In memory of Ben “bushing” Byer, who passed away on Monday, February 8th, 2016.

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10,838 bytes added ,  21:58, 11 September 2015
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== Syscalls (via undefined instructions) ==
 
== Syscalls (via undefined instructions) ==
 +
Similarly to the Wii's IOS, the IOSU uses a syscall table that is stored toward the end of the kernel area inside the main ARM binary (fw.img).
   −
Syscalls are invoked by way of the invalid instruction handler; syscalls take the form 0xE7F000F0 | (syscall_num << 8). (E.g. E7F000F0 is syscall 0, E7F036F0 is syscall 0x36, etc.). IOS has 0x82 available syscalls.
+
The second vector is the invalid instruction handler, which is used to implement syscalls:
 +
fw:FFFF0000              LDR    PC, =_reset
 +
fw:FFFF0004              LDR    PC, =starbuck_syscall_handler
   −
(please feel free to contribute your own findings!)
+
The Starbuck syscall handler:
 +
starbuck_syscall_handler
 +
    STMFA          SP, {R0-LR}^
 +
    MRS            R8, SPSR
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    STR            R8, [SP]
 +
    STR            LR, [SP,#0x40]
 +
    LDR            R10, [LR,#-4]  ; R10 = E7F0XXXX  (the invalid instruction)
 +
    BIC            R9, R10, #0xFF00
 +
    LDR            R8, =0xE7F000F0  ; Syscall base
 +
    CMP            R9, R8            ; Were any bits set other than the syscall number
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    BNE            invalid_syscall
 +
    MOV            R10, R10,ASR#8
 +
    AND            R10, R10, #0xFF
 +
    CMP            R10, #0x94        ; Max index of syscall (can possibly vary)
 +
    BGT            return_to_caller
 +
    MOV            R8, SP
 +
    MOV            R11, #0x1F
 +
    MSR            CPSR_c, R11      ; Switch to system mode and disable FIQ/IRQ
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    LDR            R8, [R8,#0x44]
 +
    LDR            R11, =syscall_stack_arg_counts
 +
    LDR            R11, [R11,R10,LSL#2]  ; Number of args on stack for this syscall
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    ADD            SP, SP, R11,LSL#2
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get_stack_arg                           
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    CMP            R11, #0
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    BEQ            find_syscall_and_jump
 +
    LDR            R9, [SP,#-4]! ; Copy argument value
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    STR            R9, [R8,#-4]!
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    SUB            R11, R11, #1
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    B              get_stack_arg
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find_syscall_and_jump
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    MOV            SP, R8
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    LDR            R11, =syscall_table
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    LDR            R11, [R11,R10,LSL#2]
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    MOV            LR, PC
 +
    BX              R11
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return_to_caller
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    MOV            R11, #0xDB  ; Switch to undefined mode and re-enable FIQ/IRQ
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    MSR            CPSR_c, R11
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    LDR            R11, [SP]
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    MSR            SPSR_cxsf, R11
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    MOV            LR, R0
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    LDMED          SP, {R0-LR}^
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    NOP
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    MOV            R0, LR
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    LDR            LR, [SP,#0x40]
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    MOVS            PC, LR       ; Return
 +
invalid_syscall
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    LDR            SP, =current_thread_ctx_addr
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    LDR            SP, [SP]
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    STR            LR, [SP,#0x40]
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    ADD            SP, SP, #0x40
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    STMFD          SP, {R0-LR}^
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    SUB            R0, SP, #0x40
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    MOV            LR, #6 ; STATE_FAULTED
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    STR            LR, [R0,#0x50]
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    LDR            SP, =debug_args_addr
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    BL              debug_print  ; Illegal Instruction:tid=%d,pid=%d,pc=0x%08x,sp=0x%08x
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    B              schedule_yield
 +
 
 +
Syscalls are invoked by way of the invalid instruction handler; syscalls take the form 0xE7F000F0 | (syscall_num << 8). (E.g. E7F000F0 is syscall 0, E7F036F0 is syscall 0x36, etc.).<br>
 +
The IOSU currently has 0x94 available syscalls (the number of installed syscalls can vary between system versions).<br><br>
 +
NOTE: Official syscall names begin with "IOS_", the rest are merely educated guesses.
    
