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/*
* Copyright © 2021 Willian Henrique <wsimanbrazil@yahoo.com.br>
* Copyright © 2021 Michael Smith <mikesmiffy128@gmail.com>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
* REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
* OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
* PERFORMANCE OF THIS SOFTWARE.
*/
#include <stdbool.h>
#include "con_.h"
#include "hook.h"
#include "gamedata.h"
#include "intdefs.h"
#include "mem.h"
#include "os.h"
#include "udis86.h"
#include "vcall.h"
#define SIGNONSTATE_SPAWN 5 // ready to receive entity packets
#define SIGNONSTATE_FULL 6 // fully connected, first non-delta packet receieved
typedef void (*VCALLCONV f_StopRecording)(void *);
typedef void (*VCALLCONV f_SetSignonState)(void *, int);
static void *demorecorder;
static struct con_cmd *cmd_stop;
static bool *recording;
static int *demonum;
static f_SetSignonState orig_SetSignonState;
static f_StopRecording orig_StopRecording;
static con_cmdcb orig_stop_callback;
static int auto_demonum = 1;
static bool auto_recording = false;
DEF_CVAR(sst_autorecord, "Continue recording demos through map changes",
"1", CON_ARCHIVE | CON_HIDDEN)
static void VCALLCONV hook_StopRecording(void *this) {
// This hook will get called twice per loaded save (in most games/versions,
// at least, according to SAR people): first with m_bLoadgame set to false
// and then with it set to true. This will set m_nDemoNumber to 0 and
// m_bRecording to false
orig_StopRecording(this);
if (auto_recording && con_getvari(sst_autorecord)) {
*demonum = auto_demonum;
*recording = true;
}
else {
auto_demonum = 1;
auto_recording = false;
}
}
static void VCALLCONV hook_SetSignonState(void *this, int state) {
// SIGNONSTATE_FULL *may* happen twice per load, depending on the game, so
// use SIGNONSTATE_SPAWN for demo number increase
if (state == SIGNONSTATE_SPAWN && auto_recording) auto_demonum++;
// Starting a demo recording will call this function with SIGNONSTATE_FULL
// After a load, the engine's demo recorder will only start recording when
// it reaches this state, so this is a good time to set the flag if needed
else if (state == SIGNONSTATE_FULL) {
// Changing sessions may unset the recording flag (or so says NeKzor),
// so if we want to be recording, we want to tell the engine to record.
// But also, if the engine is already recording, we want our state to
// reflect *that*. IOW, if either thing is set, also set the other one.
auto_recording |= *recording; *recording = auto_recording;
// FIXME: this will override demonum incorrectly if the plugin is
// loaded while demos are already being recorded
if (auto_recording) *demonum = auto_demonum;
}
orig_SetSignonState(this, state);
}
static void hook_stop_callback(const struct con_cmdargs *args) {
auto_recording = false;
orig_stop_callback(args);
}
// This finds the "demorecorder" global variable (the engine-wide CDemoRecorder
// instance).
static inline void *find_demorecorder(struct con_cmd *cmd_stop) {
// The "stop" command calls the virtual function demorecorder.IsRecording(),
// so just look for the load of the "this" pointer
struct ud udis;
ud_init(&udis);
ud_set_mode(&udis, 32);
ud_set_input_buffer(&udis, (uchar *)con_getcmdcb(cmd_stop), 32);
while (ud_disassemble(&udis)) {
#ifdef _WIN32
if (ud_insn_mnemonic(&udis) == UD_Imov) {
const struct ud_operand *dest = ud_insn_opr(&udis, 0);
const struct ud_operand *src = ud_insn_opr(&udis, 1);
// looking for a mov from an address into ECX, as per thiscall
if (dest->type == UD_OP_REG && dest->base == UD_R_ECX &&
src->type == UD_OP_MEM) {
return *(void **)src->lval.udword;
}
}
#else
#error TODO(linux): implement linux equivalent (cdecl!)
#endif
}
return 0;
}
// This finds "m_bRecording" and "m_nDemoNumber" using the pointer to the
// original "StopRecording" demorecorder function
static inline bool find_recmembers(void *stop_recording_func, void *demorec) {
struct ud udis;
ud_init(&udis);
ud_set_mode(&udis, 32);
// TODO(opt): consider the below: is it really needed? does it matter?
// way overshooting the size of the function in bytes to make sure it
// accomodates for possible differences in different games. we make sure
// to stop early if we find a RET so should be fine
ud_set_input_buffer(&udis, (uchar *)stop_recording_func, 200);
while (ud_disassemble(&udis)) {
#ifdef _WIN32
enum ud_mnemonic_code code = ud_insn_mnemonic(&udis);
if (code == UD_Imov) {
const struct ud_operand *dest = ud_insn_opr(&udis, 0);
const struct ud_operand *src = ud_insn_opr(&udis, 1);
// m_nDemoNumber and m_bRecording are both set to 0
// looking for movs with immediates equal to 0
// the byte immediate refers to m_bRecording
if (src->type == UD_OP_IMM && src->lval.ubyte == 0) {
if (src->size == 8) {
recording = (bool *)mem_offset(demorec, dest->lval.udword);
}
else {
demonum = (int *)mem_offset(demorec, dest->lval.udword);
}
if (recording && demonum) return true; // blegh
}
}
else if (code == UD_Iret) {
return false;
}
#else // linux is probably different here idk
#error TODO(linux): implement linux equivalent
#endif
}
return false;
}
bool demorec_init(void) {
if (!gamedata_has_vtidx_SetSignonState ||
!gamedata_has_vtidx_StopRecording) {
con_warn("demorec: missing gamedata entries for this engine\n");
return false;
}
cmd_stop = con_findcmd("stop");
if (!cmd_stop) { // can *this* even happen? I hope not!
con_warn("demorec: couldn't find \"stop\" command\n");
return false;
}
demorecorder = find_demorecorder(cmd_stop);
if (!demorecorder) {
con_warn("demorec: couldn't find demo recorder instance\n");
return false;
}
void **vtable = *(void ***)demorecorder;
// XXX: 16 is totally arbitrary here! figure out proper bounds later
if (!os_mprot(vtable, 16 * sizeof(void *), PAGE_EXECUTE_READWRITE)) {
#ifdef _WIN32
char err[128];
OS_WINDOWS_ERROR(err);
#else
const char *err = strerror(errno);
#endif
con_warn("demorec: couldn't unprotect CDemoRecorder vtable: %s\n", err);
return false;
}
if (!find_recmembers(vtable[7], demorecorder)) {
con_warn("demorec: couldn't find m_bRecording and m_nDemoNumber\n");
return false;
}
orig_SetSignonState = (f_SetSignonState)hook_vtable(vtable,
gamedata_vtidx_SetSignonState, (void *)&hook_SetSignonState);
orig_StopRecording = (f_StopRecording)hook_vtable(vtable,
gamedata_vtidx_StopRecording, (void *)&hook_StopRecording);
orig_stop_callback = cmd_stop->cb;
cmd_stop->cb = &hook_stop_callback;
sst_autorecord->base.flags &= ~CON_HIDDEN;
return true;
}
void demorec_end(void) {
void **vtable = *(void ***)demorecorder;
unhook_vtable(vtable, gamedata_vtidx_SetSignonState,
(void *)orig_SetSignonState);
unhook_vtable(vtable, gamedata_vtidx_StopRecording,
(void *)orig_StopRecording);
cmd_stop->cb = orig_stop_callback;
}
// vi: sw=4 ts=4 noet tw=80 cc=80
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