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Make it as bright as BedrockTools' Fullbright #1

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63 changes: 49 additions & 14 deletions src/main.cpp
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Original file line number Diff line number Diff line change
@@ -1,38 +1,73 @@
#include <cstdint>
#include <cstring>
#include <cstddef>
#include <sys/mman.h>
#include <unistd.h>

#include "pl/Gloss.h"
#include "pl/Signature.h"

static const char* GFX_GAMMA_SIGNATURE = "? ? ? 52 ? ? ? 2F ? ? ? 1E ? ? ? 72 ? ? ? 1E ? ? ? D1 03 01 27 1E ? ? ? D1 E0 03 15 AA ? ? ? 52 ? ? ? 52";
static const char* GFX_GAMMA_SIGNATURE =
"? ? ? 52 ? ? ? 2F ? ? ? 1E ? ? ? 72 ? ? ? 1E ? ? ? D1 "
"03 01 27 1E ? ? ? D1 E0 03 15 AA ? ? ? 52 ? ? ? 52";

constexpr uint32_t FULLBRIGHT_GAMMA = 100;

static constexpr uint32_t MakeMovW8(uint32_t imm) {
return 0x52800000u | ((imm & 0xFFFFu) << 5) | 8u;
}

constexpr uint32_t MOV_W8_10 = 0x52800148;
constexpr uint32_t MOV_W8_FULLBRIGHT = MakeMovW8(FULLBRIGHT_GAMMA);
constexpr uint32_t SCVTF_S2_W8 = 0x1E220102;
constexpr uint32_t EXPECTED_FMOV_S2_1 = 0x1E2E1002;
constexpr ptrdiff_t OFFSET_GAMMA_CONST = 12;
constexpr ptrdiff_t OFFSET_FMOV = 16;

constexpr ptrdiff_t OFFSET_MOVK = 12;
constexpr ptrdiff_t OFFSET_FMOV = 16;
static bool ReadInsn(uintptr_t addr, uint32_t& out) {
std::memcpy(&out, reinterpret_cast<void*>(addr), sizeof(out));
return true;
}

static bool PatchMemory(void* addr, uint32_t insn) {
uintptr_t page_start = (uintptr_t)addr & ~(uintptr_t)4095;
size_t page_size = (sizeof(insn) + 4095) & ~(size_t)4095;
if (mprotect((void*)page_start, page_size, PROT_READ | PROT_WRITE | PROT_EXEC) != 0)
uintptr_t p = reinterpret_cast<uintptr_t>(addr);

long page_size_long = sysconf(_SC_PAGESIZE);
uintptr_t page_size = page_size_long > 0 ? static_cast<uintptr_t>(page_size_long) : 4096;

uintptr_t page_start = p & ~(page_size - 1);
uintptr_t page_end = (p + sizeof(insn) + page_size - 1) & ~(page_size - 1);
size_t len = page_end - page_start;

if (mprotect(reinterpret_cast<void*>(page_start), len, PROT_READ | PROT_WRITE | PROT_EXEC) != 0)
return false;
memcpy(addr, &insn, sizeof(insn));
__builtin___clear_cache((char*)addr, (char*)addr + sizeof(insn));
mprotect((void*)page_start, page_size, PROT_READ | PROT_EXEC);

std::memcpy(addr, &insn, sizeof(insn));
__builtin___clear_cache(reinterpret_cast<char*>(addr),
reinterpret_cast<char*>(addr) + sizeof(insn));

mprotect(reinterpret_cast<void*>(page_start), len, PROT_READ | PROT_EXEC);
return true;
}

static bool PatchGfxGamma() {
uintptr_t base = pl::signature::pl_resolve_signature(GFX_GAMMA_SIGNATURE, "libminecraftpe.so");
uintptr_t base = pl::signature::pl_resolve_signature(
GFX_GAMMA_SIGNATURE,
"libminecraftpe.so"
);

if (base == 0)
return false;

if (*reinterpret_cast<uint32_t*>(base + OFFSET_FMOV) != 0x1E2E1002)
uint32_t old_fmov = 0;
ReadInsn(base + OFFSET_FMOV, old_fmov);

if (old_fmov != EXPECTED_FMOV_S2_1)
return false;

return PatchMemory(reinterpret_cast<void*>(base + OFFSET_MOVK), MOV_W8_10)
&& PatchMemory(reinterpret_cast<void*>(base + OFFSET_FMOV), SCVTF_S2_W8);
bool ok1 = PatchMemory(reinterpret_cast<void*>(base + OFFSET_GAMMA_CONST), MOV_W8_FULLBRIGHT);
bool ok2 = PatchMemory(reinterpret_cast<void*>(base + OFFSET_FMOV), SCVTF_S2_W8);

return ok1 && ok2;
}

__attribute__((constructor))
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