Allow tracing kernel threads - #385
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When attaching to a kernel thread, /proc/$pid/exe is unavailable. Detect kernel threads by ppid=kthreadd (PID 2) and resolve symbols from vmlinux instead. Show kernel threads in the fzf attach picker and require kernel tracing flags when attaching to them. Fixes janestreet#226 Signed-off-by: Nehal Singhal <nehalsinghal06@gmail.com>
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Summary
/proc/$pid/exe.-trace-include-kernelor-trace-kernel-onlywhen attaching to them.Fixes #226
Reproduction
On this WSL2 system, kernel thread PID 342 has
ppid=2andreadlink /proc/342/exefails. Before this change,magic-trace attach -pid 342would fail when resolving the executable path.Test plan
/proc/$pid/statppid parsing andis_kernel_threadon the current process.dune runtest(requires opam switch with project dependencies).magic-trace attach -pid <kernel-thread-pid> -trace-kernel-only, snapshot with Ctrl-C, verify trace decodes with kernel symbols.Signed-off-by: Nehal Singhal nehalsinghal06@gmail.com