Nintendo Switch Brew

Switch 2: Compatibility Mode: Difference between revisions

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These binaries are compiled with PAC enabled.
These binaries are compiled with PAC enabled.


= NPDM Adjustments =
* Game has access to SVC 0x54, 0x80 even though it's not in the game NPDM.
* Game has CoreMask 0x3F (so access to core0-5) even though the game NPDM only has CoreMask 0x7.
* It's unknown if the service whitelist is updated for the game when running in Compatibility mode.


= Hooking =
= Hooking =
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Below is a breakdown what some of the hooks and what their purpose is.
Below is a breakdown what some of the hooks and what their purpose is.
== Modules ==
Rtld is identical besides the extra page at the end of .bss for [[#CompatibilityParameter|CompatibilityParameter]].
The compat modules are loaded between the main module and the (sub)sdk* modules.
The existing modules are not directly modified.


== CompatibilityParameter ==
== CompatibilityParameter ==
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To retrieve this pointer, [[#nnCompatThin|nnCompatThin]] intercepts the nnosInitialize function and retrieves it from there. Normally, a game doesn't use the ProgramParameter so it doesn't care this parameter was passed.
To retrieve this pointer, [[#nnCompatThin|nnCompatThin]] intercepts the nnosInitialize function and retrieves it from there. Normally, a game doesn't use the ProgramParameter so it doesn't care this parameter was passed.
{| class=wikitable
! Offset || Type || Name
|-
| 0x00 || ModuleSdkInfo[11] || Modules
|-
| 0xB0 || u64 || ModulesCount
|-
| 0xB8 || u64 || GraphicsControlData
|-
| 0xC0 || u64 || MovieControlData
|-
| 0xC8 || u64 || AudioControlData
|-
| 0xD0 || u64 || [[#MiscControlData]]
|}
=== MiscControlData ===
{| class=wikitable
! Bit || Name || Description
|-
| 0 || PreventShaderCacheOpenFile || Prevents game from opening file: "ROM:/data/scaleform_cache/GFxShaders.cache".
|-
| 1 || PreventShaderCacheGetEntryType || Prevents game from getting the entry type on 5 different hardcoded paths.
|-
| 2 || PreventShaderCacheOpenDirectory || Prevents game from opening directory: "host:/shaders/build/"
|-
| 4 || SerializeSavedataAccess || A global mutex is taken when a file starting with "savedata" is opened, and held until the file has been closed. Commit-action also takes the mutex, so the commit will not complete until the file has been closed.
|-
| 6 || PreventNegativeVibrationValue ||
|-
| 10 || NeedsWaitingLaunchLogo ||
|-
| 13 || ExtraSleepForOfflineWebApplet ||
|-
|}
=== ModuleSdkInfo ===
{| class=wikitable
! Offset || Type || Name
|-
| 0x00 || const char* || SdkNameStringPtr. Points to a string of the form "SDK MW+Nintendo+NintendoSdk_nnSdk-XX_Y_Z-Release".
|-
| 0x08 || u32 || SdkNameStringLength
|-
|}
= ApplicationCompatibilityInfo =
The [[Switch 2: Title list|ApplicationCompatibilityInfo]] SystemData contains "ApplicationCompatibilityInfo.json".
The json "records" contains an array, each object entry then contains the following:
* "application_id": "0x<lowercase hex ApplicationId>"
* "target_max_version": <value> (normally u32-max)
* "application_layer_info": This object contains various number fields, only fields needed by the current entry are present. "graphics_config", "misc_config", ...
** The data from here is likely passed as input to [[#CompatibilityParameter|CompatibilityParameter]].


= nnCompatTrampoline =
= nnCompatTrampoline =
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{| class=wikitable
{| class=wikitable
! Hooked Symbol || Difference
! Hooked Symbol || Difference || Conditional
|-
| nnosInitialize || Captures the ProgramArgument parameter where the [[#CompatibilityParameter]] is stored. ||
|-
| nn::os::CreateThread || No change. ||
|-
| nn::os::SetThreadCoreMask || No change. ||
|-
| nn::os::GetThreadAvailableCoreMask, nn::os::GetThreadAvailableCoreMask || Returns actual core mask masked with 0x7, effectively pretending that there are only 3 CPU cores available. ||
|-
| nn::audio::GetAudioInName || If the primary audio in name is "XUac", it returns the secondary device name instead. Presumably, the "XUac" device has been removed in Switch 2. ||
|-
| nn::audio::GetReleasedWaveBuffer || Now returns NULL under certain circumstances. || AudioControlData bit0
|-
| nn::web::OfflineWebSession::Appear || Added sleep 50000000 before calling the original function. || MiscControlData bit13
|-
|-
| nnosInitialize || Captures the ProgramArgument parameter where the [[#CompatibilityParameter]] is stored.
| nn::ssl::Connection::SetSocketDescriptor || Calls nn::socket::Fnctl(..., 3); nn::socket::Fnctl(..., 4); on the socket fd. || MiscControlData bit15
|-
|-
| nn::os::CreateThread || No change.
| nn::swkbd::InlineKeyboard::GetImage, nn::swkbd::InlineKeyboard::Calc || Takes a shared mutex before calling original functions. No other changes. Probably prevents a race condition that only manifests on Switch 2. ||
|-
|-
| nn::os::SetThreadCoreMask || No change.
| nn::socket::Socket || If nn::socket::IsInitialized() is 0, sleep for 1 second, and see it reaches 1 before calling the original function. Probably prevents a race condition that only manifests on Switch 2. || MiscControlData bit9
|-
|-
| nn::os::GetThreadAvailableCoreMask || Returns actual core mask masked with 0x7, effectively pretending that there are only 3 CPU cores available.
| nn::os::TimedAcquireSemaphore || Force arg1=true. || MiscControlData bit8.
|-
|-
| nn::audio::GetAudioInName || If the primary audio in name is "XUac", it returns the secondary device name instead. Presumably, the "XUac" device has been removed in Switch 2.
| nn::os::QueryMemoryInfo,nn::os::QueryMemoryInfoForDebug || Hides stolen Heap memory that it uses for itself... ||
|-
|-
| nn::audio::GetReleasedWaveBuffer || Now returns NULL under certain circumstances.
| nn::hid::VibrationPlayer::SetCurrentPosition || If position is negative, drop the call. || MiscControlData bit6
|}
|}


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|-
|-
| nn::os::ConvertToTick || Uses conversion ratio 31250000 instead of 19200000.
| nn::os::ConvertToTick || Uses conversion ratio 31250000 instead of 19200000.
|-
| gl*, _gl*, egl* || OpenGL API translation for new GPU?
|-
| vk* || Vulkan API translation for new GPU?
|-
| NvOsFopen ||
|-
| NvOsGetTimeMS || Adjusted for new clock frequency.
|-
| nn::vi::* || Translation layer because vi:u was removed?
|-
| nn::pl::IsRunningOnOunce || Returns 1 instead of 0.
|}
|}
Retrieved from "https://switchbrew.org/wiki/Switch_2:_Compatibility_Mode"