Function patchJump

src/e9patch/e9tactics.cpp:326–364

* Patch in a jmpq instruction. */

 * Patch in a jmpq instruction.
 */
static void patchJump(Patch *P, unsigned offset)
{
    assert(offset <= PATCH_MAX - JMP_SIZE);
    assert(offset < P->I->size);
    assert(P->A != nullptr);
     
    intptr_t diff = (P->A->lb + P->A->entry) -
        (P->I->addr + offset + JMP_SIZE);
    assert(diff >= INT32_MIN && diff <= INT32_MAX);
    int32_t rel32 = (int32_t)diff;
    
    uint8_t *bytes = P->I->PATCH + offset,
            *state = P->I->STATE + offset;
    assert(*state == STATE_INSTRUCTION || *state == STATE_FREE);
    *bytes++ = /*jmpq opcode=*/0xE9;
    *state++ = STATE_PATCHED;
    offset++;

    const uint8_t *rel32p8 = (uint8_t *)&rel32;
    unsigned i = 0;
    for (; i < sizeof(rel32) && offset + i < P->I->size; i++)
    {
        assert(state[i] == STATE_INSTRUCTION || state[i] == STATE_FREE ||
            (state[i] == STATE_PATCHED && bytes[i] == rel32p8[i]));
        bytes[i] = rel32p8[i];
        state[i] = STATE_PATCHED;
    }
    for (; i < sizeof(rel32); i++)
    {
        assert(state[i] != STATE_QUEUED);
        if (state[i] == STATE_FREE)
        {
            bytes[i] = rel32p8[i];
            state[i] = STATE_PATCHED;
        }
        else
            state[i] |= STATE_LOCKED;
    }
}

/*
 * Patch in a short jmp instruction.