Tools for building and testing for Cortex-M with Bazel

gif

building

An elf can be built for a target platform by specifying the platform

bazel build \
  --platforms=@cortex_m//platform:lm3s6965evb \
  <binary>

where <binary> is a cc_binary target.

Supported platforms provide generic startup code associated with the default registered toolchain.

running with qemu

An elf can be run with qemu-system-arm. This requires an installation of nix to download the qemu package.

bazel run \
  --run_under=@cortex_m//:qemu_runner \
  --platforms=@cortex_m//platform:lm3s6965evb \
  <binary> -- <qemu-args>

By default, the QEMU runner sets the machine to match the target platform. Additional arguments can be passed to qemu-system-arm after -- (e.g., the GDB connection or to freeze CPU at startup).

enabling semihosting

By default, semihosting is not enabled when building targets. It can be enabled with bool flag --@cortex_m//config:semihosting.

bazel run \
  --run_under=@cortex_m//:qemu_runner \
  --platforms=@cortex_m//platform:lm3s6965evb \
  --@cortex_m//config:semihosting \
  <binary>

running tests with qemu

cc_test targets can be built for the target platform and run under emulation with a CcTestRunner that uses qemu-system-arm. This runner is registered by default. Note that --@cortex_m//config:semihosting must be passed so that elf is built with semihosting enabled.

bazel test \
  --platforms=@cortex_m//platform:lm3s6965evb \
  --@cortex_m//config:semihosting \
  //...

flagless builds

transition_config_binary and transition_config_test can be used to transition a binary target to always enable or disable semihosting, set the target platform, and specify extra toolchains.

load(
    "@cortex_m//rules:transitions.bzl",
    "transition_config_binary",
    "transition_config_test",
)

transition_config_binary(
    name = "binary",
    src = ":_binary",
    semihosting = "enabled",
    platform = "@cortex_m//platform:lm3s6965evb",
)

transition_config_test(
    name = "test",
    src = ":_test",
    platform = "@cortex_m//platform:lm3s6965evb",
)