Boot Sequence

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Boot Process

Syscon

Syscon powers up and sets up DRAM, sets up boot context buffer, turns on the KERMIT SOC which eventually starts the Boot code on the CMeP Processor.

First Loader

The PS Vita main application processor is an ARM Cortex A9 MPcore. It implements ARM TrustZone for execution in both a non-secure world and a sandboxed Secure World. However it is not the first processor to run on boot.

The cmep processor is the actual secure boot device rather than the ARM processor. The cmep processor's boot ROM, nicknamed First Loader, is the first known code running on PS Vita start. Once it starts, it likely maps the eMMC and directly reads in the second_loader.enp from the eMMC (SLB2 partition) or SD Card (if SD BOOT challenge passes). This is in the native load format of the boot ROM. There are two layers of encryption. First it decrypts the per-console SLSK personalization layer that was added during the System Software installation. After that, it decrypts the factory-encrypted SLSK layer then begins execution.

Second Loader

The Second Loader is primarily responsible for preparing the ARM processor. It initializes DRAM and decrypts kernel_boot_loader.self from eMMC SLB2 partition into DRAM. It also writes the ARM exception vector and some boot context information to the 32kB scratch buffer (mirror mapped to 0x00000000 on ARM). kernel_boot_loader.self contains both the secure kernel bootloader and TrustZone, as well as the non-secure kernel bootloader. At this point the kprx_auth_sm.self and prog_rvk.srvk read from the eMMC SLB2 partition are both loaded into DRAM. Finally, the Second Loader resets itself with a pointer to the secure_kernel.enp binary.

Secure Kernel

the cmep processor then restarts and loads the secure_kernel.enp in and again decrypts the per-console layer that was added during the System Software installation, and the factory layer. At this point the cmep processor is prepared and Secure Kernel tells Syscon to reset the ARM CPU at 0x00000000 (cmep scratch buffer). This triggers the ARM secure boot process.

Secure Kernel Bootloader

The secure kernel bootloader decompresses the ARZL compressed TrustZone kernel, loads it and sets up the VBAR and MVBAR. It then decompresses the ARZL non-secure kernel bootloader, sets NS in SCR and jumps into non-secure kernel bootloader with svc mode. See Kernel Boot Loader for more information.

Non-secure Kernel Bootloader

The non-secure kernel bootloader contains an embedded and likely stripped version of SceSysmem, SceKernelModulemgr, SceSblSmschedProxy, and some other core drivers. The NSKBL sets up the eMMC device (again) and starts os0:psp2bootconfig.skprx.

ScePsp2BootConfig

This kernel module does not export any library. It only has a module init function that has a hard coded list of core kernel modules (ex: sysmem.skprx) which are loaded with calls back into NSKBL through SceKblForKernel imports. Once the core initialization is done, the next module to run is SceSysStateMgr.

FW 0.931.010 special case

On System Software version 0.931.010 (and probably earlier versions), NSKBL embeds the kernel modules list in data segment instead of using the ScePsp2BootConfig kernel module. Here is the list: 

sysmem.skprx

excpmgr.skprx

intrmgr.skprx

systimer.skprx
acmgr.skprx
threadmgr.skprx
dmacmgr.skprx

ssproxy.skprx

smsc_proxy.skprx

authmgr.skprx

iofilemgr.skprx
modulemgr.skprx
processmgr.skprx

backtrace.skprx
sdbgsdio.skprx
deci4p_sdfmgr.skprx
deci4p_sttyp.skprx
deci4p_sdbgp.skprx
deci4p_sdrfp.skprx
stdio.skprx
lowio.skprx
clockgen.skprx
sdif.skprx
sdstor.skprx

fatsd.skprx
exfatfs.skprx

pamgr.skprx
sysstatemgr.skprx

SceSysStateMgr

This kernel module also does not export any library. Its init function first maps all the SceKernelBootimage embedded modules and redirects them to os0:kd/. Then it decrypts os0:psp2config.skprx or os0:psp2config_vita.skprx or os0:psp2config_dolce.skprx and parses the System Configuration Script to load the remaining modules and finally either SceSafemode or SceShell or ScePsp2Swu or ScePsp2Diag.

Also refer to the SceSysStateMgr page for System Configuration Script.

Boot Partition

The boot partition, named sloader, is SLB2 formatted.

Boot Debug Checkpoint Codes

During the boot sequence, the various bootloaders will update a GPIO register specifying the progress into boot. This can be used to debug where in the boot process something fails.

Second Loader checkpoint codes start at 0x40 (e.g. GPO value 0x52 corresponds to SBL code 0x12).

GPIO

The GPIO registers are registered at 0xE20A000C (turn off bits) and 0xE20A0008 (turn on bits). On PDEL units, this maps to the LED lights.

Known Codes

The Event column indicates what happens/is about to happen when a code is shown on the GPO LED. If boot of the unit doesn't succeed, the Halting event column indicates what caused the boot process to fail based on the last value of the GPO LED.

