libbpf: make RINGBUF map size adjustments more eagerly

.github/actions/vmtest/action.yml

@@ -0,0 +1,39 @@
+name: 'vmtest'
+description: 'Build + run vmtest'
+inputs:
+  arch:
+    description: 'what arch to test'
+    required: true
+    default: 'x86_64'
+  toolchain:
+    description: 'what toolchain to use'
+    required: true
+    default: 'gcc'
+runs:
+  using: "composite"
+  steps:
+    # 1. Setup environment
+    - name: Setup build environment
+      uses: libbpf/ci/setup-build-env@master
+    # 2. Build
+    - name: Build kernel image
+      shell: bash
+      run: ${GITHUB_ACTION_PATH}/build.sh ${{ inputs.arch }} ${{ inputs.toolchain }}
+    - name: Build selftests
+      shell: bash
+      run: ${GITHUB_ACTION_PATH}/build_selftests.sh ${{ inputs.toolchain }}
+      env:
+        VMLINUX_BTF: ${{ github.workspace }}/vmlinux
+    # 3. Test
+    - name: Prepare rootfs
+      uses: libbpf/ci/prepare-rootfs@master
+      with:
+        project-name: 'libbpf'
+        arch: ${{ inputs.arch }}
+        kernel-root: '.'
+    - name: Run selftests
+      uses: libbpf/ci/run-qemu@master
+      with:
+        arch: ${{ inputs.arch}}
+        img: '/tmp/root.img'
+        vmlinuz: '${{ github.workspace }}/vmlinuz'

.github/actions/vmtest/build.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+set -euo pipefail
+
+ARCH="$1"
+TOOLCHAIN="$2"
+TOOLCHAIN_NAME="$(echo $TOOLCHAIN | cut -d '-' -f 1)"
+TOOLCHAIN_VERSION="$(echo $TOOLCHAIN | cut -d '-' -f 2)"
+
+if [ "$TOOLCHAIN_NAME" == "llvm" ]; then
+export LLVM="-$TOOLCHAIN_VERSION"
+fi
+
+THISDIR="$(cd $(dirname $0) && pwd)"
+
+source "${THISDIR}"/helpers.sh
+
+travis_fold start build_kernel "Building kernel with $TOOLCHAIN"
+
+cp ${GITHUB_WORKSPACE}/travis-ci/vmtest/configs/config-latest.${ARCH} .config
+
+make -j $((4*$(nproc))) olddefconfig all > /dev/null
+
+travis_fold end build_kernel

.github/actions/vmtest/build_selftests.sh

@@ -0,0 +1,52 @@
+#!/bin/bash
+
+set -euo pipefail
+
+THISDIR="$(cd $(dirname $0) && pwd)"
+
+source "${THISDIR}"/helpers.sh
+
+TOOLCHAIN="$1"
+TOOLCHAIN_NAME="$(echo $TOOLCHAIN | cut -d '-' -f 1)"
+TOOLCHAIN_VERSION="$(echo $TOOLCHAIN | cut -d '-' -f 2)"
+
+if [ "$TOOLCHAIN_NAME" == "llvm" ]; then
+export LLVM="-$TOOLCHAIN_VERSION"
+LLVM_VER=$TOOLCHAIN_VERSION
+else
+LLVM_VER=15
+fi
+
+travis_fold start prepare_selftests "Building selftests with $TOOLCHAIN"
+
+LIBBPF_PATH="${REPO_ROOT}"
+
+PREPARE_SELFTESTS_SCRIPT=${THISDIR}/prepare_selftests-${KERNEL}.sh
+if [ -f "${PREPARE_SELFTESTS_SCRIPT}" ]; then
+	(cd "${REPO_ROOT}/${REPO_PATH}/tools/testing/selftests/bpf" && ${PREPARE_SELFTESTS_SCRIPT})
+fi
+
+if [[ "${KERNEL}" = 'LATEST' ]]; then
+	VMLINUX_H=
+else
+	VMLINUX_H=${THISDIR}/vmlinux.h
+fi
+
+cd ${REPO_ROOT}/${REPO_PATH}
+make \
+	CLANG=clang-${LLVM_VER} \
+	LLC=llc-${LLVM_VER} \
+	LLVM_STRIP=llvm-strip-${LLVM_VER} \
+	VMLINUX_BTF="${VMLINUX_BTF}" \
+	VMLINUX_H="${VMLINUX_H}" \
+	-C "${REPO_ROOT}/${REPO_PATH}/tools/testing/selftests/bpf" \
+	-j $((4*$(nproc))) > /dev/null
+cd -
+mkdir "${LIBBPF_PATH}"/selftests
+cp -R "${REPO_ROOT}/${REPO_PATH}/tools/testing/selftests/bpf" \
+	"${LIBBPF_PATH}"/selftests
+cd "${LIBBPF_PATH}"
+rm selftests/bpf/.gitignore
+git add selftests
+
+travis_fold end prepare_selftests

