[Qemu-arm] ARM64 STR Instruction Crash Regression in TCG

[Jason A. Donenfeld]

Hello,

Gcc 7.3 compiles bash's array_flush's dual assignment using:

STP             X20, X20, [X20,#0x10]

But gcc 8.1 compiles it as:

STR             Q0, [X20,#0x10]

Real processors seem okay, and qemu 2.11 seems okay. But qemu 2.12
results in a segfaulting process. I'm pretty sure this is a TCG bug.

In the attached tarball, please find kernel and run.sh. Calling
./run.sh will start the kernel with the bad bash executable that tries
to execute `config=({1..100000})` and crashes. Also included in there
is the actual crashing bash binary, in case you'd like to disassemble
a little bit.

This is affecting builds on https://www.wireguard.com/build-status/ --
as you can see, at the moment aarch64 is failing.

Regards,
Jason

[ attachment: https://data.zx2c4.com/bash-qemu-arm64-crash.tar.xz ]