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Prevent patching of the GC exit check branch.

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Reported by Arseny Vakhrushev.
This commit is contained in:
Mike Pall
2020-09-27 16:44:13 +02:00
parent 881d02d311
commit e8ec6fe996
4 changed files with 31 additions and 7 deletions
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11
src/lj_asm_x86.h
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@@ -2884,6 +2884,7 @@ void lj_asm_patchexit(jit_State *J, GCtrace *T, ExitNo exitno, MCode *target)
MSize len = T->szmcode;
MCode *px = exitstub_addr(J, exitno) - 6;
MCode *pe = p+len-6;
MCode *pgc = NULL;
uint32_t stateaddr = u32ptr(&J2G(J)->vmstate);
if (len > 5 && p[len-5] == XI_JMP && p+len-6 + *(int32_t *)(p+len-4) == px)
*(int32_t *)(p+len-4) = jmprel(p+len, target);
@@ -2892,9 +2893,15 @@ void lj_asm_patchexit(jit_State *J, GCtrace *T, ExitNo exitno, MCode *target)
if (*(uint32_t *)(p+(LJ_64 ? 3 : 2)) == stateaddr && p[0] == XI_MOVmi)
break;
lua_assert(p < pe);
for (; p < pe; p += asm_x86_inslen(p))
if ((*(uint16_t *)p & 0xf0ff) == 0x800f && p + *(int32_t *)(p+2) == px)
for (; p < pe; p += asm_x86_inslen(p)) {
if ((*(uint16_t *)p & 0xf0ff) == 0x800f && p + *(int32_t *)(p+2) == px &&
p != pgc) {
*(int32_t *)(p+2) = jmprel(p+6, target);
} else if (*p == XI_CALL &&
(void *)(p+5+*(int32_t *)(p+1)) == (void *)lj_gc_step_jit) {
pgc = p+7; /* Do not patch GC check exit. */
}
}
lj_mcode_sync(T->mcode, T->mcode + T->szmcode);
lj_mcode_patch(J, mcarea, 1);
}