Code Location Event Halting event
64 / 0x40 second_loader (0.931.010) SBL finished successfully
65 / 0x41 second_loader Some Hardware Info check complete - GPO intiailization OK?
66 / 0x42 second_loader (0.931.010) Something with Syscon ERROR: communication with Syscon failed
67 / 0x43 second_loader Register bigmac key 0x508 and 0x51B complete ERROR: communication with Syscon failed
68 / 0x44 second_loader ERROR: ?some check with keyring 0x501 and Cmep data? failed
69 / 0x45 second_loader ?Initializing LPDDR2? ERROR: ?LPDDR2 initialization failed?
70 / 0x46 second_loader Setting QA flags to bigmac keyring complete
71 / 0x47 second_loader (0.931.010) Calling testMemory ?ERROR: testMemory failed?
72 / 0x48 second_loader (0.931.010) ?Initializing SD/eMMC? ERROR: ?SD/eMMC initialization failed?
73 / 0x49 second_loader (0.931.010) ?Loading kernel_boot_loader.self? ERROR: ?reading/loading/... kernel_boot_loader.self failed?
74 / 0x4A second_loader (0.931.010) ERROR: ?SD/eMMC I/O error?
75 / 0x4B second_loader (0.931.010) WARNING: Reading ConsoleID from eMMC failed
76 / 0x4C second_loader (0.931.010) ERROR: ?starting ARM clock failed? (cannot happen on System Software version 0.931.010)
77 / 0x4D second_loader (0.931.010) ?Initializing SNVS? ERROR: Writing 0x502-0x504/0x50B/... keyring failed (?SNVS init failed?) (cannot happen on System Software version 0.931.010)
78 / 0x4E second_loader (0.931.010) ERROR: SBL version mismatch with SVNS-stored System Software version
79 / 0x4F second_loader (0.931.010) ERROR: testMemory failed (dummy in System Software version 0.931.010, cannot happen)
80 / 0x50 second_loader (0.931.010) Copying keyrings 0x602/0x601 to physical address 0xE0020100/0xE0020200
82 / 0x52 second_loader ERROR: eMMC is not available
83 / 0x53 second_loader WARNING: Reading OpenPSID from eMMC failed
84 / 0x54 second_loader ERROR: Minimal System Software version read failed / SBL version is lower than minimal System Software version
85 / 0x55 second_loader Setting factory System Software version to Bigmac keyring complete WARNING: Something related to Syscon communication failed?
86 / 0x56 second_loader
87 / 0x57 second_loader (0.931.010) WARNING: ???
88 / 0x58 second_loader (0.940) WARNING: invalid/mismatched per-console information?
89 / 0x59 second_loader (0.931.010) WARNING: ???
90 / 0x5A second_loader About to write SceKblParam to SPAD32K
94 / 0x5E second_loader (0.931.010) ERROR: SVNS-stored System Software version is lower than minimal System Software version
96 / 0x60 second_loader Setting SceKblParam complete and Start setting some device clock.
129 / 0x81 Secure Kernel BootLoader Core 0 (secure world) pre-init complete
130 / 0x82 Secure Kernel BootLoader Secure world interrupts registered (?)
131 / 0x83 Secure Kernel BootLoader Serial console ready, boot message printed
132 / 0x84 Secure Kernel BootLoader Some device init
133 / 0x85 Secure Kernel BootLoader Some co-processor init. Starting point for other cores.
134 / 0x86 Secure Kernel BootLoader MMU enabled, VBAR/MVBAR set up
135 / 0x87 Secure Kernel BootLoader Nothing since 134
136 / 0x88 Secure Kernel BootLoader Boot setup complete, secure kernel loading begin
137 / 0x89 Secure Kernel BootLoader Secure kernel loaded. About to load NS KBL at 0x51000000
138 / 0x8A Secure Kernel BootLoader Secure kernel loaded. About to resume context at 0x1F000000. ERROR: Undefined Instruction exception
139 / 0x8B Secure Kernel BootLoader ERROR: SVC exception (should not happen)
140 / 0x8C Secure Kernel BootLoader ERROR: Prefetch abort exception
141 / 0x8D Secure Kernel BootLoader ERROR: Data abort exception
142 / 0x8E Secure Kernel BootLoader ERROR: IRQ exception (should not happen)
143 / 0x8F Secure Kernel BootLoader ERROR: FIQ exception (should not happen)
161 / 0xA1 Non-Secure Kernel BootLoader Core 0 (non-secure world) pre-init complete
162 / 0xA2 Non-Secure Kernel BootLoader Some interrupts registered (?)
163 / 0xA3 Non-Secure Kernel BootLoader Serial console ready, boot message printed (if enabled)
164 / 0xA4 Non-Secure Kernel BootLoader Some buffer is initialized to device addresses
165 / 0xA5 Non-Secure Kernel BootLoader Some co-processor init. Starting point for other cores.
166 / 0xA6 Non-Secure Kernel BootLoader MMU enabled, VBAR set up
167 / 0xA7 Non-Secure Kernel BootLoader Nothing since 166
168 / 0xA8 Non-Secure Kernel BootLoader Boot setup complete, NS kernel loading begin
169 / 0xA9 Non-Secure Kernel BootLoader Kernel pre-init (setup stacks, interrupts, etc) done. Right before first external loading.
170 / 0xAA Non-Secure Kernel BootLoader ERROR: Undefined Instruction exception
171 / 0xAB Non-Secure Kernel BootLoader ERROR: SVC exception (should not happen)
172 / 0xAC Non-Secure Kernel BootLoader ERROR: Prefetch abort exception
173 / 0xAD Non-Secure Kernel BootLoader ERROR: Data abort exception
174 / 0xAE Non-Secure Kernel BootLoader ERROR: IRQ exception (should not happen)
175 / 0xAF Non-Secure Kernel BootLoader ERROR: FIQ exception (should not happen)

Suspend and Resume

Upon suspension, context is written to memory and a syscon command is issued to save the context pointer as well as other information (for example, if it should restart into update mode). When resuming, the boot process is the same as cold boot up until the secure kernel bootloader. After secure kernel loads, instead of decompressing and jumping to the non-secure kernel bootloader, it restores the saved context and returns to the kernel resume code.

See also Suspend.

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