/* Free all MCode areas. */
void lj_mcode_free(jit_State *J)
{
MCode *mc = J->mcarea;
J->mcarea = NULL;
J->szallmcarea = 0;
while (mc) {
MCode *next = ((MCLink *)mc)->next;
mcode_free(J, mc, ((MCLink *)mc)->size);
mc = next;
}
}
/* All memory addresses are reachable by relative jumps. */
static void *mcode_alloc(jit_State *J, size_t sz)
{
#ifdef __OpenBSD__
/* Allow better executable memory allocation for OpenBSD W^X mode. */
void *p = mcode_alloc_at(J, 0, sz, MCPROT_RUN);
if (p && mcode_setprot(p, sz, MCPROT_GEN)) {
mcode_free(J, p, sz);
return NULL;
}
return p;
#else
return mcode_alloc_at(J, 0, sz, MCPROT_GEN);
#endif
}
/* Link generated code. Return mcode address, size and status. */
int luaJIT_link(jit_State *J, void **mcodep, size_t *szp)
{
size_t sz;
void *mcode;
/* Pass 2: link sections. */
if ((J->dasmstatus = dasm_link(Dst, &sz))) return JIT_S_DASM_ERROR;
/* Check for hardcoded limit on mcode size. */
if (sz > LUAJIT_LIM_MCODE) return JIT_S_TOOLARGE;
/* TODO: mark mcode readonly when we're done. */
mcode = mcode_alloc(J, sz);
/* Pass 3: encode sections. */
if ((J->dasmstatus = dasm_encode(Dst, mcode))) {
mcode_free(J->L, J, mcode, sz);
return JIT_S_DASM_ERROR;
}
*mcodep = mcode;
*szp = sz;
return JIT_S_OK;
}
/* Get memory within relative jump distance of our code in 64 bit mode. */
static void *mcode_alloc(jit_State *J, size_t sz)
{
/* Target an address in the static assembler code (64K aligned).
** Try addresses within a distance of target-range/2+1MB..target+range/2-1MB.
** Use half the jump range so every address in the range can reach any other.
*/
#if LJ_TARGET_MIPS
/* Use the middle of the 256MB-aligned region. */
uintptr_t target = ((uintptr_t)(void *)lj_vm_exit_handler & 0xf0000000u) +
0x08000000u;
#else
uintptr_t target = (uintptr_t)(void *)lj_vm_exit_handler & ~(uintptr_t)0xffff;
#endif
const uintptr_t range = (1u << (LJ_TARGET_JUMPRANGE-1)) - (1u << 21);
/* First try a contiguous area below the last one. */
uintptr_t hint = J->mcarea ? (uintptr_t)J->mcarea - sz : 0;
int i;
/* Limit probing iterations, depending on the available pool size. */
for (i = 0; i < LJ_TARGET_JUMPRANGE; i++) {
if (mcode_validptr(hint)) {
void *p = mcode_alloc_at(J, hint, sz, MCPROT_GEN);
if (mcode_validptr(p) &&
((uintptr_t)p + sz - target < range || target - (uintptr_t)p < range))
return p;
if (p) mcode_free(J, p, sz); /* Free badly placed area. */
}
/* Next try probing 64K-aligned pseudo-random addresses. */
do {
hint = LJ_PRNG_BITS(J, LJ_TARGET_JUMPRANGE-16) << 16;
} while (!(hint + sz < range+range));
hint = target + hint - range;
}
lj_trace_err(J, LJ_TRERR_MCODEAL); /* Give up. OS probably ignores hints? */
return NULL;
}
