IPC (SDK)

IPC is the SDK library that provides functions for communication with IOS. It seems to also mirror some IOS syscalls, suggesting that IOS was originally planned to run on the Broadway.

Memory allocation

Memory used by IPC and NAND is mainly allocated with iosAllocAligned, which allocates from one of 8 heaps, each with the following structure:

struct HeapBlockHeader {
	u16 magic;                    // always 0xbabe
	u16 status;                   // 0 means free, 1 means it is in the process of being allocated, 2 means it is being used
	u32 size;
	struct HeapBlockHeader *prev; // points to the same heap block if it is allocated, NULL for the beginning of the heap
	struct HeapBlockHeader *next; // NULL for the end of the heap or if this heap block is allocated
}

struct Heap {
	void *base;
	u32 processId; // See note below
	u32 size;
	struct HeapBlockHeader *firstBlock;
}

processId is probably only present to match the struct used by IOS; it is never set or checked by IPC, but it may be used by IOS's memory management.