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qemu: monitor from gdb

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Ciro Santilli
2018-08-10 16:38:20 +01:00
parent 6ea0b16cd7
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@@ -3627,6 +3627,8 @@ Also asked at https://unix.stackexchange.com/questions/443017/can-i-make-qemu-ex
TODO neither method exits with exit status different from 0, so for now we are just grepping the logs for panic messages, which sucks.
One possibility that gets close would be to use <<gdb>> to break at the `panic` function, and then send a <<qemu-monitor-from-gdb>> `quit` command if that happens, but I don't see a way to exit with non-zero status to indicate error.
gem5 actually detects panics and outputs:
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@@ -3635,7 +3637,7 @@ warn: Kernel panic in simulated kernel
before hanging. gem5 ff52563a214c71fcd1e21e9f00ad839612032e3b `config.ini` has a `system.panic_on_panic` and `system.panic_on_oops` params which I bet will work, but it does not seem to be exposed to `fs.py`, so we don't enable it by default, although we want to.
Detection seems to be symbol based: it parses the kernel image, and trigers when the PC reaches the address of a symbol: https://github.com/gem5/gem5/blob/1da285dfcc31b904afc27e440544d006aae25b38/src/arch/arm/linux/system.cc#L73
Detection seems to be symbol based: it parses the kernel image, and triggers when the PC reaches the address of a symbol: https://github.com/gem5/gem5/blob/1da285dfcc31b904afc27e440544d006aae25b38/src/arch/arm/linux/system.cc#L73
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kernelPanicEvent = addKernelFuncEventOrPanic<Linux::KernelPanicEvent>(
@@ -6942,6 +6944,17 @@ Getting everything to work required careful choice of QEMU command line options:
Peter Maydell said potentially not possible nicely as of August 2018: https://stackoverflow.com/questions/51747744/how-to-run-a-qemu-monitor-command-from-inside-the-guest/51764110#51764110
==== QEMU monitor from GDB
When doing <<gdb-step-debug>> it is possible to send QEMU monitor commands through the GDB `monitor` command, which saves you the trouble of opening yet another shell.
Try for example:
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monitor help
monitor info qtree
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=== Debug the emulator
When you start hacking QEMU or gem5, it is useful to see what is going on inside the emulator themselves.