Kernel

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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 Module Name Size (bytes)
3.60 SceSysmem SceUIDClass 0x8
3.60 SceUIDDLinkClass 0xC
3.60 SceUIDHeapClass 0xC
3.60 SceUIDFixedHeapClass 0xA4
3.60 SceUIDEntryHeapClass 0xB0
3.60 SceUIDKernelHeapClass 0x80
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 SceUIDPhyMemPartClass 0xAC
3.60 SceUIDSysEventClass 0x20
3.60 SceUIDProcEventClass 0x30
3.60-3.73 SceKernelModulemgr SceUIDModuleClass 0xF4
3.60-3.73 SceUIDLibraryClass 0x10
3.60-3.73 SceUIDLibStubClass 0x10
3.60 SceKernelThreadMgr 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 SceProcessmgr SceUIDProcBudgetClass 0x74
3.60 SceUIDProcessClass 0x4E0
3.60 Unknown SceUIDVSlotClass 0x40
3.60 SceIofilemgr SceUIDVfsFileClass 0x48
3.60 SceUIDIoMountEventClass 0x4C
3.60 SceUIDIoErrorEventClass 0x50
3.60 SceUIDIoAsyncEventClass 0xF8
3.60 SceDisplay SceUIDVblankEventClass 0x38
3.60 Unknown SceUIDCodecEngineMemoryClass 0x34
3.60 Unknown (maybe SceCoredump) SceUIDCafContextClass 0x4E0

Temp

TODO: move these to the appropriate place

SceUIDKernelHeapObject

#define SCE_KERNEL_HEAP_ATTR_AUTO_EXTEND        0x00000001
#define SCE_KERNEL_HEAP_ATTR_UNKNOWN_0x02       0x00000002
#define SCE_KERNEL_HEAP_ATTR_HEAP_CORRUPT_CHECK 0x00000010
#define SCE_KERNEL_HEAP_ATTR_HEAP_AVAILABLE     0x00000020
#define SCE_KERNEL_HEAP_ATTR_EXTEND_LIMIT       0x00000100
#define SCE_KERNEL_HEAP_ATTR_WITH_BASE          0x00000200
#define SCE_KERNEL_HEAP_ATTR_WITH_MEMORY_TYPE   0x00000400
#define SCE_KERNEL_HEAP_ATTR_SOME_SIZE          0x00000800
#define SCE_KERNEL_HEAP_ATTR_IMPORT_FROM_OBJECT 0x00001000

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;
SceUIDProcEventObject
typedef struct SceKernelProcEvent { // size is 0x28-bytes
	struct SceKernelProcEvent *root;
	struct SceKernelProcEvent *next;
	SceUID procEventId;
	void *args;
	int (* create)(SceUID pid, SceProcEventInvokeParam2 *a2, int a3);
	int (* exit)(SceUID pid, SceProcEventInvokeParam1 *a2, int a3);                             // current process exit
	int (* kill)(SceUID pid, SceProcEventInvokeParam1 *a2, int a3);                             // by SceShell
	int (* stop)(SceUID pid, int event_type, SceProcEventInvokeParam1 *a3, int a4);
	int (* start)(SceUID pid, int event_type, SceProcEventInvokeParam1 *a3, int a4);
	int (* switch_process)(int event_id, int event_type, SceProcEventInvokeParam2 *a3, int a4); // switch display frame?
} SceKernelProcEvent;

typedef struct SceUIDProcEventObject { // size is 0x30-bytes
	uintptr_t sce_rsvd[2];
	SceKernelProcEvent procEvent;
} SceUIDProcEventObject;
SceUIDSysEventObject
typedef struct SceKernelSysEvent { // size is 0x18-bytes
	struct SceKernelProcEvent *root;
	struct SceKernelProcEvent *next;
	SceUID sysEventId;
	SceSysEventHandler handler;
	void *args;
	SceUInt32 unused;
} SceKernelSysEvent;

typedef struct SceUIDSysEventObject { // size is 0x20-bytes
	uintptr_t sce_rsvd[2];
	SceKernelSysEvent sysEvent;
} SceUIDSysEventObject;

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.