{|border=1
 
{|border=1
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! ID # !! Internal name !! Description !! Return value
 
! ID # !! Internal name !! Description !! Return value
 
|-
 
|-
C || int IOS_CreateMessageQueue(u32 *ptr, u32 n_msgs) || Create a queue at ptr, for n_msgs messages || The queue ID
+
| 0x00 || int IOS_CreateThread(u32 (*proc)(void* arg), void* arg, u32* stack_top, u32 stacksize, int priority, BOOL detached) || Creates a thread (in paused state) || New threadid or error (negative value)
 +
|-
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| 0x01 || int thread_join(int threadid, u32 *returned_value) || Waits for a thread to finish executing || 0 on success
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|-
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| 0x02 || int thread_cancel(int threadid, u32 unk)  || Cancels an active thread || 0 on success
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|-
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| 0x03 || int get_tid() || Get the current thread's ID || Current threadid
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|-
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| 0x04 || || ||
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|-
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| 0x05 || int get_pid() || Get the current process' ID || Current processid
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|-
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| 0x06 || int get_process_name(int pid, char *out_buffer, u32 out_size) || Get the specified process' name string || 0 on success
 +
|-
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| 0x07 || int thread_resume(int threadid) || Resume the specified thread || 0 on success
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|-
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| 0x08 || int thread_suspend(int threadid) || Suspend the specified thread || 0 on success
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|-
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| 0x09 || int thread_yield() || Yield execution to any higher priority threads || 0 on success
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|-
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| 0x0A || int IOS_GetThreadPriority(int threadid) || Get the priority of the specified thread || The thread's priority or error (negative value)
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|-
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| 0x0B || int IOS_SetThreadPriority(int threadid, int priority) || Set the priority of the specified thread || 0 on success
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|-
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| 0x0C || int IOS_CreateMessageQueue(u32 *ptr, u32 n_msgs) || Create a queue at ptr, for n_msgs messages || The queue ID
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|-
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| 0x0D || int IOS_DestroyMessageQueue(int queueid) || Destroy a message queue || 0 on success
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|-
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| 0x0E || int IOS_SendMessage(int queueid, u32 message, u32 flags) || Add a message to the end queue || 0 on success
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|-
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| 0x0F || int IOS_JamMessage(int queueid, u32 message, u32 flags) || Add a message to the front of a queue || 0 on success
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|-
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| 0x10 || int IOS_ReceiveMessage(int queueid, u32 *message, u32 flags) || Fetch a message from the front of a queue || 0 on success
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|-
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| 0x11 || int IOS_HandleEvent(int device, int queueid, int message) || Register queueid as a handler for interrupts generated by device (sends message to queueid when device's interrupt is triggered) || 0 on success
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|-
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| 0x12 || int unregister_event_handler(int device) || Unregister handler for device || 0 on success
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|-
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| 0x13 || int IOS_CreateTimer(int time_us, int repeat_time_us, int queueid, u32 message) || Create a timer that sends a message to a queue after the elapsed period(s) || Timerid or error (negative value)
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|-
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| 0x14 || int IOS_RestartTimer(int timerid, int time_us, int repeat_time_us) || Restart a timer using the specified period(s) || 0 on success
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|-
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| 0x15 || int IOS_StopTimer(int timerid) || Pauses the specified timer || 0 on success
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|-
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| 0x16 || int IOS_DestroyTimer(int timerid) || Destroys the specified timer || 0 on success
 +
|-
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| 0x17 || || ||
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|-
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| 0x18 || || ||
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|-
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| 0x19 || IOS_GetUpTimeStruct(???) || ||
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|-
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| 0x1A || IOS_GetUpTime64(???) || ||
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|-
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| 0x1B || || ||
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|-
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| 0x1C || IOS_GetAbsTimeCalendar(???) || ||
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|-
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| 0x1D || IOS_GetAbsTime64(???) || ||
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|-
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| 0x1E || IOS_GetAbsTimeStruct(???) || ||
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|-
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| 0x1F || || ||
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|-
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| 0x20 || || ||
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|-
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| 0x21 || int check_jtag() || Get the current status of the JTAG || 0 if JTAG is enabled or -4 if disabled
 +
|-
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| 0x22 || || ||
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|-
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| 0x23 || int heap_create(void *ptr, int size) || Create a new heap at ptr of size bytes || The heapid or error (negative value)
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|-
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| 0x24 || int IOS_CreateLocalProcessHeap(void *ptr, int size) || Create a new local process heap of size bytes || The heap ID or error (negative value)
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|-
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| 0x25 || int IOS_CreateCrossProcessHeap(int size) || Create a new cross process heap of size bytes || The heap ID or error (negative value)
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|-
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| 0x26 || int heap_destroy(int heapid) || Destroy the specified heap || 0 on success
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|-
