DrSocalkwe3n/luajit
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Prevent patching of the GC exit check branch.

Browse Source 
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
Download Patch File Download Diff File Expand all files Collapse all files

13
src/lj_asm_ppc.h
View File

@@ -1852,6 +1852,9 @@ static void asm_stack_restore(ASMState *as, SnapShot *snap)
/* -- GC handling --------------------------------------------------------- */
/* Marker to prevent patching the GC check exit. */
#define PPC_NOPATCH_GC_CHECK PPCI_ORIS
/* Check GC threshold and do one or more GC steps. */
static void asm_gc_check(ASMState *as)
{
@@ -1863,6 +1866,7 @@ static void asm_gc_check(ASMState *as)
l_end = emit_label(as);
/* Exit trace if in GCSatomic or GCSfinalize. Avoids syncing GC objects. */
asm_guardcc(as, CC_NE); /* Assumes asm_snap_prep() already done. */
*--as->mcp = PPC_NOPATCH_GC_CHECK;
emit_ai(as, PPCI_CMPWI, RID_RET, 0);
args[0] = ASMREF_TMP1; /* global_State *g */
args[1] = ASMREF_TMP2; /* MSize steps */
@@ -2124,7 +2128,7 @@ void lj_asm_patchexit(jit_State *J, GCtrace *T, ExitNo exitno, MCode *target)
MCode *px = exitstub_trace_addr(T, exitno);
MCode *cstart = NULL;
MCode *mcarea = lj_mcode_patch(J, p, 0);
int clearso = 0;
int clearso = 0, patchlong = 1;
for (; p < pe; p++) {
/* Look for exitstub branch, try to replace with branch to target. */
uint32_t ins = *p;
@@ -2136,7 +2140,9 @@ void lj_asm_patchexit(jit_State *J, GCtrace *T, ExitNo exitno, MCode *target)
delta -= sizeof(MCode);
}
/* Many, but not all short-range branches can be patched directly. */
if (((delta + 0x8000) >> 16) == 0) {
if (p[-1] == PPC_NOPATCH_GC_CHECK) {
patchlong = 0;
} else if (((delta + 0x8000) >> 16) == 0) {
*p = (ins & 0xffdf0000u) | ((uint32_t)delta & 0xffffu) |
((delta & 0x8000) * (PPCF_Y/0x8000));
if (!cstart) cstart = p;
@@ -2149,7 +2155,8 @@ void lj_asm_patchexit(jit_State *J, GCtrace *T, ExitNo exitno, MCode *target)
if (!cstart) cstart = p;
}
}
{ /* Always patch long-range branch in exit stub itself. */
/* Always patch long-range branch in exit stub itself. Except, if we can't. */
if (patchlong) {
ptrdiff_t delta = (char *)target - (char *)px - clearso;
lua_assert(((delta + 0x02000000) >> 26) == 0);
*px = PPCI_B | ((uint32_t)delta & 0x03ffffffu);