Link helpers into the linux_kernel_module library

This saves us needing to manually link them in every individual kernel module's Makefile

Author: alex

Cargo.toml

@@ -8,4 +8,5 @@ bitflags = "1"
 
 [build-dependencies]
 bindgen = "*"
+cc = "1.0"
 shlex = "0.1"

build.rs

@@ -1,4 +1,5 @@
 extern crate bindgen;
+extern crate cc;
 extern crate shlex;
 
 use std::env;
@@ -66,4 +67,13 @@ fn main() {
     bindings
         .write_to_file(out_path.join("bindings.rs"))
         .expect("Couldn't write bindings!");
+
+    let mut builder = cc::Build::new();
+    println!("cargo:rerun-if-env-changed=CLANG");
+    builder.compiler(env::var("CLANG").unwrap_or("clang".to_string()));
+    builder.file("src/helpers.c");
+    for arg in shlex::split(&output).unwrap() {
+        builder.flag(&arg);
+    }
+    builder.compile("helpers");
 }

hello-world/Makefile

@@ -1,5 +1,5 @@
 obj-m := helloworld.o
-helloworld-objs := target/x86_64-linux-kernel-module/debug/libhello_world.a ../src/printk_helper.o
+helloworld-objs := target/x86_64-linux-kernel-module/debug/libhello_world.a
 EXTRA_LDFLAGS += --gc-sections --entry=init_module --undefined=cleanup_module
 
 all:

src/printk_helper.c renamed to src/helpers.c

@@ -1,5 +1,5 @@
 obj-m := staticfilesystem.o
-staticfilesystem-objs := target/x86_64-linux-kernel-module/debug/libstatic_filesystem.a ../src/printk_helper.o
+staticfilesystem-objs := target/x86_64-linux-kernel-module/debug/libstatic_filesystem.a
 EXTRA_LDFLAGS += --gc-sections --entry=init_module --undefined=cleanup_module
 
 all: