check-trace

Testing & Quality

Analyze the JIT dispatch trace to diagnose boot stalls or crashes

QUICK START

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Prompt to paste

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Source SKILL.md: https://github.com/sebastianbiallas/pearpc/blob/HEAD/.claude/skills/check-trace/SKILL.md

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Check JIT Dispatch Trace

Analyze jitc_trace.log for the pattern or address $ARGUMENTS.

If no argument, check the tail of the trace to diagnose what the CPU is doing.

Steps

Check trace tail (last 30 lines):
```
tail -30 jitc_trace.log
```
Identify the pattern:
- Same 2-3 PCs repeating with MSR_POW (0x4xxxx) → idle loop
- Same 2-3 PCs, DEC frozen → DEC timer not firing
- DEC changes but idle continues → scheduler not switching
- Dispatches to PA 0x00000300 → DSI exceptions
- Dispatches to PA 0x00000900 → DEC interrupts
- Dispatches to PA 0x00000C00 → syscalls (sc instruction)

Count exception dispatches:

grep -c 'pa=00000300' jitc_trace.log   # DSI count
grep -c 'pa=00000900' jitc_trace.log   # DEC count
grep -c 'pa=00000c00' jitc_trace.log   # SC count

If argument is a hex address, search for dispatches to/from that address:
```
grep 'pa=ADDRESS\|ea=ADDRESS' jitc_trace.log | head -20
```
Check DEC timer status:
```
grep '\[DEC\]' BOOT_LOG | tail -5
```
Check WATCH events:
```
grep '\[WATCH\]' BOOT_LOG | tail -10
```

Key fields in trace lines

DISPATCH ea=EFFECTIVE_ADDR pa=PHYSICAL_ADDR msr=MSR_VALUE
SEQ_NUM pc=PA msr=MSR cr=CR lr=LR ctr=CTR r0=R0 r1=SP r2=R2 r3=R3 r4=R4 r5=R5 dec=DEC

ea = effective (virtual) address the kernel sees
pa = physical address after translation
dec = decrementer register value (should change over time)
r1 = stack pointer (0xC01Cxxxx for idle thread, 0xC04Dxxxx for init thread)