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| 0x27 || void* IOS_Alloc(int heapid, u32 size) || Allocate size bytes from the specified heap || Pointer to memory
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|-
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| 0x28 || void* heap_alloc_aligned(int heapid, u32 size, u32 align) || Allocate size bytes from the specified heap with the requested alignment || Pointer to aligned memory
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|-
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| 0x29 || void IOS_Free(int heapid, void *ptr)  || Release allocated memory back to the heap || 0 on success
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|-
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| 0x2A || || ||
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|-
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| 0x2B || || ||
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|-
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| 0x2C || || ||
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|-
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| 0x2D || BOOL device_register(const char* device, int queueid) || Registers device to the device tree, so it can be opened (from Starbuck and PPC) || 0 on success
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|-
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| 0x2E || || ||
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|-
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| 0x2F || || ||
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|-
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| 0x30 || || ||
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|-
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| 0x31 || || ||
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|-
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| 0x32 || int query_featureid(int featureid, int out_size, void *out_buffer) || ||
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|-
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| 0x33 || int IOS_Open(const char* device, int mode) || Similar to IOS_Open on PPC, except now internal to the IOSU system || Returns an fd or error (negative)
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|-
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| 0x34 || int IOS_Close(int fd) || Close a previously opened fd || 0 on success
 +
|-
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| 0x35 || int IOS_Read(int fd, void *buf, u32 len) || Read len bytes from fd into buf || The number of bytes read or error
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|-
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| 0x36 || int IOS_Write(int fd, const void *buf, u32 len) || Write len bytes to fd from buf || The number of bytes written or error
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|-
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| 0x37 || int IOS_Seek(int fd, int offset, int origin) || Seek to offset relative to origin || The new absolute offset or error
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|-
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| 0x38 || int IOS_Ioctl(int fd, u32 request, void *input_buffer, u32 input_buffer_len, void *output_buffer, u32 output_buffer_len) || Perform the requested IOCTL || Return value from IOCTL
 +
|-
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| 0x39 || int IOS_Ioctlv(int fd, u32 request, u32 vector_count_in, u32 vector_count_out, struct iovec *vector) || Perform the requested IOCTL || Return value from IOCTL
 +
|-
 +
| 0x3A || int IOS_OpenAsync(const char* device, int mode, int queueid, ipcmessage *message) || Async implementation of IOS_Open || 0 on success, ipcmessage is sent to the queue with the command's return value
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|-
 +
| 0x3B || int IOS_CloseAsync(int fd, int queueid, ipcmessage *message) || Async implementation of IOS_Close || 0 on success
 +
|-
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| 0x3C || int IOS_ReadAsync(int fd, void *buf, u32 len, int queueid, ipcmessage *message) || Async implementation of IOS_Read || 0 on success
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|-
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| 0x3D || int IOS_WriteAsync(int fd, const void *buf, u32 len, int queueid, ipcmessage *message) || Async implementation of IOS_Write || 0 on success
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|-
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| 0x3E || int IOS_SeekAsync(int fd, int offset int origin, int queueid, ipcmessage *message) || Async implementation of IOS_Seek || 0 on success
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|-
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| 0x3F || int IOS_IoctlAsync(int fd, u32 request, void *input_buffer, u32 input_buffer_len, void *output_buffer, u32 output_buffer_len, int queueid, ipcmessage *message) || Async implementation of IOS_Ioctl || 0 on success
 +
|-
 +
| 0x40 || int IOS_IoctlvAsync(int fd, u32 request, u32 vector_count_in, u32 vector_count_out, struct iovec *vector, int queueid, ipcmessage *message) || Async implementation of IOS_Ioctlv || 0 on success
 +
|-
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| 0x41 || || ||
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|-
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| 0x42 || || ||
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|-
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| 0x43 || || ||
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|-
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| 0x44 || || ||
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|-
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| 0x45 || || ||
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|-
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| 0x46 || || ||
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|-
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| 0x47 || || ||
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|-
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| 0x48 || || ||
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|-
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| 0x49 || IOS_ResourceReply(???) || ||
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|-
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| 0x4A || || ||
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|-
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| 0x4B || || ||
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|-
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| 0x4C || || ||
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|-
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| 0x4D || || ||
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|-
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| 0x4E || || ||
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|-
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| 0x4F || || ||
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|-
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| 0x50 || IOS_ClearandEnable(???) || ||
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|-
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| 0x51 || access_iobuf_pool(???) || ||
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|-
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| 0x52 || || ||
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|-
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| 0x53 || || ||
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|-
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| 0x54 || || ||
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|-
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| 0x55 || || ||
