diff options
Diffstat (limited to 'src/demorec.c')
| -rw-r--r-- | src/demorec.c | 112 |
1 files changed, 44 insertions, 68 deletions
diff --git a/src/demorec.c b/src/demorec.c index bcc7367..a384e55 100644 --- a/src/demorec.c +++ b/src/demorec.c @@ -1,6 +1,6 @@ /* * Copyright © 2021 Willian Henrique <wsimanbrazil@yahoo.com.br> - * Copyright © 2021 Michael Smith <mikesmiffy128@gmail.com> + * Copyright © 2022 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 @@ -27,8 +27,9 @@ #include "intdefs.h" #include "mem.h" #include "os.h" -#include "udis86.h" +#include "ppmagic.h" #include "vcall.h" +#include "x86.h" #define SIGNONSTATE_SPAWN 5 // ready to receive entity packets #define SIGNONSTATE_FULL 6 // fully connected, first non-delta packet received @@ -95,7 +96,6 @@ static void hook_stop_callback(const struct con_cmdargs *args) { orig_stop_callback(args); } - // The engine allows usermessages up to 255 bytes, we add 2 bytes of overhead, // and then there's the leading bits before that too (see create_message) static char bb_buf[DEMOREC_CUSTOM_MSG_MAX + 4]; @@ -139,75 +139,59 @@ void demorec_writecustom(void *buf, int len) { bitbuf_reset(&bb); } +// XXX: probably want some general foreach-instruction macro once we start doing +// this kind of hackery in multiple different places +#define NEXT_INSN(p) do { \ + int _len = x86_len(p); \ + if (_len == -1) { \ + con_warn("demorec: %s: unknown or invalid instruction\n", __func__); \ + return false; \ + } \ + (p) += _len; \ +} while (0) // 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)) { +static inline bool find_demorecorder(struct con_cmd *cmd_stop) { #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; - } + uchar *stopcb = (uchar *)con_getcmdcb(cmd_stop); + // The "stop" command calls the virtual function demorecorder.IsRecording(), + // so just look for the load of the "this" pointer into ECX + for (uchar *p = stopcb; p - stopcb < 32;) { + if (p[0] == X86_MOVRMW && p[1] == X86_MODRM(0, 1, 5)) { + void **indirect = mem_loadptr(p + 2); + demorecorder = *indirect; + return true; } + NEXT_INSN(p); + } #else #warning TODO(linux): implement linux equivalent (cdecl!) - return 0; #endif - } - return 0; + return false; } // 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) { - 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)) { +static inline bool find_recmembers(void *stoprecording) { #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(demorecorder, - dest->lval.udword); - } - else { - demonum = (int *)mem_offset(demorecorder, - dest->lval.udword); - } - if (recording && demonum) return true; // blegh - } + for (uchar *p = (uchar *)stoprecording; p - (uchar *)stoprecording < 128;) { + // m_nDemoNumber = 0 -> mov dword ptr [<reg> + off], 0 + // XXX: might end up wanting constants for the MRM field masks? + if (p[0] == X86_MOVMIW && (p[1] & 0xC0) == 0x80 && + mem_load32(p + 6) == 0) { + demonum = mem_offset(demorecorder, mem_load32(p + 2)); } - else if (code == UD_Iret) { - return false; + // m_bRecording = false -> mov byte ptr [<reg> + off], 0 + else if (p[0] == X86_MOVMI8 && (p[1] & 0xC0) == 0x80 && p[6] == 0) { + recording = mem_offset(demorecorder, mem_load32(p + 2)); } + if (recording && demonum) return true; // blegh + NEXT_INSN(p); + } #else // linux is probably different here idk -#warning TODO(linux): implement linux equivalent - return false; +#warning TODO(linux): implement linux equivalent (???) #endif - } return false; } @@ -215,6 +199,7 @@ static inline bool find_recmembers(void *stop_recording_func) { // network packet, wraps it up in the appropriate demo framing format and writes // it out to the demo file being recorded. static bool find_WriteMessages(void) { + // TODO(compat): probably rewrite this to just scan for a call instruction! const uchar *insns = (*(uchar ***)demorecorder)[gamedata_vtidx_RecordPacket]; // RecordPacket calls WriteMessages pretty much right away: // 56 push esi @@ -228,10 +213,10 @@ static bool find_WriteMessages(void) { // So we just double check the byte pattern... static const uchar bytes[] = #ifdef _WIN32 -{0x56, 0x57, 0x8B, 0xF1, 0x8D, 0xBE, 0x8C, 0x06, 0x00, 0x00, 0x57, 0xE8}; + HEXBYTES(56, 57, 8B, F1, 8D, BE, 8C, 06, 00, 00, 57, E8); #else #warning This is possibly different on Linux too, have a look! -{-1, -1, -1, -1, -1, -1}; + {-1, -1, -1, -1, -1, -1}; #endif if (!memcmp(insns, bytes, sizeof(bytes))) { ssize off = mem_loadoffset(insns + sizeof(bytes)); @@ -249,21 +234,17 @@ bool demorec_init(void) { 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) { + if (!find_demorecorder(cmd_stop)) { 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 @@ -276,7 +257,7 @@ bool demorec_init(void) { return false; } - if (!find_recmembers(vtable[7])) { + if (!find_recmembers(vtable[7])) { // XXX: stop hardcoding this!? con_warn("demorec: couldn't find m_bRecording and m_nDemoNumber\n"); return false; } @@ -301,11 +282,6 @@ bool demorec_custom_init(void) { con_warn("demorec: custom: missing gamedata entries for this engine\n"); return false; } - // TODO(featgen): auto-check this factory - if (!factory_engine) { - con_warn("demorec: missing required interfaces\n"); - return false; - } // More UncraftedkNowledge: // > yeah okay so [the usermessage length is] 11 bits if the demo protocol |