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s390/module: fix loading modules with a lot of relocations 

If the size of the PLT entries generated by apply_rela() exceeds
64KiB, the first ones can no longer reach __jump_r1 with brc. Fix by
using brcl. An alternative solution is to add a __jump_r1 copy after
every 64KiB, however, the space savings are quite small and do not
justify the additional complexity.

Fixes: f19fbd5ed6 ("s390: introduce execute-trampolines for branches")
Cc: stable@vger.kernel.org
Reported-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Ilya Leoshkevich 2022-01-19 19:26:37 +01:00 committed by Heiko Carstens
parent 3d787b392d
commit f3b7e73b2c
1 changed files with 17 additions and 18 deletions
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35
arch/s390/kernel/module.c
View File

@ -33,7 +33,7 @@
#define DEBUGP(fmt , ...)
#endif
#define PLT_ENTRY_SIZE 20
#define PLT_ENTRY_SIZE 22
void *module_alloc(unsigned long size)
{
@ -341,27 +341,26 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
case R_390_PLTOFF32: /* 32 bit offset from GOT to PLT. */
case R_390_PLTOFF64: /* 16 bit offset from GOT to PLT. */
if (info->plt_initialized == 0) {
unsigned int insn[5];
unsigned int *ip = me->core_layout.base +
me->arch.plt_offset +
info->plt_offset;
unsigned char insn[PLT_ENTRY_SIZE];
char *plt_base;
char *ip;
insn[0] = 0x0d10e310; /* basr 1,0 */
insn[1] = 0x100a0004; /* lg 1,10(1) */
plt_base = me->core_layout.base + me->arch.plt_offset;
ip = plt_base + info->plt_offset;
*(int *)insn = 0x0d10e310; /* basr 1,0 */
*(int *)&insn[4] = 0x100c0004; /* lg 1,12(1) */
if (IS_ENABLED(CONFIG_EXPOLINE) && !nospec_disable) {
unsigned int *ij;
ij = me->core_layout.base +
me->arch.plt_offset +
me->arch.plt_size - PLT_ENTRY_SIZE;
insn[2] = 0xa7f40000 + /* j __jump_r1 */
(unsigned int)(u16)
(((unsigned long) ij - 8 -
(unsigned long) ip) / 2);
char *jump_r1;
jump_r1 = plt_base + me->arch.plt_size -
PLT_ENTRY_SIZE;
/* brcl 0xf,__jump_r1 */
*(short *)&insn[8] = 0xc0f4;
*(int *)&insn[10] = (jump_r1 - (ip + 8)) / 2;
} else {
insn[2] = 0x07f10000; /* br %r1 */
*(int *)&insn[8] = 0x07f10000; /* br %r1 */
}
insn[3] = (unsigned int) (val >> 32);
insn[4] = (unsigned int) val;
*(long *)&insn[14] = val;
write(ip, insn, sizeof(insn));
info->plt_initialized = 1;