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|-
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| 0x56 || || ||
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|-
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| 0x57 || || ||
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|-
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| 0x58 || || ||
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|-
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| 0x59 || || ||
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|-
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| 0x5A || || ||
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|-
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| 0x5B || || ||
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|-
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| 0x5C || || ||
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|-
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| 0x5D || || ||
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|-
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| 0x5E || || ||
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|-
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| 0x5F || || ||
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|-
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| 0x60 || || ||
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|-
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| 0x61 || IOS_CreateSemaphore(???) || ||
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|-
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| 0x62 || IOS_WaitSemaphore(???) || ||
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|-
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| 0x63 || IOS_SignalSemaphore(???) || ||
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|-
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| 0x64 || IOS_DestroySemaphore(???) || ||
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|-
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| 0x65 || || ||
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|-
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| 0x66 || || ||
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|-
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| 0x67 || || ||
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|-
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| 0x68 || || ||
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|-
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| 0x69 || || ||
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|-
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| 0x6A || get_iop_cpu_utilization(???) || ||
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|-
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| 0x6B || || ||
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|-
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| 0x6C || IOS_ThreadProfileCommand(???) || ||
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|-
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| 0x6D || get_thread_utilization(???) || ||
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|-
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| 0x6E || || ||
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|-
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| 0x6F || || ||
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|-
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| 0x70 || || ||
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|-
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| 0x71 || get_iobuf_utilization(???) || ||
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|-
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| 0x72 || get_message_utilization(???) || ||
 +
|-
 +
| 0x73 || get_active_resources(???) || ||
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|-
 +
| 0x74 || || ||
 +
|-
 +
| 0x75 || get_timer_utilization(???) || ||
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|-
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| 0x76 || get_semaphore_utilization(???) || ||
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|-
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| 0x77 || || ||
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|-
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| 0x78 || || ||
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|-
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| 0x79 || || ||
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|-
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| 0x7A || || ||
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|-
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| 0x7B || || ||
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|-
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| 0x7C || || ||
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|-
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| 0x7D || || ||
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|-
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| 0x7E || || ||
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|-
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| 0x7F || panic(???) || ||
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|-
 +
| 0x80 || crash(???) || ||
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|-
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| 0x81 || || ||
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|-
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| 0x82 || || ||
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|-
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| 0x83 || || ||
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|-
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| 0x84 || || ||
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|-
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| 0x85 || || ||
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|-
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| 0x86 || || ||
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|-
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| 0x87 || || ||
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|-
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| 0x88 || || ||
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|-
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| 0x89 || || ||
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|-
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| 0x8A || || ||
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|-
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| 0x8B || || ||
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|-
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| 0x8C || || ||
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|-
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| 0x8D || || ||
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|-
 +
| 0x8E || get_resource_violations(???) || ||
 +
|-
 +
| 0x8F || || ||
 
|-
 
|-
| 10 || int IOS_ReceiveMessage(int queueid, u32 *message, u32 flags) || Fetch a message from the front of a queue || 0 on success
+
| 0x90 || || ||
 
|-
 
|-
| 24 || void* IOS_Alloc(int heapid, u32 size) || Allocate size bytes from the specified heap || pointer to memory
+
| 0x91 || || ||
 
|-
 
|-
| 28 || BOOL IOS_RegisterResourceManager(const char* device, int queueid) || Registers device to the device tree, so it can be opened (from Starlet and PPC) || 0 on success
+
| 0x92 || || ||
 
|-
 
|-
| 2D || int IOS_Open(const char* device, int mode) || Similar to IOS_Open on PPC, except now internal to the IOS system || Returns an fd or error (negative)
+
| 0x93 || || ||
 
|}
 
|}
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