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Patches for Resident Evil 2/3 audio issues

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These games are erroneously zeroing buffers before they can be fully copied to ARAM by DMA. The responsible memset() calls are followed by a call to DVDRead() which issues dcbi instructions that effectively cancel the memset() on real hardware. Because Dolphin lacks dcache emulation, the effects of the memset() calls are observed, which causes missing audio.

In a comment on the original bug, phire noted that the issue can be corrected by simply nop'ing out the offending memset() calls. Because the games dynamically load different .rel executables based on the character and/or language, the addresses of these calls can vary.

To deal generally with the problem of code being dynamically loaded to fixed, known addresses, the patch engine is extended to support conditional patches which require a match against a known value. This sort of thing is already achievable with Action Replay/Gecko codes, but their use depends on enabling cheats globally in Dolphin, which is not a prerequisite shared by patches.

Patches are included for every region, character, and language combination. They are enabled by default.

The end result is an approximation of the games' behavior on real hardware without the associated complexity of proper dcache emulation.

https://bugs.dolphin-emu.org/issues/9840
This commit is contained in:
smurf3tte
2020-12-29 14:24:46 -08:00
parent 2615da820d
commit f3b8a985e7
10 changed files with 196 additions and 44 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
Source/Core/Core/PatchEngine.cpp
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@ -90,6 +90,11 @@ void LoadPatchSection(const std::string& section, std::vector<Patch>& patches, I
bool success = true;
success &= TryParse(items[0], &pE.address);
success &= TryParse(items[2], &pE.value);
if (items.size() >= 4)
{
success &= TryParse(items[3], &pE.comparand);
pE.conditional = true;
}
const auto iter =
std::find(s_patch_type_strings.begin(), s_patch_type_strings.end(), items[1]);
@ -184,16 +189,20 @@ static void ApplyPatches(const std::vector<Patch>& patches)
{
u32 addr = entry.address;
u32 value = entry.value;
u32 comparand = entry.comparand;
switch (entry.type)
{
case PatchType::Patch8Bit:
PowerPC::HostWrite_U8(static_cast<u8>(value), addr);
if (!entry.conditional || PowerPC::HostRead_U8(addr) == static_cast<u8>(comparand))
PowerPC::HostWrite_U8(static_cast<u8>(value), addr);
break;
case PatchType::Patch16Bit:
PowerPC::HostWrite_U16(static_cast<u16>(value), addr);
if (!entry.conditional || PowerPC::HostRead_U16(addr) == static_cast<u16>(comparand))
PowerPC::HostWrite_U16(static_cast<u16>(value), addr);
break;
case PatchType::Patch32Bit:
PowerPC::HostWrite_U32(value, addr);
if (!entry.conditional || PowerPC::HostRead_U32(addr) == comparand)
PowerPC::HostWrite_U32(value, addr);
break;
default:
// unknown patchtype