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Building QEMU

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Yuriy Kolerov edited this page Jul 27, 2023 · 13 revisions

Building QEMU

Install all necessary prerequisites which are necessary for building QEMU: https://wiki.qemu.org/Hosts/Linux. Then prepare sources and a build directory:

git clone https://github.com/foss-for-synopsys-dwc-arc-processors/qemu
mkdir -p qemu/build
cd qemu/build

Configure QEMU (use your own --prefix value):

../configure --target-list=arc-softmmu,arc64-softmmu,arc-linux-user,arc64-linux-user \
             --enable-debug --enable-debug-tcg --prefix=/tools/qemu

Build an install:

make
make install

Configure your environment:

export QEMU_HOME="/tools/qemu"
export PATH="${QEMU_HOME}/bin:$PATH"

(From https://github.com/foss-for-synopsys-dwc-arc-processors/qemu/wiki/Building-QEMU-for-ARC, https://github.com/foss-for-synopsys-dwc-arc-processors/qemu/wiki/QEMU-and-Zephyr, https://github.com/foss-for-synopsys-dwc-arc-processors/qemu/wiki/QEMU-traces, https://github.com/foss-for-synopsys-dwc-arc-processors/qemu/wiki/Tips-and-Tricks-for-Troubleshooting)

Prerequisites

ℹ️ Refer to the official documentation for details.

Install necessary packages for Arch:

sudo pacman -S git cmake ninja gperf ccache dfu-util dtc wget            \
               python-pip python-setuptools python-wheel xz file make

Install necessary packages for Fedora:

sudo dnf group install "Development Tools" "C Development Tools and Libraries"
dnf install git cmake ninja-build gperf ccache dfu-util dtc wget         \
            python3-pip xz file glibc-devel.i686 libstdc++-devel.i686

Install necessary packages for Ubuntu:

sudo apt-get install --no-install-recommends git cmake ninja-build gperf \
                     ccache dfu-util device-tree-compiler wget           \
                     python3-pip python3-setuptools python3-wheel        \
                     xz-utils file make gcc gcc-multilib

Install necessary packages for Void:

sudo xbps-install git cmake ninja gperf ccache dfu-util dtc wget  \
                  python3-pip python3-setuptools python3-wheel xz \
                  file make

Setup

Then prepare sources and a build directory:

git clone https://github.com/foss-for-synopsys-dwc-arc-processors/qemu
mkdir -p qemu/build
cd qemu/build

Configure QEMU inside of the build directory (use your own --prefix value for installation path):

../configure --target-list=arc-softmmu,arc64-softmmu,arc-linux-user,arc64-linux-user \
             --prefix=/tools/qemu --enable-debug --enable-debug-tcg --enable-trace-backends=simple \
             --disable-plugins --skip-meson --disable-werror --disable-pie --enable-trace-backends=simple

What options are responsible for what:

  • --target-list=arc-softmmu,arc64-softmmu,arc-linux-user,arc64-linux-user — build QEMU both for these targets:
    • qemu-system-arc — system emulation for ARC HS3x/4x/5x processors family;
    • qemu-system-arc64 — system emulation for ARC HS6x processors family;
    • qemu-arc — user space Linux emulation for ARC HS3x/4x/5x processors family;
    • qemu-arc64 — user space Linux emulation for ARC HS6x processors family.
  • --prefix=/tools/qemu — an installation path.
  • --enable-debug --enable-debug-tcg --enable-trace-backends=simple --disable-plugins — options for development needs.
  • --enable-trace-backends=simple — for tracing (described in Profiling with QEMU).
  • --skip-meson — do not run Meson on every build.
  • --disable-werror — in case QEMU emits unexpected warnings.
  • --disable-pie — needed for older GCC (like in CentOS 7).

To enable TCG testing, the arc-elf32-gcc and arc64-elf-gcc compilers must be available during configuration, and the following two arguments added to the command above

--cross-cc-arc=arc-elf32-gcc --cross-cc-arc64=arc64-elf-gcc

Build and install

make
make install

Debugging

QEMU provides several tools to debug both itself and the binary being executed.

Debugging using GDB

QEMU has a GDBstub with which it allows an external GDB instance to connect directly to the running executable. See more information about this in here.

If you require full system emulation, the GLibC tests show how to launch these and debug the running executable without having to the debug the whole kernel.

Debugging using QEMU

Sometimes it is useful to get more information from the simulator than the one GDB has access to. There are a few ways to obtain more information.

Enhanced logging

To enable logging, it is necessary to provide the enabled log levels with the -d flag. Some of the more relevant ones are:

in_asm          show target assembly code for each compiled TB
nochain         do not chain compiled TBs so that "exec" and "cpu" show complete traces
exec            show trace before each executed TB (lots of logs)
cpu             show CPU registers before entering a TB (lots of logs)
fpu             include FPU registers in the 'cpu' logging
int             show interrupts/exceptions in short format
mmu             log MMU-related activities
unimp           log unimplemented functionality

To get a complete listing, run qemu-system-arc -d help Use -D <logfile> to dump the logs into a file instead of stdout.

Tracing

QEMU provides a tracing infrastructure which may help in debugging or analyzing what happens within a simulation cycle. At this moment, there are two tracers added into ARC backend, one for MMU operations, and the other for exceptions:

# mmu.c
mmu_command(uint32_t address, const char *command, uint32_t pd0, uint32_t pd1) "[MMU] at 0x%08x, CMD=%s, PD0=0x%08x, PD1=0x%08x"

# helper.c
excp_info(uint32_t address, const char *name) "[IRQ] at 0x08, Exception=%s"

To run this tracing:

  1. Build with the --enable-trace-backends=simple configure parameter:
  2. Create a file with the events you want to trace. For example:
$ cat > events.trc << 'EOF'
mmu_command
excp_info
EOF
  1. Run the virtual machine to produce a trace file:
qemu-system-arc --trace events=events.trc ... # your normal QEMU invocation
  1. Pretty-print the binary trace file:
$QEMU_SRC/scripts/simpletrace.py $QEMU_SRC/target/arc/trace-events trace-* # Override * with QEMU <pid>

Testing

Testing using QEMU as the simulator can be done in multiple ways. The currently configured testsuits are:

In general, the most transparent way is by using usermode emulation with binfmt for seamless execution. This is what is used in some of the GLibC tests mentioned above.

TCG tests

TCG is the internal language that powers QEMU.

There are some assembly tests that validate the basic function of several instructions in QEMU.

To run these, make sure that the compilers specified in '--cross-cc-arc' and '--cross-cc-arc64' are available during build time and when running the commands below:

make clean-tcg
make build-tcg
make check-tcg
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