Thread Local Storage
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Each thread is given a 0x200-byte thread-local-storage block by the kernel. It is used during IPC communications. Each KProcess has a linked list of KThreadLocalPage objects and each object has a pointer to a page(0x1000 bytes) of FCRAM, which is used for up to 8 thread-local-storage blocks. The KThreadLocalPage is used to track which thread-local-storage blocks are used so it can allocate new ones as new threads are created.
A pointer to the thread-local-storage can be read using the ARM instruction:
mrc 15, 0, rX, cr13, cr0, 3
Every application has RW access to its thread-local-storage.
The kernel requires the application to put IPC parameters and IPC static buffers inside the thread-local-storage:
| Offset | Size | Description |
|---|---|---|
| 0x00 | 0x40 | Undefined, can be used by application for any purpose |
| 0x40 | 0x44 | Exception handler return address |
| 0x44 | 0x48 | Exception handler SP control (1 = use aligned SP, other = use arbitrary memory, must be mapped & RW) |
| 0x48 | 0x4C | Exception handler context control (0 = use SP control memory, 1 = use aligned SP, other = use arbitrary memory, must be mapped & RW) |
| 0x4C | 0x80 | Undefined |
| 0x80 | 0x100 | IPC command with parameters |
| 0x180 | 0x80 | IPC static buffers: 16 pairs of a static buffer translation descriptor (specifying the buffer size) and a buffer pointer |