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/*
* Copyright © Hayden K <imaciidz@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 "con_.h"
#include "errmsg.h"
#include "feature.h"
#include "intdefs.h"
#include "langext.h"
#include "os.h"
#include "x86.h"
#include "x86util.h"
FEATURE("chat rate limit removal")
GAMESPECIFIC(L4Dbased) // Tested/known to work in L4D1/2, L4D:S, and Portal 2.
static uchar *patchedbyte;
// Same method as SAR here. Basically, the game only lets you chat every 0.66s.
// So, instead of adding 0.66 to the current time, we subtract it, and that
// means we can always chat immediately.
static inline bool find_ratelimit_insn(struct con_cmd *cmd_say) {
// Find the add instruction
uchar *insns = (uchar *)cmd_say->cb;
for (uchar *p = insns; p - insns < 128;) {
// find FADD
if (p[0] == X86_FLTBLK5 && p[1] == X86_MODRM(0, 0, 5)) {
patchedbyte = p + 1;
return true;
}
// Portal 2, L4D2 2125-2134, L4D:S all use SSE2, so try finding ADDSD
if (p[0] == X86_PFX_REPN && p[1] == X86_2BYTE & p[2] == X86_2B_ADD) {
patchedbyte = p + 2;
return true;
}
NEXT_INSN(p, "chat rate limit");
}
return false;
}
static inline bool patch_ratelimit_insn() {
// if FADD replace with FSUB; otherwise it is ADDSD, replace that with SUBSD
if (!os_mprot(patchedbyte, 1, PAGE_EXECUTE_READWRITE)) {
errmsg_errorsys("failed to patch chat rate limit: "
"couldn't make memory writable");
return false;
}
if (*patchedbyte == X86_MODRM(0, 0, 5)) *patchedbyte = X86_MODRM(0, 4, 5);
else *patchedbyte = X86_2B_SUB;
return true;
}
static inline void unpatch_ratelimit_insn() {
// same logic as above but in reverse
if (*patchedbyte == X86_MODRM(0, 4, 5)) *patchedbyte = X86_MODRM(0, 0, 5);
else *patchedbyte = X86_2B_ADD;
}
INIT {
struct con_cmd *cmd_say = con_findcmd("say");
if_cold (!cmd_say) return false;
if (!find_ratelimit_insn(cmd_say)) {
errmsg_errorx("couldn't find chat rate limit instruction");
return FEAT_INCOMPAT;
}
if (!patch_ratelimit_insn()) {
errmsg_errorx("couldn't patch chat rate limit");
return FEAT_FAIL;
}
return FEAT_OK;
}
END {
unpatch_ratelimit_insn();
}
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