Kernel

Source: https://blog.siguza.net/APRR/

Security

panic(cpu 0 caller 0xfffffff01dd79b84): "Undefined kernel instruction: pc=0xfffffff01dbd8084 instr=d518c000\n"
Debugger message: panic
Memory ID: 0xff
OS version: 16A405
Kernel version: Darwin Kernel Version 18.0.0: Tue Aug 14 22:07:18 PDT 2018; root:xnu-4903.202.2~1/RELEASE_ARM64_T8020
Kernel UUID: BEFBC911—B1BC-3553—B7EA-1ECE60169886
iBoot version: iBoot-4513.200.297
secure boot?: YES
Paniclog version: 10
Kernel slide: 0x0000000016200000
Kernel text base: 0xfffffff01d204000
Epoch Time:        sec       usec
  Boot    : 0x5cc4e1ec 0x000c74d9
  Sleep   : 0x00000000 0x00000000
  Wake    : 0x00000000 0x00000000
  Calendar: 0x5cc4e21d 0x000d3015

panic(cpu 0 caller 0xfffffff01dd79b84): "Undefined kernel instruction: pc=0xfffffff01dbd8084 instr=d518c000\n"

The panic line is the kernel’s way of saying “I tried to do something I wasn’t allowed to do, and I have no way to recover.” It tells you it happened on CPU 0 and even gives the address in the kernel code (caller 0xfffffff01dd79b84) where it decided to abort. Then it reports that at instruction address 0xfffffff01dbd8084 the CPU tried to execute the opcode d518c000, which, when decoded, is the privileged instruction msr vbar_el1, x0. On newer Apple chips, writes to system registers like VBAR_EL1 are blocked by the hardware’s permission-indirection layer, so attempting that write raises an “undefined instruction” exception. Because the kernel didn’t have any special handler for that trap, it fell into its built-in panic routine and printed out this diagnostic.

UUID

The Kernel UUID is a globally unique identifier (GUID) baked into that specific kernel build, used by symbolication and debugging tools to match panic logs and crash dumps to the exact kernel binary and its debug symbols.

Kernel slide

The kernel slide is the random per-boot offset added to the kernel’s preferred base address as part of Kernel Address Space Layout Randomization (KASLR), so that the actual in-memory location of the kernel (and its data structures) differs each boot, making targeted exploits much harder.