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qemu: exit on panic by default instead of hanging

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Ciro Santilli
2018-08-10 08:51:49 +01:00
parent faec16e00c
commit 13e0ea7801
2 changed files with 30 additions and 17 deletions
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README.adoc
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@@ -3516,16 +3516,6 @@ When a panic happens, <<linux-kernel-magic-keys,`Shift-PgUp`>> does not work as
On panic, the kernel dies, and so does our terminal.
Make the kernel reboot after n seconds after panic:
....
echo 1 > /proc/sys/kernel/panic
....
Can also be controlled with the `panic=` kernel boot parameter.
`0` to disable: https://unix.stackexchange.com/questions/29567/how-to-configure-the-linux-kernel-to-reboot-on-panic/29569#29569
The panic trace looks like:
....
@@ -3616,17 +3606,37 @@ Related:
Basically just calls `panic("BUG!")` for most archs.
===== Shutdown VM on panic
===== Exit emulator on panic
Useful to automate bisections.
For testing purposes, it is very useful to quit the emulator automatically in case of kernel panic, instead of just hanging forever.
QEMU:
In QEMU, we enable it by default with:
* `panic=-1` command line option which reboots the kernel immediately on panic, see: <<reboot-on-panic>>
* QEMU `-no-reboot`, which makes QEMU exit when the guest tries to reboot
Also asked at https://unix.stackexchange.com/questions/443017/can-i-make-qemu-exit-with-failure-on-kernel-panic which also mentions the x86_64 `-device pvpanic`, but I don't see much advantage to it.
TODO neither method exits with exit status different from 0, so the only thing I can do for now is to grep the logs, which sucks.
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.
===== Reboot on panic
Make the kernel reboot after n seconds after panic:
....
./run -E 'insmod /panic.ko' -e 'panic=1' -- -no-reboot
echo 1 > /proc/sys/kernel/panic
....
gem5: TODO gem5's `config.ini` has a `system.panic_on_panic` param which I bet will work, but it does not seem to be exposed to `fs.py`.
Can also be controlled with the `panic=` kernel boot parameter.
`0` to disable, `-1` to reboot immediately.
Bibliography:
* https://github.com/torvalds/linux/blob/v4.17/Documentation/admin-guide/kernel-parameters.txt#L2931
* https://unix.stackexchange.com/questions/29567/how-to-configure-the-linux-kernel-to-reboot-on-panic/29569#29569
===== Panic trace show addresses instead of symbols
@@ -5411,7 +5421,7 @@ sendkey shift-pgdown
===== Ctrl Alt Del
Reboot guest:
Run `/sbin/reboot` on guest:
....
Ctrl-Alt-Del
@@ -5423,6 +5433,8 @@ Enabled from our link:rootfs_overlay/etc/inittab[]:
::ctrlaltdel:/sbin/reboot
....
Linux tries to reboot, and QEMU shutdowns due to the `-no-reboot` option which we set by default for: <<exit-emulator-on-panic>>.
Under the hood, behaviour is controlled by the `reboot` syscall:
....