Boot Sequence

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Boot Process

Syscon

Syscon powers up and sets up DRAM, sets up boot context buffer, turns on the F00D processor that starts the Boot ROM.

Boot ROM

The PSVita 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 F00D processor is the actual secure boot device rather than the ARM processor. The F00D processor bootrom ("first loader") is the first code running on PSVita start. Once it starts it likely maps the eMMC and directly reads in the second_loader.enp or second_loader.enp_ from the eMMC SLB2 partition. This is in the native load format of the F00D bootrom. There are 2 layers of encryption. First it decrypts the per-console layer that was added during the firmware installation. After that it decrypts the factory-encrypted layer then begins execution. See Enc.

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 or enp_ binary.

F00D processor then restarts and loads the secure_kernel.enp in and again decrypts the per-console layer that was added during the firmware install, and the factory layer. At this point the F00D processor is prepared and Secure Kernel tells Syscon to reset the ARM CPU at 0x00000000 (F00D scratch buffer). This triggers the ARM secure boot process.

Secure Kernel Bootloader

The secure kernel bootloader decompresses the ARZL compressed TrustZone, 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. 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 special case

On FW 0.931, 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.

Boot Partition

The boot partition is SLB2 formatted. It contains entries these files:

Name Earliest Known Version Comments
kernel_boot_loader.self 0.931 Secure KBL and ARZL compressed NS KBL
kprx_auth_sm.self 0.931 Used with F00D Processor to decrypt SELFs
prog_rvk.srvk 0.931 SCE encrypted SELF revocation list
second_loader.enp 0.931 Secure bootloader
second_loader.enp_ 0.931 Related to second_loader.enp in some way, likely for encryption
secure_kernel.enp 0.931 Secure kernel loader
secure_kernel.enp_ 0.931 Related to secure_kernel.enp in some way, likely for encryption
secure_kernel.xxx 0.931 Prototype secure kernel loader encrypted differently than secure_kernel.enc

System Configuration Script

also see : SceSysStateMgr

os0:psp2config.skprx once decrypted is a UTF-8 text file that is parsed by SceSysStateMgr. It is a very simple script format.

If "Producting Mode" (MANUFACTURING_MODE) is enabled, then it is possible to load psp2config.skprx from sd0: (SD adapter in GameCard slot) or ux0:. However, the files must still be signed and encrypted SELFs. In "Producting Mode" if sd0:psp2diag.self or ux0:psp2diag.self exists (and is a valid signed & encrypted SELF), then it will be launched. If "Development Mode" (DEVELOPMENT_MODE) is enabled (note that this does not necessarily mean PDEL or devkit), then psp2config.skprx can be a plaintext file instead.

Comments

Comments start out with #.

As an example, here is the header of FW 1.69 psp2config.skprx:

#
# PSP2 System Configuration for Release
#
# [NOTICE]
# 
# This configuration is only for kernel_boot_loader_release.self.
#

Conditionals

Conditionals start with if and end with endif. There are certain conditional constants defined in SceSysStateMgr. A table of known conditionals is below.

Name Description
MANUFACTURING_MODE When the unit is in Manufacturing Mode (enabled by Jig), it tries to load psp2diag.self from sd0: or ux0:. This a diagnosis tool (this file has never been leaked). This info comes from NVS.
EXTERNAL_BOOT_MODE If set, SceSysStateMgr skips bootimage.skprx load. Depends on some condition set on boot by some bootloader
UPDATE_MODE Set by Syscon when an update is about to be performed. This info comes from NVS. In this case, psp2swu.self is loaded.
USB_ENUM_WAKEUP This flag is set when the PSVita boots due to USB CMA connection while device is turned off or USB automatic boot in IDU mode.
KERMIT_REV_ES1_X GPU hardware revision related. Does not support the Home Menu. Loads vs0:vsh/shell/shell_mini.self instead of shell.self.
KERMIT_REV_ES2_X GPU hardware revision related.
KERMIT_REV_ES3_X GPU hardware revision related.
KERMIT_REV_ES4_X GPU hardware revision related.
KERMIT15_REV_ES1_X Unknown.
KERMIT10_REV_ES4_X Unknown.
UD0_EXIST Does the ud0: Partition exist. This info comes from ?sceIoGetstatForDriver?.
DEMO_MODE Is the PSVita IDU Mode / Show Mode flagged. This info comes from Syscon.
BSOD_REBOOT Must the PSVita boot in BSOD mode? This info comes from NVS. In this case, os0:kd/crashdump.skprx is loaded. Once the home menu appears a warning message about bad shutdown risks is displayed.
SAFE_MODE Is the PSVita in safe mode. This info comes from NVS. In this case, os0:ue/safemode.self is loaded.
DEVELOPMENT_MODE SceSblACMgr is called to check if device is a development device and is in DevMode. This info comes from CP DIP Switches.
AU_CODEC_IC_CONEXANT An audio IC chip from CONEXANT that could be seen only on PSVita (not PSTV) CEX and DEX (not TOOL) units. This info comes from KBL Param#Hardware_flags. In this case, codec_cx.skprx is loaded instead of codec.skprx.

Example:

if SAFE_MODE
spawn	os0:ue/safemode.self
end
endif

Spawn

spawn path will spawn an app and continue processing the script in the background.

spawnwait path will spawn an app and wait for it to exit before continuing processing the script.

appspawn path param is used to spawn the app self located at path with the parameter param.

Known param constants:

Name Description
SHELL_BUDGET_ID Unknown. Example modules: vs0:vsh/shell/shell.self and vs0:vsh/shell/shell_mini.self
GAME_BUDGET_ID Unknown. Example module: vs0:vsh/shell/shell_gamebudget.self

All codes (from FW 0.990)

load, unload, loadonly, start, stop, unloadonly, spawn, spawnwait, wait, kill, loadconfig, ifmodel, ifnmodel, setenv, setmodfile, repeat, endrepeat, appspawn, tload

+ include, if, endif, end

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.

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

Code Location Description
65 / 0x41 second_loader Hardware Info some check complete
67 / 0x43 second_loader Register bigmac key 0x508 and 0x51B complete
68 / 0x44 second_loader Unknown
69 / 0x45 second_loader Unknown
70 / 0x46 second_loader Setting qa flags to bigmac keyring complete
72 / 0x48 ? ?
82 / 0x52 second_loader Emmc is not available
84 / 0x54 ? ?
85 / 0x55 second_loader Setting factory fw to bigmac keyring complete
86 / 0x56 ? ?
90 / 0x5A second_loader Setting SceKblParam
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. Or undefined instruction exception.
139 / 0x8B Secure Kernel BootLoader SVC exception (should not happen, error)
140 / 0x8C Secure Kernel BootLoader Prefetch abort exception
141 / 0x8D Secure Kernel BootLoader Data abort exception
142 / 0x8E Secure Kernel BootLoader IRQ exception (should not happen, error)
143 / 0x8F Secure Kernel BootLoader FIQ exception (should not happen, error)
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 Undefined instruction exception
171 / 0xAB Non-Secure Kernel BootLoader SVC exception (should not happen, error)
172 / 0xAC Non-Secure Kernel BootLoader Prefetch abort exception
173 / 0xAD Non-Secure Kernel BootLoader Data abort exception
174 / 0xAE Non-Secure Kernel BootLoader IRQ exception (should not happen, error)
175 / 0xAF Non-Secure Kernel BootLoader FIQ exception (should not happen, error)

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 Suspend.