.github/actions/vmtest/helpers.sh

@@ -0,0 +1,44 @@
+# $1 - start or end
+# $2 - fold identifier, no spaces
+# $3 - fold section description
+travis_fold() {
+  local YELLOW='\033[1;33m'
+  local NOCOLOR='\033[0m'
+  if [ -z ${GITHUB_WORKFLOW+x} ]; then
+    echo travis_fold:$1:$2
+    if [ ! -z "${3:-}" ]; then
+      echo -e "${YELLOW}$3${NOCOLOR}"
+    fi
+    echo
+  else
+    if [ $1 = "start" ]; then
+      line="::group::$2"
+      if [ ! -z "${3:-}" ]; then
+        line="$line - ${YELLOW}$3${NOCOLOR}"
+      fi
+    else
+      line="::endgroup::"
+    fi
+    echo -e "$line"
+  fi
+}
+
+__print() {
+  local TITLE=""
+  if [[ -n $2 ]]; then
+      TITLE=" title=$2"
+  fi
+  echo "::$1${TITLE}::$3"
+}
+
+# $1 - title
+# $2 - message
+print_error() {
+  __print error $1 $2
+}
+
+# $1 - title
+# $2 - message
+print_notice() {
+  __print notice $1 $2
+}

.github/workflows/test.yml

@@ -0,0 +1,57 @@
+name: bpf-ci
+
+on:
+  pull_request:
+
+concurrency: 
+  group: ci-test-${{ github.head_ref }}
+  cancel-in-progress: true
+
+jobs:
+  VM_Test:
+    runs-on: ${{ matrix.runs_on }}
+    name: Kernel ${{ matrix.kernel }} on ${{ matrix.runs_on }} with ${{ matrix.toolchain }}
+    timeout-minutes: 100
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - kernel: 'LATEST'
+            runs_on: ubuntu-latest
+            arch: 'x86_64'
+            toolchain: 'gcc'
+          - kernel: 'LATEST'
+            runs_on: ubuntu-latest
+            arch: 'x86_64'
+            toolchain: 'llvm-15'
+          - kernel: 'LATEST'
+            runs_on: z15
+            arch: 's390x'
+            toolchain: 'gcc'
+    env:
+      AUTHOR_EMAIL: "$(git log -1 --pretty=\"%aE\")"
+      KERNEL: LATEST
+      REPO_ROOT: ${{ github.workspace }}
+      REPO_PATH: ""
+    steps:
+      - uses: actions/checkout@v2
+      - if: ${{ github.repository == 'kernel-patches/vmtest' }}
+        name: Download bpf-next tree
+        uses: libbpf/ci/get-linux-source@master
+        with:
+          dest: '.kernel'
+      - if: ${{ github.repository == 'kernel-patches/vmtest' }}
+        name: Move linux source in place
+        shell: bash
+        run: |
+          rm -rf .kernel/.git
+          cp -rf .kernel/. .
+          rm -rf .kernel
+      - uses: libbpf/ci/patch-kernel@master
+        with:
+          patches-root: '${{ github.workspace }}/travis-ci/diffs'
+          repo-root: '${{ github.workspace }}'
+      - uses: ./.github/actions/vmtest
+        with:
+          arch: ${{ matrix.arch }}
+          toolchain: ${{ matrix.toolchain }}

