Kernel

The PS Vita has a purely modular kernel. All components of the kernel are .skprx files found in the os0: partition and are listed in Modules.

UID

Class

Version	Name	Size (bytes)
3.60	SceUIDClass	0x8
3.60	SceUIDDLinkClass	0xC
3.60	SceUIDHeapClass	0xC
3.60	SceUIDFixedHeapClass	0xA4
3.60	SceUIDEntryHeapClass	0xB0
3.60	SceUIDSysrootClass	0x41C
3.60	SceUIDSimpleMemBlockClass	0x40
3.60	SceUIDMemBlockClass	0x40
3.60	SceUIDTinyPartitionClass	0x38
3.60	SceUIDPartitionClass	0x80
3.60	SceUIDAddressSpaceClass	0x170
3.60-3.73	SceUIDModuleClass	0xF4
3.60-3.73	SceUIDLibraryClass	0x10
3.60-3.73	SceUIDLibStubClass	0x10
3.60	SceUIDPhyMemPartClass	0xAC
3.60	SceUIDSysEventClass	0x20
3.60	SceUIDProcEventClass	0x30
3.60	SceUIDCacheClass	0x10
3.60	SceUIDWaitableClass	0x28
3.60	SceUIDThreadClass	0x200
3.60	SceUIDFastMutexClass	0x80
3.60	SceUIDCallbackClass	0x80
3.60	SceUIDRegisterCallbackClass	0x30
3.60	SceUIDThreadEventClass	0x80
3.60	SceUIDEventFlagClass	0x80
3.60	SceUIDSemaphoreClass	0x80
3.60	SceUIDMutexClass	0x80
3.60	SceUIDCondClass	0x80
3.60	SceUIDEventClass	0x38
3.60	SceUIDMsgPipeClass	0x80
3.60	SceUIDLwMutexClass	0x80
3.60	SceUIDLwCondClass	0x80
3.60	SceUIDRWLockClass	0x80
3.60	SceUIDSimpleEventClass	0x80
3.60	SceUIDWorkQueueClass	0x80
3.60	SceUIDWorkTaskClass	0x80
3.60	SceUIDExceptionClass	0x80
3.60	SceUIDCpuTimerClass	0x58
3.60	SceUIDDelayClass	0x80
3.60	SceUIDAlarmClass	0x80
3.60	SceUIDTimerClass	0x80
3.60	SceUIDProcBudgetClass	0x74
3.60	SceUIDProcessClass	0x4E0
3.60	SceUIDVSlotClass	0x40
3.60	SceUIDVfsFileClass	0x48
3.60	SceUIDIoMountEventClass	0x4C
3.60	SceUIDIoErrorEventClass	0x50
3.60	SceUIDIoAsyncEventClass	0xF8
3.60	SceUIDVblankEventClass	0x38
3.60	SceUIDCodecEngineMemoryClass	0x34
3.60	SceUIDCafContextClass	0x4E0

Temp

TODO: move these to the appropriate place

SceUIDKernelHeapObject

typedef struct SceKernelHeap { // size is 0x78-bytes
    uintptr_t unk_0x00;
    int cpu_intr;
    uintptr_t unk_0x08[2];
    SceUInt32 attr;
    SceSize unk_0x14; // from opt.field_14
    SceUInt32 heap_memory_type;
    SceSize unk_0x1C; // from opt.field_8
    SceSize heapSize1;
    SceSize heapSize2;
    SceUInt32 currentHeapCount;
    SceUInt32 maximumHeapCount;
    SceSize currentHeapUsedSize;
    SceSize maximumHeapUsedSize;
    SceSize maximumRequestSize;
    void *pWorkingArea; // for internal
    char *name;
    void *data_0x44;
    SceUInt32 unk_0x48;
    SceUInt32 unk_0x4C[0xB]; // zeros
} SceKernelHeap;

typedef struct SceUIDKernelHeapObject { // size is 0x80-bytes
    union {
        uintptr_t sce_rsvd[2];
        struct {
            void *pUserdata;
            SceClass *pClass;
        };
    };
    SceKernelHeap kernelHeap;
} SceUIDKernelHeapObject;

UID Attr

     Mask   Description
  0x70000 |   vis_level
 0x300000 |   act entry

GUID

Global UID.

0 0 00 0000 0000 0001 0000 0000 0000 000 1

Error bit. should be 0.

PUID bit. should be 0.

Sub UID. 14-bits wide. Has no effect directly for core uid. Somewhat random values are used for security (With increase method).

Core UID. 15-bits wide. Value to identify the object.

UID bit. should be 1.

The Core UID is 15-bits so in theory the system can create to 0x8000 (32768) objects

Example : 0x10005, 0x10007, 0x10547, 0x2DF84A9

PUID

Process UID.

0 1 00 0000 0000 0001 0000 0000 0000 000 1

Error bit. should be 0.

PUID bit. should be 1.

Unknown. maybe sub UID. 14-bits wide.

Unknown. maybe core UID. 15-bits wide.

UID bit. should be 1.

Example : 0x40010001

Security

KASLR

Since PS Vita FW 1.80 or so, the kernel implements kernel address space layout randomization to discourage ROP attacks.

Canaries

Since PS Vita FW 1.80 or so, the kernel makes use of stack canaries to detect stack buffer overflows and halts the system when an overflow is detected.

Memory Domains

Memory domains is a feature in ARM MMU that provides an easy way of showing and hiding groups of addresses as well as their permissions. When a syscall is made, the handler disables all access to memory domains for user memory so kernel code cannot directly access user memory. This means if a user pointer is passed in and the kernel forgets to check it and dereferences it directly, it will abort. In order to access user memory, special functions are used that temporarily enables all domains and the access is implemented with the ARM unprivileged access instructions LDRT and STRT to make sure the access functions cannot read or write in kernel memory space. As long as the domain disable code in the syscall hander is secure and the user memory access functions are secure, there is no need for additional checks implemented per function. Additionally all non-code pages are marked as "execute never" (XN) in both kernel and usermode.

Syscall Randomization

The numbers assigned to syscalls change on each boot but the delta between the same functions exported by the same module will stay consistent.

NID Poisoning

Since PS Vita FW 2.10, SceKernelModulemgr replace the NIDs entries in the module import tables with junk data. This means that you can no longer map syscall numbers to NIDs.

Usermode stack pivoting protection

Since unknown PS Vita FW version (seen on 3.18) the kernel terminates an application if it notices that its stack pointer register (SP) is not pointing into the stack memory. This is commonly named "SMAP" on Linux where it crashes when Kernel stack pointer points to usermode memory.

User and kernel heap overflow protection

dlmalloc, used for heap allocations, is compiled with -DFOOTERS=1 to enable more heap overflow checks. Additionally, a custom SceNetPs malloc implementation also does some heap overflow checks on its own.

List of kernel modules

For a list of all kernel modules, check out Modules.