17.6.1.3.2. Exit gem5 on panic
gem5 9048ef0ffbf21bedb803b785fb68f83e95c04db8 (January 2019) can detect panics automatically if the option system.panic_on_panic is on.
It parses kernel symbols and detecting when the PC reaches the address of the panic function. gem5 then prints to stdout:
Kernel panic in simulated kernel
and exits with status -6.
At gem5 ff52563a214c71fcd1e21e9f00ad839612032e3b (July 2018) behaviour was different, and just exited 0: https://www.mail-archive.com/gem5-users@gem5.org/msg15870.html TODO find fixing commit.
We enable the system.panic_on_panic option by default on arm and aarch64, which makes gem5 exit immediately in case of panic, which is awesome!
If we don’t set system.panic_on_panic, then gem5 just hangs on an infinite guest loop.
TODO: why doesn’t gem5 x86 ff52563a214c71fcd1e21e9f00ad839612032e3b support system.panic_on_panic as well? Trying to set system.panic_on_panic there fails with:
tried to set or access non-existentobject parameter: panic_on_panic
However, at that commit panic on x86 makes gem5 crash with:
panic: i8042 "System reset" command not implemented.
which is a good side effect of an unimplemented hardware feature, since the simulation actually stops.
The implementation of panic detection happens at: https://github.com/gem5/gem5/blob/1da285dfcc31b904afc27e440544d006aae25b38/src/arch/arm/linux/system.cc#L73
kernelPanicEvent = addKernelFuncEventOrPanic<Linux::KernelPanicEvent>(
"panic", "Kernel panic in simulated kernel", dmesg_output);
Here we see that the symbol "panic" for the panic() function is the one being tracked.
Related thread: https://stackoverflow.com/questions/56032347/is-there-a-way-to-identify-if-gem5-run-got-over-successfully