ftrace_direct (used by bpf trampoline) conflicts with live patch

.github/actions/vmtest/action.yml

@@ -0,0 +1,35 @@
+name: 'vmtest'
+description: 'Build + run vmtest'
+inputs:
+  arch:
+    description: 'what arch to test'
+    required: true
+    default: 'x86_64'
+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 }}
+    - name: Build selftests
+      shell: bash
+      run: ${GITHUB_ACTION_PATH}/build_selftests.sh
+      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 +1,17 @@
+#!/bin/bash
+
+set -euo pipefail
+
+ARCH="$1"
+
+THISDIR="$(cd $(dirname $0) && pwd)"
+
+source "${THISDIR}"/helpers.sh
+
+travis_fold start build_kernel "Building kernel"
+
+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 +1,42 @@
+#!/bin/bash
+
+set -euo pipefail
+
+THISDIR="$(cd $(dirname $0) && pwd)"
+
+source "${THISDIR}"/helpers.sh
+
+travis_fold start prepare_selftests "Building selftests"
+
+LLVM_VER=15
+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 +1,50 @@
+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 ${{ matrix.runs_on }} + selftests
+    timeout-minutes: 100
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - kernel: 'LATEST'
+            runs_on: ubuntu-latest
+            arch: 'x86_64'
+          - kernel: 'LATEST'
+            runs_on: z15
+            arch: 's390x'
+    env:
+      AUTHOR_EMAIL: "$(git log -1 --pretty=\"%aE\")"
+      KERNEL: LATEST
+      REPO_ROOT: ${{ github.workspace }}
+      REPO_PATH: ""
+    steps:
+      - uses: actions/checkout@v2
+      - if: ${{ github.repository != 'kernel-patches/bpf' && github.repository != 'kernel-patches/bpf-rc' }}
+        name: Download bpf-next tree
+        uses: libbpf/ci/get-linux-source@master
+        with:
+          dest: '.kernel'
+      - if: ${{ github.repository != 'kernel-patches/bpf' && github.repository != 'kernel-patches/bpf-rc' }}
+        name: Move linux source in place
+        shell: bash
+        run: |
+          rm -rf .kernel/.git
+          cp -rf .kernel/. .
+          rm -rf .kernel
+      - uses: libbpf/ci/patch-kernel@master
+        with:
+          patches-root: '${{ github.workspace }}/travis-ci/diffs'
+          repo-root: '${{ github.workspace }}'
+      - uses: ./.github/actions/vmtest
+        with:
+          arch: ${{ matrix.arch }}

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.

include/linux/ftrace.h

@@ -326,6 +326,8 @@ struct dyn_ftrace;
 extern int ftrace_direct_func_count;
 int register_ftrace_direct(unsigned long ip, unsigned long addr);
 int unregister_ftrace_direct(unsigned long ip, unsigned long addr);
+int register_ftrace_direct_no_ipmodify(unsigned long ip, unsigned long addr);
+int unregister_ftrace_direct_no_ipmodify(unsigned long ip, unsigned long addr);
 int modify_ftrace_direct(unsigned long ip, unsigned long old_addr, unsigned long new_addr);
 struct ftrace_direct_func *ftrace_find_direct_func(unsigned long addr);
 int ftrace_modify_direct_caller(struct ftrace_func_entry *entry,

kernel/bpf/trampoline.c

@@ -123,7 +123,7 @@ static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
 	int ret;
 
 	if (tr->func.ftrace_managed)
-		ret = unregister_ftrace_direct((long)ip, (long)old_addr);
+		ret = unregister_ftrace_direct_no_ipmodify((long)ip, (long)old_addr);
 	else
 		ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL);
 
@@ -159,7 +159,7 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
 		return -ENOENT;
 
 	if (tr->func.ftrace_managed)
-		ret = register_ftrace_direct((long)ip, (long)new_addr);
+		ret = register_ftrace_direct_no_ipmodify((long)ip, (long)new_addr);
 	else
 		ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
 

kernel/trace/ftrace.c

@@ -2467,6 +2467,20 @@ struct ftrace_ops direct_ops = {
 	 */
 	.trampoline	= FTRACE_REGS_ADDR,
 };
+
+struct ftrace_ops no_ipmodify_direct_ops = {
+	.func		= call_direct_funcs,
+	.flags		= FTRACE_OPS_FL_DIRECT | FTRACE_OPS_FL_SAVE_REGS
+			  | FTRACE_OPS_FL_PERMANENT,
+	/*
+	 * By declaring the main trampoline as this trampoline
+	 * it will never have one allocated for it. Allocated
+	 * trampolines should not call direct functions.
+	 * The direct_ops should only be called by the builtin
+	 * ftrace_regs_caller trampoline.
+	 */
+	.trampoline	= FTRACE_REGS_ADDR,
+};
 #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
 
