S5L8900

This is the Application Processor shared between the iPhone, iPod touch, and the iPhone 3G. Not much is known about it through official sources. This processor is not used in any of the newest devices, being replaced by the S5L8720 and S5L8920.

Exploits

iBoot

Note: iBoot on the S5L8720 can be downgraded, allowing any of these exploits to be used on future firmwares

• Restore Mode - Works up to iOS 1.0.2
• Ramdisk Hack - Works up to iOS 2.0 beta 3
• diags - Works up to iOS 2.0 beta 5
• ARM7 Go - Works on iOS 2.1.1
• iBoot Environment Variable Overflow - Works up to iOS 3.1 beta 3
• usb_control_msg(0x21, 2) Exploit - Works up to iOS 3.1.2

Bootrom

• Pwnage 1.0 (Ramdisk + AppleImage2NORAccess)
• Pwnage 2.0 (DFU + Malformed Certificate)

Kernel

• BPF STX Kernel Write Exploit - Works up to iOS 3.1.3
• IOSurface Kernel Exploit - Works up to iOS 4.0.1

Userland

• Symlinks - Works up to iOS 1.1.1
• LibTiff - Works up to iOS 1.1.1
• Mknod - Works up to iOS 1.1.2
• Dual Boot Exploit - Works up to iOS 2.0 beta 3
• MobileBackup Copy Exploit - Works up to iOS 3.1.3
• PDF CFF Font Stack Overflow - Works up to iOS 4.0.1

Boot Chain

VROM->LLB->iBoot->Kernel->System Software

One of the iPhoneLinux goals are to replace that Boot Chain after iBoot:
VROM->OpeniBoot->Linux Kernel->X Server->Window Manager

Upgrade Process

Restore Mode

The common upgrade process chain is VROM->DFU->WTF->iBoot->Kernel->Ramdisk->Restore Mode.

DFU Mode

To flash an older version of the iPhone software you have to let your phone reside in DFU. In iTunes you have to press the option key (Mac) or the shift key (Windows) when pressing 'Restore' to be able to manually chose an IPSW.

Boot Chain

VROM->DFU

External Links

• Technical Reference Manual: ARM1176JZF-S