void Shade::detour(void *address, void *target, void *&trampoline)
{
const size_t instr_max = 17;
auto list = instrlist_create(dr);
byte instr_data[instr_max];
byte *current = (byte *)address;
byte *min_pos = (byte *)address + 5;
size_t size = 0;
while(current < min_pos)
{
read(current, instr_data, instr_max);
auto instr = instr_create(dr);
byte *decoded = decode_from_copy(dr, instr_data, current, instr);
if(!decoded)
error("Unknown instruction");
instrlist_append(list, instr);
instr_make_persistent(dr, instr);
current += (size_t)(decoded - instr_data);
size += instr_length(dr, instr);
}
auto instr = INSTR_CREATE_jmp(dr, opnd_create_pc(current));
size += instr_length(dr, instr);
instrlist_append(list, instr);
auto local_trampoline = alloca(size);
if(!local_trampoline)
error("Out of memory");
void *remote = code_section.allocate(size, 4);
if(!instrlist_encode_to_copy(dr, list, (byte *)local_trampoline, (byte *)remote, 0, true))
error("Unable to encode instructions");
instrlist_clear_and_destroy(dr, list);
write(remote, local_trampoline, size);
trampoline = remote;
char code[5];
DWORD offset = (size_t)target - (size_t)address - 5;
code[0] = 0xE9;
*(DWORD *)(code + 1) = offset;
access(address, 5, [&] {
write(address, code, 5);
});
}
byte *
instrlist_encode(dcontext_t *dcontext, instrlist_t *ilist, byte *pc,
bool has_instr_jmp_targets)
{
return instrlist_encode_to_copy(dcontext, ilist, pc, pc, NULL, has_instr_jmp_targets);
}
