5.8 KiB
Piracy Checks
Perfect Dark contains several checks to determine if the game is running in unusual conditions, such as with a modified boot loader or with modified functions. The functions which check for these are in various places throughout the code and some even occur during gameplay. Many of these functions are themselves checked by other functions. In other words, the game detects if you've defeated the first measure then applies a second measure.
If piracy is detected, the game will either corrupt certain functions in memory which causes instability and crashes, or it will alter things within the game to annoy you.
The decomp project wraps all decompiled piracy checks in #if PIRACYCHECKS statements. The project is built by default with piracy checks enabled. These are generally fine to keep enabled even when making changes to the source because the project recalculates and updates the expected checksums during the build process.
List of Piracy Checks
bootPhase1
When Called: On power-on before the legal screen appears.
What It Checks: Checks an address in the bootloader (ROM address 0x2e8) for a known value.
Payload: Goes into an infinite loop so the system never boots.
__scHandleTasks
When Called: On every frame.
What It Checks: Checksums bootPhase1 to make sure it hasn't been modified.
Payload: Writes 40 bytes of 0xff to 0x80095210. This appears to be related to sound effects but has no obvious effect.
cheatMenuHandleDialog
When Called: When the Cheats menu dialog is opened.
What It Checks: Checksums __scHandleTasks to make sure it hasn't been modified.
Payload: Corrupts __scHandleTasks by nopping the call to __scAppendList and some of the function arguments to osRecvMesg. Most likely results in a crash.
func0f08e2ac
When Called: Unsure. Related to doors.
What It Checks: Checks that the value of osCicId is 6105.
Payload: Rewrites the start of func0f08f968 so it immediately returns false. This makes it impossible to open doors.
propobjHandlePickupByAibot
When Called: When a simulant in multiplayer picks up an item.
What It Checks: Checksums func0f08e2ac to make sure it hasn't been modified.
Payload: Rewrites the start of func0f03978c so it immediately returns true. This makes all guards able to see Jo through walls.
chrUncloak
When Called: When a guard uncloaks.
What It Checks: Checksums propobjHandlePickupByAibot to make sure it hasn't been modified.
Payload: Disables the ability for the player and other characters to go up or down slopes. This is done by nopping the jr ra instruction in cdFindGroundY, which causes it to flow into the following function, which unconditionally returns false and only exists for this purpose.
chrsCheckForNoise
When Called: When a guard hears you.
What It Checks: Checksums __scHandleRetrace to make sure it hasn't been modified. That function doesn't appear to have any piracy checks, however.
Payload: Sets the Skedar King's body file number to zero, which causes the game to crash when loading Skedar Ruins or WAR.
lvGetSlowMotionType
When Called: On each tick when unpaused.
What It Checks: Checks an address in the bootloader (ROM address 0xa5c) for a known value.
Payload: Corrupts the rspboot microcode, causing a crash.
lvInit
When Called: When loading any stage (including title screen).
What It Checks: Checksums lvGetSlowMotionType to make sure it hasn't been modified.
Payload: Writes 16 bytes of data to the start of EEPROM. Unsure what this does, but it's probably corrupting it.
propAllocateEyespy
When Called: When loading any stage that uses the eyespy.
What It Checks: Checksums lvInit to make sure it hasn't been modified.
Payload: Nops func00012914 entirely. Unsure what effect this has. This means any time that function is called it'll flow into the following function, which just returns.
bgInit
When Called: When loading a normal stage (eg. CI Training).
What It Checks: Checks an address in the bootloader (ROM address 0x454) for a known value.
Payload: Copies 64 bytes from a random location in ROM to a random location in RAM.
chrConsiderGrenadeThrow
When Called: When a chr decides to throw a grenade.
What It Checks: Checksums bgInit to make sure it hasn't been modified.
Payload: Surrounds the player in infinite explosions.
tagsAllocatePtrs
When Called: When loading a normal stage (eg. CI Training).
What It Checks: Calls mtxGetObfuscatedRomBase to get the value of osRomBase then compares it with a known value.
Payload: Copies 4KB from a random location in ROM to a random location in RAM.
bgun0f09e144
When Called: Unknown.
What It Checks: Checksums tagsAllocatePtrs to make sure it hasn't been modified.
Payload: Corrupts tagsAllocatePtrs by writing 28 bytes of 0xff.
func0f0069dc
When Called: Unknown.
What It Checks: Checksums func00015fd0 to make sure it hasn't been modified.
Payload: Corrupts bgInit by writing 16 bytes of 0x12 to a random address within that function.
func0f15c920
When Called: Unknown.
What It Checks: Checksums func0f0069dc to make sure it hasn't been modified.
Payload: Corrupts bgBuildTables by adding a fixed amount to 16 bytes within that function.
glassDestroy
When Called: When the player breaks glass.
What It Checks: Checks an address in the bootloader (ROM address 0xdc0) for a known value.
Payload: Sets the audio frequency to a high value which makes everyone sound like chipmunks.
explosionAlertChrs
When Called: When there's an explosion.
What It Checks: Checksums glassDestroy to make sure it hasn't been modified.
Payload: Makes all explosions huge.