Re: tst-arm-mte bug: PSTATE.TCO is cleared on exceptions

[Szabolcs Nagy]

The 05/07/2020 10:21, Richard Henderson wrote:
> A reproducer would be most helpful.
> 
> Something that can help is saving a VM snapshot with the kernel booted and the
> user logged in, just ready to run the test program.  Then you can get back to
> exactly the state you want before things go wrong, even with a different qemu
> build.

i got some time to create a reproducer (with public code),
temporarily hosting the binaries at

http://port70.net/~nsz/tmp/qemu-bug.tar.gz
~251M

here

echo ./bug.sh | ./qemu-bug.sh

crashes in about 1 minute (where qemu-bug.sh
loads a snapshot with root shell and ./bug.sh
triggers the bug)

the disk rootfs is based on
https://distfiles.adelielinux.org/adelie/1.0/iso/rc1/adelie-rootfs-aarch64-1.0-rc1-20200206.txz
the kernel Image is linux mte-v3 with reverting the commit
"arm64: mte: Check the DT memory nodes for MTE support"
qemu is static linked from the branch tgt-arm-mte.

the userspace workload that triggers the bug is using the
adelie linux package manager with a malloc with tagging.
(the malloc implementation is a modified version of
https://github.com/richfelker/mallocng-draft
the code is on the disk image, it has known issues, but
it should not crash qemu)

i will remove the file after a few days. hope this helps.