SceExcpmgr

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SceExcpmgr is a kernel module that sets up exception handling and a version exists in both worlds. In non-secure world, after the kernel is booted up, the exception handlers pointed to by VBAR all jump into code in this module.

Module

This module exists in both non-secure and secure world. The non-secure world SELF can be found in os0:kd/sysmem.skprx.

Known NIDs

Version Name World Privilege NID
1.69 SceExcpmgr Non-secure Kernel 0xBBCA9AB6
1.69 SceExcpmgr Secure Kernel 0x93332B9A

Libraries

This module only exports kernel libraries.

Known NIDs

Version Name World Visibility NID
1.69 SceExcpmgrForKernel Non-secure Kernel 0x4CA0FDD5
1.69 SceExcpmgrForTZS Secure Kernel 0x8F526F35

SceExcpmgrForKernel

ksceKernelRegisterPriorityExceptionHandler

Version NID
3.60 0x03499636

Installs an exception handler.

int SceExcpmgrForKernel_03499636(int excpcode, int priority, void *function)

The function must be ARM and not thumb, and the allowed priority values are from 0 to 7 (including them).

Where excpcode can be:

  • Reset: excpcode = 0
  • Undefined Instruction: excpcode = 1
  • Supervisor Call: excpcode = 2
  • Prefetch Abort: excpcode = 3
  • Data Abort: excpcode = 4
  • Not used: excpcode = 5
  • IRQ interrupt: excpcode = 6
  • FIQ interrupt: excpcode = 7

SceExcpmgrForTZS

Exceptions

SVC

The Syscalls interface is defined in non-secure kernel as:

Register Value
R0 First argument
R1 Second argument
R2 Third argument
R3 Fourth argument
R12 Syscall number

On return, R1-R3 and R12 are cleared to 0x0 or 0xDEADBEEF to prevent any data leaks. All user pointers passed to syscalls are accessed with ARM instructions LDRT and STRT for hardware forced permission checks. Syscalls 0x0 - 0xFF are likely a "fastcall" interface that do not mask interrupts or set the DACR, however currently are no such fastcalls defined. Syscalls 0x100 - 0xFFF are made with IRQ interrupts masked and DACR set to 0xFFFF0000 (to prevent access to certain memory domains). Any other syscall numbers are invalid.

System calls are handled in "system" mode defined in ARMv7 (mode 0b11111).

User exported functions loaded by SceKernelModulemgr are exported as syscalls. The number assigned to the syscall are randomized with respect to each library but not within a library. That means, for example, two functions exported by a library will always be some syscall number apart even though that number will change on each boot.

There is no SVC in secure world because all code in secure world is running as kernel.

SMC

The SMC interface for making a non-secure kernel call to secure-kernel is:

Register Value
R0 First argument
R1 Second argument
R2 Third argument
R3 Fourth argument
R12 Secure service number

The SMC interface is very similar to SVC from userland to non-secure kernel. The SMC handler and MVBAR is set up in secure world by SceExcpmgrForTZS. 0x0 - 0xFF are fast service calls. 0x100 - 0xFFF are normal service calls ran with IRQs masked.

Secure services are ran in ARM system processor mode (0b11111) in the secure world.

SMC calls are registered by SceIntrmgrForTZS.

SMC calls

Number Arguments Notes
0x103
int disable_virtual_ranges(void);
Disables the virtual ranges: 0x40000000-0x40100000, 0x50000000-0x51000000 and 0x51000000-0x52000000 to the context with PID 0x10007.
0x10F
int smc_0x10F(void);
Cleans and invalidates all the L1 Dcache and invalidates(and cleans?) the unknown coprocessor cache.
0x114
int smc_0x114_bus_freq_op(int operation, unsigned int freq);
op = 0: Set bus frequency, op = 1: Get bus frequency, op = 2: Set GPU Xbar frequency, op = 3: Get GPU Xbar frequency
0x117
int cdram_enable(void);
0x118 CDRAM related
0x119 CDRAM related
0x11A
int reset_device(int type, int unk);
Reset device (check [1] for more info).
0x11D
int mips_set_memory_bank_start_paddr(int bank, unsigned int paddr);
Valid banks 0-7, and paddrs: 0x20000000-0x2FFFFFFF and 0x42800000-0x7FFFFFFF.
0x120
int mips_get_memory_bank_start_paddr(int bank);
Valid banks 0-7.
0x12D
int smc_sm_sched_proxy_invoke(int priority, uintptr_t paddr, unsigned int num_pairs, int unk);
Used by sceSblSmSchedProxyInvoke.
0x12E Used by sceSblSmSchedProxyWait.
0x12F Used by sceSblSmSchedProxyGetStatus.
0x130 SBL SM Sched related
0x133
int sbl_sm_sched_call_func(int id, int unk, uintptr_t cmd_paddr);
Used by sceSblSmSchedCallFunc. cmd_paddr is paddr(SceSblSmschedCallFuncCommand) | 1.
0x134 SBL SM Sched related
0x135 SBL SM Sched related
0x136 SBL SM Sched related
0x137 SBL SM Sched related
0x138 SBL SM Sched related
0x139 SBL SM Sched related
0x13A SBL SM Sched related. Interrupt Cry2Arm set enable.
0x13B SBL SM Sched related. Interrupt Cry2Arm clear enable.
0x13C SBL SM Sched related. Waits polling.
0x16A
int l2_write_control_register(int value);
0x16B
int l2_write_auxiliary_control_register(int value);

Aborts

On development units, data and prefetch aborts can handle BKPT instruction for software breakpoints. SceDebug uses this to handle usermode breakpoints. There is no built-in support for BKPT in kernel code.

SceSysmem uses data aborts with the LDRT and STRT instructions to implement user pointer checking. When LDRT/STRT throws a MMU data exception because of an invalid access and the exception came from the sceKernelMemcpyUserToKernel or sceKernelMemcpyKernelToUser (or related functions), the data abort handler will resume execution.

IRQ

IRQs are only handled in non-secure world. An IRQ in secure world is fatal. See SceKernelIntrMgr.

FIQ

FIQs are only handled in secure world because of the bit set in the SCR. Because of this, it is likely that secure devices such as the F00D Processor use FIQs to communicate with the Cortex A9 cores. See SceKernelIntrMgr.