Linux Kernel Module Cheat

11.1. QEMU user mode getting started

Let’s run userland/c/command_line_arguments.c built with the Buildroot toolchain on QEMU user mode:

./build user-mode-qemu
./run \
  --userland userland/c/command_line_arguments.c \
  --cli-args='asdf "qw er"' \
;

Output:

/path/to/linux-kernel-module-cheat/out/userland/default/x86_64/c/command_line_arguments.out
asdf
qw er

./run --userland path resolution is analogous to that of ./run --baremetal.

./build user-mode-qemu first builds Buildroot, and then runs ./build-userland, which is further documented at: Section 2.8, “Userland setup”. It also builds QEMU. If you ahve already done a QEMU Buildroot setup previously, this will be very fast.

If you modify the userland programs, rebuild simply with:

./build-userland

To rebuild just QEMU userland if you hack it, use:

./build-qemu --mode userland

The:

--mode userland

is needed because QEMU has two separate executables:

qemu-x86_64 for userland
qemu-system-x86_64 for full system

User mode GDB