id = 2146
title = "qemu-system-aarch64 Segfaults"
state = "opened"
created_at = "2024-02-01T19:52:50.052Z"
closed_at = "n/a"
labels = ["host: x86", "target: arm", "workflow::Needs Info"]
url = "https://gitlab.com/qemu-project/qemu/-/issues/2146"
host-os = "Linux Mint 21.3 Cinnamon"
host-arch = "x86_64"
qemu-version = "8.2.50 (v8.2.0-924-gbd2e12310b), 8.2.1, 6.2.0 (Debian 1:6.2+dfsg-2ubuntu6.16)"
guest-os = "Debian GNU/Linux 12"
guest-arch = "aarch64"
description = """Never finishes the script below always segfaults after a few hours
in seemingly random functions."""
reproduce = """This is what i did with qemu version 8.2.1
inside test directory:
1. wget https://download.qemu.org/qemu-8.2.1.tar.xz
2. tar xvJf qemu-8.2.1.tar.xz
3. cd qemu-8.2.1
4. ./configure --target-list="aarch64-linux-user, aarch64-softmmu" --enable-slirp (crashes with and without --enable-debug)
5. make -j$(nproc)
6. ln -sf "$PWD/build/qemu-system-aarch64" "../qemu-system-aarch64"
7. cd ..

Now the VM
1. wget -O installer-linux https://deb.debian.org/debian/dists/bookworm/main/installer-arm64/current/images/netboot/debian-installer/arm64/linux
2. wget -O installer-initrd.gz https://deb.debian.org/debian/dists/bookworm/main/installer-arm64/current/images/netboot/debian-installer/arm64/initrd.gz
3. qemu-img create -f qcow2 hda.qcow2 15G
4. ./qemu-system-aarch64 -M virt -m 6G -cpu cortex-a72 \\
      -kernel installer-linux \\
      -initrd installer-initrd.gz \\
      -drive if=none,file=hda.qcow2,format=qcow2,id=hd \\
      -device virtio-blk-pci,drive=hd \\
      -netdev user,id=mynet \\
      -device virtio-net-pci,netdev=mynet \\
      -nographic -no-reboot \\
      -accel tcg,thread=multi \\
      -smp 8
5. Install minimal debian inside the VM
6. sudo virt-copy-out -a hda.qcow2 /boot/vmlinuz-6.1.0-17-arm64 /boot/initrd.img-6.1.0-17-arm64 .
7. ./qemu-system-aarch64 -M virt -m 6G -cpu cortex-a72 \\
      -kernel vmlinuz-6.1.0-17-arm64 \\
      -initrd initrd.img-6.1.0-17-arm64 \\
      -append 'root=/dev/vda2' \\
      -drive if=none,file=hda.qcow2,format=qcow2,id=hd \\
      -device virtio-blk-pci,drive=hd \\
      -netdev user,id=mynet,hostfwd=tcp::10022-:22 \\
      -device virtio-net-pci,netdev=mynet \\
      -nographic \\
      -accel tcg,thread=multi \\
      -smp 8
8. Now run this script inside some directory inside the VM(you might need to install gcc first)

#!/bin/bash

wget --no-clobber https://sourceware.org/pub/binutils/releases/binutils-2.41.tar.xz   
wget --no-clobber https://ftp.gnu.org/gnu/mpfr/mpfr-4.2.0.tar.xz   
wget --no-clobber https://ftp.gnu.org/gnu/gmp/gmp-6.3.0.tar.xz    
wget --no-clobber https://ftp.gnu.org/gnu/mpc/mpc-1.3.1.tar.gz    
wget --no-clobber https://ftp.gnu.org/gnu/gcc/gcc-13.2.0/gcc-13.2.0.tar.xz   

BUG_TARGET="$(uname -m)-bug-linux-gnu"

tar -xf binutils-2.41.tar.xz   
cd binutils-2.41   
mkdir -vp build   
cd build   
../configure --prefix=$PWD        \\
             --with-sysroot=$PWD  \\
             --target=$BUG_TARGET \\
             --disable-nls        \\
             --enable-gprofng=no  \\
             --disable-werror     \\
             --disable-gdb
make --jobs $(nproc)   
cd ../..   
rm -rf binutils   

tar -xf gcc-13.2.0.tar.xz   
cd gcc-13.2.0   
tar -xf ../mpfr-4.2.0.tar.xz   
tar -xf ../gmp-6.3.0.tar.xz   
tar -xf ../mpc-1.3.1.tar.gz   
mv mpfr-4.2.0 mpfr   
mv gmp-6.3.0 gmp   
mv mpc-1.3.1 mpc   
mkdir -vp build   
cd build   
../configure --prefix=$PWD             \\
             --with-sysroot=$PWD       \\
             --target=$BUG_TARGET      \\
             --with-glibc-version=2.38 \\
             --with-newlib             \\
             --without-headers         \\
             --enable-default-pie      \\
             --enable-default-ssp      \\
             --disable-nls             \\
             --disable-shared          \\
             --disable-multilib        \\
             --disable-threads         \\
             --disable-libatomic       \\
             --disable-libgomp         \\
             --disable-libquadmath     \\
             --disable-libssp          \\
             --disable-libvtv          \\
             --disable-libstdcxx       \\
             --enable-languages=c,c++
make --jobs $(nproc)   
cd ../..   
rm -rf gcc"""
additional = """I tried all the versions listed above, 6.2 usually segfaults in binutils while the other two run further.

Example:
```
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x000055555615dd37 in tlb_index (cpu=<Cannot access memory at address 0x7fffefffe1c8>,
    mmu_idx=<Cannot access memory at address 0x7fffefffe1c0>,
    addr=<Cannot access memory at address 0x7fffefffe1b8>)
    at qemu-8.2.1/include/exec/cpu_ldst.h:367
367\t    uintptr_t size_mask = cpu->neg.tlb.f[mmu_idx].mask >> CPU_TLB_ENTRY_BITS;
[Current thread is 1 (LWP 857562)]
```"""