README

@@ -1,18 +0,0 @@
-Linux kernel
-============
-
-There are several guides for kernel developers and users. These guides can
-be rendered in a number of formats, like HTML and PDF. Please read
-Documentation/admin-guide/README.rst first.
-
-In order to build the documentation, use ``make htmldocs`` or
-``make pdfdocs``.  The formatted documentation can also be read online at:
-
-    https://www.kernel.org/doc/html/latest/
-
-There are various text files in the Documentation/ subdirectory,
-several of them using the Restructured Text markup notation.
-
-Please read the Documentation/process/changes.rst file, as it contains the
-requirements for building and running the kernel, and information about
-the problems which may result by upgrading your kernel.

tools/lib/bpf/libbpf.c

@@ -2331,6 +2331,37 @@ int parse_btf_map_def(const char *map_name, struct btf *btf,
 	return 0;
 }
 
+static size_t adjust_ringbuf_sz(size_t sz)
+{
+	__u32 page_sz = sysconf(_SC_PAGE_SIZE);
+	__u32 mul;
+
+	/* if user forgot to set any size, make sure they see error */
+	if (sz == 0)
+		return 0;
+	/* Kernel expects BPF_MAP_TYPE_RINGBUF's max_entries to be
+	 * a power-of-2 multiple of kernel's page size. If user diligently
+	 * satisified these conditions, pass the size through.
+	 */
+	if ((sz % page_sz) == 0 && is_pow_of_2(sz / page_sz))
+		return sz;
+
+	/* Otherwise find closest (page_sz * power_of_2) product bigger than
+	 * user-set size to satisfy both user size request and kernel
+	 * requirements and substitute correct max_entries for map creation.
+	 */
+	for (mul = 1; mul <= UINT_MAX / page_sz; mul <<= 1) {
+		if (mul * page_sz > sz)
+			return mul * page_sz;
+	}
+
+	/* if it's impossible to satisfy the conditions (i.e., user size is
+	 * very close to UINT_MAX but is not a power-of-2 multiple of
+	 * page_size) then just return original size and let kernel reject it
+	 */
+	return sz;
+}
+
 static void fill_map_from_def(struct bpf_map *map, const struct btf_map_def *def)
 {
 	map->def.type = def->map_type;
@@ -2344,6 +2375,10 @@ static void fill_map_from_def(struct bpf_map *map, const struct btf_map_def *def
 	map->btf_key_type_id = def->key_type_id;
 	map->btf_value_type_id = def->value_type_id;
 
+	/* auto-adjust BPF ringbuf map max_entries to be a multiple of page size */
+	if (map->def.type == BPF_MAP_TYPE_RINGBUF)
+		map->def.max_entries = adjust_ringbuf_sz(map->def.max_entries);
+
 	if (def->parts & MAP_DEF_MAP_TYPE)
 		pr_debug("map '%s': found type = %u.\n", map->name, def->map_type);
 
@@ -4317,9 +4352,15 @@ struct bpf_map *bpf_map__inner_map(struct bpf_map *map)
 
 int bpf_map__set_max_entries(struct bpf_map *map, __u32 max_entries)
 {
-	if (map->fd >= 0)
+	if (map->obj->loaded)
 		return libbpf_err(-EBUSY);
+
 	map->def.max_entries = max_entries;
+
+	/* auto-adjust BPF ringbuf map max_entries to be a multiple of page size */
+	if (map->def.type == BPF_MAP_TYPE_RINGBUF)
+		map->def.max_entries = adjust_ringbuf_sz(map->def.max_entries);
+
 	return 0;
 }
 
