Remove libbpf as a submodule

Instead clone the libbpf repo at a specific hash during setup.
This is to fix an issue whereby submodules are not included
in the tarball and therefore won't be updated/fetched during
setup after unzipping the tarball.

.github/workflows/build-scheds.yml

@@ -36,11 +36,6 @@ jobs:
 
       - uses: actions/checkout@v4
 
-      # libbpf
-      - run: git clone --recurse-submodules --branch v1.3.0 https://github.com/libbpf/libbpf.git
-      - run: make -j -C libbpf/src
-      - run: sudo make -j -C libbpf/src install
-
       # meson
       - run: pip install meson
 
@@ -61,7 +56,7 @@ jobs:
       ### END DEPENDENCIES ###
 
       # The actual build:
-      - run: meson setup build -Dlibbpf_a=`pwd`/libbpf/src/libbpf.a -Dkernel=$(pwd)/linux
+      - run: meson setup build -Dkernel=$(pwd)/linux
       - run: meson compile -C build
 
       # Print CPU model before running the tests (this can be useful for

.gitignore

@@ -0,0 +1 @@
+libbpf/

.gitmodules

@@ -1,3 +0,0 @@
-[submodule "libbpf"]
-	path = libbpf
-	url = https://github.com/libbpf/libbpf

README.md

@@ -198,7 +198,7 @@ repo](https://mesonbuild.com/Quick-guide.html#installation-from-source) and call
   standard utilities including `awk`.
 - `clang`: >=16 required, >=17 recommended
 - `libbpf`: >=1.2.2 required, >=1.3 recommended (`RESIZE_ARRAY` support is
-  new in 1.3). It's preferred to link statically against the source from the libbpf git submodule.
+  new in 1.3). It's preferred to link statically against the source from the libbpf git repo, which is cloned during setup.
 - Rust toolchain: >=1.72
 - `libelf`, `libz`, `libzstd` if linking against staic `libbpf.a`
 - `bpftool` (usually available in `linux-tools-common`)
@@ -210,7 +210,7 @@ repo](https://mesonbuild.com/Quick-guide.html#installation-from-source) and call
 commands in the root of the tree builds and installs all schedulers under
 `~/bin`.
 
-#### Static linking against libbpf submodule (preferred)
+#### Static linking against libbpf (preferred)
 
  ```
 $ cd $SCX
@@ -219,7 +219,7 @@ $ meson compile -C build
 $ meson install -C build
 ```
 
-Note: `meson setup` will also fetch the libbpf submodule and `meson compile` will build it.
+Note: `meson setup` will also clone the libbpf repo and `meson compile` will build it.
 
 #### Dynamic linking against libbpf
 ```

libbpf

@@ -1 +0,0 @@
-Subproject commit 20c0a9e3d7e7d4aeb283eae982543c9cacc29477

meson-scripts/build_libbpf

@@ -23,5 +23,5 @@ for arg in ${args[@]:(idx+1)}; do
     esac
 done
 
-make_out=$(env CC="$cc" CFLAGS="$cflags" BUILD_STATIC_ONLY=y "$2" -C "$3" -j"$4")
+make_out=$(env CC="$cc" CFLAGS="$cflags" BUILD_STATIC_ONLY=y DESTDIR=. "$2" install -C "$3" -j"$4")
 exit $?

meson-scripts/fetch_libbpf

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+cd $1
+rm -rf libbpf
+git clone --depth=1 https://github.com/libbpf/libbpf
+cd libbpf
+git fetch --depth=1 origin $2
+git checkout $2
+
+# This is needed because we haven't built libbpf yet
+# and this is where the headers will end up
+mkdir src/usr
+mkdir src/usr/include

meson.build

@@ -28,6 +28,8 @@ get_sys_incls = find_program(join_paths(meson.current_source_dir(),
                                         'meson-scripts/get_sys_incls'))
 test_sched  = find_program(join_paths(meson.current_source_dir(),
                                       'meson-scripts/test_sched'))
+fetch_libbpf = find_program(join_paths(meson.current_source_dir(),
+                                      'meson-scripts/fetch_libbpf'))
 build_libbpf = find_program(join_paths(meson.current_source_dir(),
                                       'meson-scripts/build_libbpf'))
 if enable_rust
@@ -46,9 +48,11 @@ elif bpf_clang_maj < 17
           .format(bpf_clang.full_path(), bpf_clang_ver))
 endif
 
-libbpf_path = '@0@/libbpf/src'.format(meson.current_source_dir())
+libbpf_path = '@0@/libbpf/src'.format(meson.current_build_dir())
 libbpf_a = '@0@/libbpf.a'.format(libbpf_path)
 should_build_libbpf = true
+libbpf_h = get_option('libbpf_h')
+libbpf_local_h = get_option('libbpf_h')
 
 if get_option('libbpf_a') == 'disabled'
   libbpf_a = ''
@@ -74,10 +78,12 @@ if should_build_libbpf
     error('To build the libbpf library "make" and "jq" are required')
   endif
 
-  message('Updating libbpf submodule')
-  run_command('git', 'submodule', 'update', '--init', '--recursive', check: true)
-  # make sure it's clean
-  run_command('git', 'submodule', 'foreach', '--recursive', 'git', 'clean', '-xfd', check: true)
+  libbpf_h = ['@0@/usr/include'.format(libbpf_path)]
+  libbpf_local_h = ['.@0@/libbpf/src/usr/include'.format(meson.current_build_dir().replace(meson.current_source_dir(), ''))]
+
+  message('Fetching libbpf repo')
+  libbpf_commit = '4f875865b772c4f534bc0a665bbd988193825bd4'
+  run_command(fetch_libbpf, meson.current_build_dir(), libbpf_commit, check: true)
 
   # setup the build target
   executable('cc_cflags_probe', 'meson-scripts/cc_cflags_probe.c', install: false, pie: true)
@@ -104,7 +110,7 @@ endif
 if libbpf_a != ''
   libbpf_dep = [declare_dependency(
     link_args: libbpf_a,
-    include_directories: get_option('libbpf_h')),
+    include_directories: libbpf_local_h),
     cc.find_library('elf'),
     cc.find_library('z'),
     cc.find_library('zstd')]
@@ -156,7 +162,7 @@ message('cpu=@0@ bpf_base_cflags=@1@'.format(cpu, bpf_base_cflags))
 libbpf_c_headers = []
 
 if libbpf_a != ''
-  foreach header: get_option('libbpf_h')
+  foreach header: libbpf_h
     libbpf_c_headers += ['-I', header]
   endforeach
 endif
@@ -194,7 +200,7 @@ foreach flag: bpf_base_cflags
 endforeach
 
 if libbpf_a != ''
-  foreach header: get_option('libbpf_h')
+  foreach header: libbpf_h
     cargo_env.append('BPF_EXTRA_CFLAGS_PRE_INCL', '-I' + header, separator: ' ')
   endforeach