build: Install musl-based toolchains in the docker.

Author: guyush1

Dockerfile

@@ -1,7 +1,8 @@
 FROM ubuntu:24.04
 
-# Install dependencies
-RUN apt update && apt install -y \
+RUN apt update
+
+RUN apt install -y \
     bison \
     file \
     flex \
@@ -18,16 +19,26 @@ RUN apt update && apt install -y \
     gcc-mipsel-linux-gnu \
     gcc-powerpc-linux-gnu \
     git \
-    libncurses-dev \
     libtool \
     m4  \
     make \
     patch \
     pkg-config \
     python3.12 \
+    python3-pip \
     libpython3-dev \
     texinfo \
     wget \
     xz-utils
 
+# Remove externally-managed constrainsts since we run inside a docker...
+RUN rm -f /usr/lib/python3.*/EXTERNALLY-MANAGED
+RUN python3.12 -m pip install requests
+
+COPY src/docker_utils/download_musl_toolchains.py .
+RUN python3.12 -u download_musl_toolchains.py
+
 WORKDIR /app/gdb
+
+ENTRYPOINT ["/entrypoint.sh"]
+CMD ["bash"]

Makefile

@@ -27,7 +27,7 @@ help:
 	@echo ""
 	@echo "  make clean"
 
-build/build-docker-image.stamp: Dockerfile
+build/build-docker-image.stamp: Dockerfile src/docker_utils/download_musl_toolchains.py
 	mkdir -p build
 	docker buildx build --tag gdb-static .
 	touch build/build-docker-image.stamp

src/docker_utils/download_musl_toolchains.py

@@ -0,0 +1,80 @@
+#!/usr/bin/env python3.12
+
+import requests
+import tarfile
+import os
+import shutil
+
+from pathlib import Path
+
+ARCHS = {
+    "x86_64" : "https://musl.cc/x86_64-linux-musl-cross.tgz",
+    "arm" : "https://musl.cc/arm-linux-musleabi-cross.tgz",
+    "aarch64" : "https://musl.cc/aarch64-linux-musl-cross.tgz",
+    "powerpc" : "https://musl.cc/powerpc-linux-musl-cross.tgz",
+    "mips" : "https://musl.cc/mips-linux-musl-cross.tgz",
+    "mipsel" : "https://musl.cc/mipsel-linux-musl-cross.tgz",
+}
+CHUNK_SIZE = 65536
+MUSL_TOOLCHAINS_DIR = Path("/musl-toolchains")
+ENTRYPOINT = "/entrypoint.sh"
+
+def download_file(url: str, filename: str):
+    print(f"Downloading {filename}")
+    with requests.get(url, stream=True) as r:
+        r.raise_for_status()
+        with open(filename, "wb") as f:
+            for chunk in r.iter_content(chunk_size=CHUNK_SIZE):
+                f.write(chunk)
+    print(f"{filename} downloaded.")
+
+def extract_tarball(filename: str, dst: Path):
+    print(f"Extracting {filename}")
+    with tarfile.open(filename, "r:gz") as tar:
+        tar.extractall(path=dst)
+    print(f"{filename} extracted")
+
+def add_to_path(curr_path: str, package_path: Path):
+    return curr_path + ":" + str((package_path / "bin").resolve())
+
+
+def main():
+    os.mkdir(MUSL_TOOLCHAINS_DIR)
+
+    updated_path = "$PATH"
+    for arch, url in ARCHS.items():
+        filename = url.split("/")[-1]
+        download_file(url, filename)
+        extract_tarball(filename, MUSL_TOOLCHAINS_DIR)
+        updated_path = add_to_path(updated_path, MUSL_TOOLCHAINS_DIR / filename.removesuffix(".tgz"))
+
+    # Fix the x86_64 dynamic loader if needed:
+    # Unfortunately, the internal gdb build scripts builds some binaries (that generate documentation)
+    # in a dynamic manner.
+    #
+    # Because we may use a musl-based toolchain, this means that we need to set-up the dynamic loader.
+    # The fix may seem a little hacky, but it is simple, and is the best we can do.
+    if "x86_64" in ARCHS:
+        x86_toolchain_name = ARCHS["x86_64"].split("/")[-1].removesuffix(".tgz")
+        x86_toolchain_path = MUSL_TOOLCHAINS_DIR / x86_toolchain_name
+        x86_loader_path = x86_toolchain_path / "x86_64-linux-musl" / "lib" / "libc.so"
+        shutil.copy2(x86_loader_path, "/lib/ld-musl-x86_64.so.1")
+
+    # Create the entrypoint with the updated path.
+    with open(ENTRYPOINT, mode="w") as f:
+        f.write(
+f"""#!/usr/bin/env bash
+export PATH="{updated_path}"
+exec "$@"
+""")
+
+    # Make sure we can execute the entrypoint.
+    os.chmod(ENTRYPOINT, 0o755)
+
+    # Append the path to bash.bashrc so that other users will have these paths.
+    with open("/etc/bash.bashrc", mode="a") as f:
+        f.write(f"\nexport PATH=\"{updated_path}\"")
+
+
+if __name__ == "__main__":
+    main()