@@ -4875,37 +4916,6 @@ bpf_object__populate_internal_map(struct bpf_object *obj, struct bpf_map *map)
 
 static void bpf_map__destroy(struct bpf_map *map);
 
-static size_t adjust_ringbuf_sz(size_t sz)
-{
-	__u32 page_sz = sysconf(_SC_PAGE_SIZE);
-	__u32 mul;
-
-	/* if user forgot to set any size, make sure they see error */
-	if (sz == 0)
-		return 0;
-	/* Kernel expects BPF_MAP_TYPE_RINGBUF's max_entries to be
-	 * a power-of-2 multiple of kernel's page size. If user diligently
-	 * satisified these conditions, pass the size through.
-	 */
-	if ((sz % page_sz) == 0 && is_pow_of_2(sz / page_sz))
-		return sz;
-
-	/* Otherwise find closest (page_sz * power_of_2) product bigger than
-	 * user-set size to satisfy both user size request and kernel
-	 * requirements and substitute correct max_entries for map creation.
-	 */
-	for (mul = 1; mul <= UINT_MAX / page_sz; mul <<= 1) {
-		if (mul * page_sz > sz)
-			return mul * page_sz;
-	}
-
-	/* if it's impossible to satisfy the conditions (i.e., user size is
-	 * very close to UINT_MAX but is not a power-of-2 multiple of
-	 * page_size) then just return original size and let kernel reject it
-	 */
-	return sz;
-}
-
 static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, bool is_inner)
 {
 	LIBBPF_OPTS(bpf_map_create_opts, create_attr);
@@ -4944,9 +4954,6 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
 	}
 
 	switch (def->type) {
-	case BPF_MAP_TYPE_RINGBUF:
-		map->def.max_entries = adjust_ringbuf_sz(map->def.max_entries);
-		/* fallthrough */
 	case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
 	case BPF_MAP_TYPE_CGROUP_ARRAY:
 	case BPF_MAP_TYPE_STACK_TRACE:

tools/testing/selftests/bpf/prog_tests/ringbuf_multi.c

@@ -50,6 +50,13 @@ void test_ringbuf_multi(void)
 	if (CHECK(!skel, "skel_open", "skeleton open failed\n"))
 		return;
 
+	/* validate ringbuf size adjustment logic */
+	ASSERT_EQ(bpf_map__max_entries(skel->maps.ringbuf1), page_size, "rb1_size_before");
+	ASSERT_OK(bpf_map__set_max_entries(skel->maps.ringbuf1, page_size + 1), "rb1_resize");
+	ASSERT_EQ(bpf_map__max_entries(skel->maps.ringbuf1), 2 * page_size, "rb1_size_after");
+	ASSERT_OK(bpf_map__set_max_entries(skel->maps.ringbuf1, page_size), "rb1_reset");
+	ASSERT_EQ(bpf_map__max_entries(skel->maps.ringbuf1), page_size, "rb1_size_final");
+
 	proto_fd = bpf_map_create(BPF_MAP_TYPE_RINGBUF, NULL, 0, 0, page_size, NULL);
 	if (CHECK(proto_fd < 0, "bpf_map_create", "bpf_map_create failed\n"))
 		goto cleanup;
@@ -65,6 +72,10 @@ void test_ringbuf_multi(void)
 	close(proto_fd);
 	proto_fd = -1;
 
+	/* make sure we can't resize ringbuf after object load */
+	if (!ASSERT_ERR(bpf_map__set_max_entries(skel->maps.ringbuf1, 3 * page_size), "rb1_resize_after_load"))
+		goto cleanup;
+
 	/* only trigger BPF program for current process */
 	skel->bss->pid = getpid();