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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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7
src/lj_asm_mips.h
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@@ -1665,6 +1665,9 @@ static void asm_stack_restore(ASMState *as, SnapShot *snap)
/* -- GC handling --------------------------------------------------------- */
/* Marker to prevent patching the GC check exit. */
#define MIPS_NOPATCH_GC_CHECK MIPSI_OR
/* Check GC threshold and do one or more GC steps. */
static void asm_gc_check(ASMState *as)
{
@@ -1680,6 +1683,7 @@ static void asm_gc_check(ASMState *as)
args[0] = ASMREF_TMP1; /* global_State *g */
args[1] = ASMREF_TMP2; /* MSize steps */
asm_gencall(as, ci, args);
l_end[-3] = MIPS_NOPATCH_GC_CHECK; /* Replace the nop after the call. */
emit_tsi(as, MIPSI_ADDIU, ra_releasetmp(as, ASMREF_TMP1), RID_JGL, -32768);
tmp = ra_releasetmp(as, ASMREF_TMP2);
emit_loadi(as, tmp, as->gcsteps);
@@ -1936,7 +1940,8 @@ void lj_asm_patchexit(jit_State *J, GCtrace *T, ExitNo exitno, MCode *target)
if (((p[-1] ^ (px-p)) & 0xffffu) == 0 &&
((p[-1] & 0xf0000000u) == MIPSI_BEQ ||
(p[-1] & 0xfc1e0000u) == MIPSI_BLTZ ||
(p[-1] & 0xffe00000u) == MIPSI_BC1F)) {
(p[-1] & 0xffe00000u) == MIPSI_BC1F) &&
p[-2] != MIPS_NOPATCH_GC_CHECK) {
ptrdiff_t delta = target - p;
if (((delta + 0x8000) >> 16) == 0) { /* Patch in-range branch. */
patchbranch: