alias, "pb", match_flags & PCMCIA_DEV_ID_MATCH_PROD_ID2, (*prod_id_hash)[1]);
ADD(alias, "pc", match_flags & PCMCIA_DEV_ID_MATCH_PROD_ID3, (*prod_id_hash)[2]);
ADD(alias, "pd", match_flags & PCMCIA_DEV_ID_MATCH_PROD_ID4, (*prod_id_hash)[3]);
ADD(alias, "pa", match_flags & PCMCIA_DEV_ID_MATCH_PROD_ID1,
get_unaligned_native(*prod_id_hash + 0));
ADD(alias, "pb", match_flags & PCMCIA_DEV_ID_MATCH_PROD_ID2,
get_unaligned_native(*prod_id_hash + 1));
ADD(alias, "pc", match_flags & PCMCIA_DEV_ID_MATCH_PROD_ID3,
get_unaligned_native(*prod_id_hash + 2));
ADD(alias, "pd", match_flags & PCMCIA_DEV_ID_MATCH_PROD_ID4,
get_unaligned_native(*prod_id_hash + 3));
module_alias_printf(mod, true, "pcmcia:%s", alias);
}
@ -654,10 +655,9 @@ static void do_input(char *alias,
{
unsigned int i;
for (i = min / BITS_PER_LONG; i < max / BITS_PER_LONG + 1; i++)
arr[i] = TO_NATIVE(arr[i]);
for (i = min; i <= max; i++)
if (arr[i / BITS_PER_LONG] & (1ULL << (i%BITS_PER_LONG)))
if (get_unaligned_native(arr + i / BITS_PER_LONG) &
(1ULL << (i % BITS_PER_LONG)))
sprintf(alias + strlen(alias), "%X,*", i);
}

24
scripts/mod/modpost.c
View file

@ -1138,9 +1138,9 @@ static Elf_Addr addend_386_rel(uint32_t *location, unsigned int r_type)
{
switch (r_type) {
case R_386_32:
return TO_NATIVE(*location);
return get_unaligned_native(location);
case R_386_PC32:
return TO_NATIVE(*location) + 4;
return get_unaligned_native(location) + 4;
}
return (Elf_Addr)(-1);
@ -1161,24 +1161,24 @@ static Elf_Addr addend_arm_rel(void *loc, Elf_Sym *sym, unsigned int r_type)
switch (r_type) {
case R_ARM_ABS32:
case R_ARM_REL32:
inst = TO_NATIVE(*(uint32_t *)loc);
inst = get_unaligned_native((uint32_t *)loc);
return inst + sym->st_value;
case R_ARM_MOVW_ABS_NC:
case R_ARM_MOVT_ABS:
inst = TO_NATIVE(*(uint32_t *)loc);
inst = get_unaligned_native((uint32_t *)loc);
offset = sign_extend32(((inst & 0xf0000) >> 4) | (inst & 0xfff),
15);
return offset + sym->st_value;
case R_ARM_PC24:
case R_ARM_CALL:
case R_ARM_JUMP24:
inst = TO_NATIVE(*(uint32_t *)loc);
inst = get_unaligned_native((uint32_t *)loc);
offset = sign_extend32((inst & 0x00ffffff) << 2, 25);
return offset + sym->st_value + 8;
case R_ARM_THM_MOVW_ABS_NC:
case R_ARM_THM_MOVT_ABS:
upper = TO_NATIVE(*(uint16_t *)loc);
lower = TO_NATIVE(*((uint16_t *)loc + 1));
upper = get_unaligned_native((uint16_t *)loc);
lower = get_unaligned_native((uint16_t *)loc + 1);
offset = sign_extend32(((upper & 0x000f) << 12) |
((upper & 0x0400) << 1) |
((lower & 0x7000) >> 4) |
@ -1195,8 +1195,8 @@ static Elf_Addr addend_arm_rel(void *loc, Elf_Sym *sym, unsigned int r_type)
* imm11 = lower[10:0]
* imm32 = SignExtend(S:J2:J1:imm6:imm11:'0')
*/
upper = TO_NATIVE(*(uint16_t *)loc);
lower = TO_NATIVE(*((uint16_t *)loc + 1));
upper = get_unaligned_native((uint16_t *)loc);
lower = get_unaligned_native((uint16_t *)loc + 1);
sign = (upper >> 10) & 1;
j1 = (lower >> 13) & 1;
@ -1219,8 +1219,8 @@ static Elf_Addr addend_arm_rel(void *loc, Elf_Sym *sym, unsigned int r_type)
* I2 = NOT(J2 XOR S)
* imm32 = SignExtend(S:I1:I2:imm10:imm11:'0')
*/
upper = TO_NATIVE(*(uint16_t *)loc);
lower = TO_NATIVE(*((uint16_t *)loc + 1));
upper = get_unaligned_native((uint16_t *)loc);
lower = get_unaligned_native((uint16_t *)loc + 1);
sign = (upper >> 10) & 1;
j1 = (lower >> 13) & 1;
@ -1241,7 +1241,7 @@ static Elf_Addr addend_mips_rel(uint32_t *location, unsigned int r_type)
{
uint32_t inst;
inst = TO_NATIVE(*location);
inst = get_unaligned_native(location);
switch (r_type) {
case R_MIPS_LO16:
return inst & 0xffff;

14
scripts/mod/modpost.h
View file

@ -65,6 +65,20 @@
#define TO_NATIVE(x) \
(target_is_big_endian == host_is_big_endian ? x : bswap(x))
#define __get_unaligned_t(type, ptr) ({ \
const struct { type x; } __attribute__((__packed__)) *__pptr = \
(typeof(__pptr))(ptr); \
__pptr->x; \
})
#define get_unaligned(ptr) __get_unaligned_t(typeof(*(ptr)), (ptr))
#define get_unaligned_native(ptr) \
({ \
typeof(*(ptr)) _val = get_unaligned(ptr); \
TO_NATIVE(_val); \
})
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
#define strstarts(str, prefix) (strncmp(str, prefix, strlen(prefix)) == 0)