 /**
@@ -5126,6 +5140,9 @@ static struct ftrace_direct_func *ftrace_alloc_direct_func(unsigned long addr)
 	return direct;
 }
 
+static int __register_ftrace_direct(unsigned long ip, unsigned long addr,
+				    struct ftrace_ops *ops);
+
 /**
  * register_ftrace_direct - Call a custom trampoline directly
  * @ip: The address of the nop at the beginning of a function
@@ -5144,6 +5161,12 @@ static struct ftrace_direct_func *ftrace_alloc_direct_func(unsigned long addr)
  *  -ENOMEM - There was an allocation failure.
  */
 int register_ftrace_direct(unsigned long ip, unsigned long addr)
+{
+	return __register_ftrace_direct(ip, addr, &direct_ops);
+}
+
+static int __register_ftrace_direct(unsigned long ip, unsigned long addr,
+				    struct ftrace_ops *ops)
 {
 	struct ftrace_direct_func *direct;
 	struct ftrace_func_entry *entry;
@@ -5194,14 +5217,14 @@ int register_ftrace_direct(unsigned long ip, unsigned long addr)
 	if (!entry)
 		goto out_unlock;
 
-	ret = ftrace_set_filter_ip(&direct_ops, ip, 0, 0);
+	ret = ftrace_set_filter_ip(ops, ip, 0, 0);
 	if (ret)
 		remove_hash_entry(direct_functions, entry);
 
-	if (!ret && !(direct_ops.flags & FTRACE_OPS_FL_ENABLED)) {
-		ret = register_ftrace_function(&direct_ops);
+	if (!ret && !(ops->flags & FTRACE_OPS_FL_ENABLED)) {
+		ret = register_ftrace_function(ops);
 		if (ret)
-			ftrace_set_filter_ip(&direct_ops, ip, 1, 0);
+			ftrace_set_filter_ip(ops, ip, 1, 0);
 	}
 
 	if (ret) {
@@ -5230,6 +5253,29 @@ int register_ftrace_direct(unsigned long ip, unsigned long addr)
 }
 EXPORT_SYMBOL_GPL(register_ftrace_direct);
 
+/**
+ * register_ftrace_direct_no_ipmodify - Call a custom trampoline directly.
+ * The custom trampoline should not use IP_MODIFY.
+ * @ip: The address of the nop at the beginning of a function
+ * @addr: The address of the trampoline to call at @ip
+ *
+ * This is used to connect a direct call from the nop location (@ip)
+ * at the start of ftrace traced functions. The location that it calls
+ * (@addr) must be able to handle a direct call, and save the parameters
+ * of the function being traced, and restore them (or inject new ones
+ * if needed), before returning.
+ *
+ * Returns:
+ *  0 on success
+ *  -EBUSY - Another direct function is already attached (there can be only one)
+ *  -ENODEV - @ip does not point to a ftrace nop location (or not supported)
+ *  -ENOMEM - There was an allocation failure.
+ */
+int register_ftrace_direct_no_ipmodify(unsigned long ip, unsigned long addr)
+{
+	return __register_ftrace_direct(ip, addr, &no_ipmodify_direct_ops);
+}
+
 static struct ftrace_func_entry *find_direct_entry(unsigned long *ip,
 						   struct dyn_ftrace **recp)
 {
@@ -5257,7 +5303,21 @@ static struct ftrace_func_entry *find_direct_entry(unsigned long *ip,
 	return entry;
 }
 
+static int __unregister_ftrace_direct(unsigned long ip, unsigned long addr,
+				      struct ftrace_ops *ops);
+
 int unregister_ftrace_direct(unsigned long ip, unsigned long addr)
+{
+	return __unregister_ftrace_direct(ip, addr, &direct_ops);
+}
+
+int unregister_ftrace_direct_no_ipmodify(unsigned long ip, unsigned long addr)
+{
+	return __unregister_ftrace_direct(ip, addr, &no_ipmodify_direct_ops);
+}
+
+static int __unregister_ftrace_direct(unsigned long ip, unsigned long addr,
+				      struct ftrace_ops *ops)
 {
 	struct ftrace_direct_func *direct;
 	struct ftrace_func_entry *entry;
@@ -5274,11 +5334,11 @@ int unregister_ftrace_direct(unsigned long ip, unsigned long addr)
 	if (!entry)
 		goto out_unlock;
 
-	hash = direct_ops.func_hash->filter_hash;
+	hash = ops->func_hash->filter_hash;
 	if (hash->count == 1)
-		unregister_ftrace_function(&direct_ops);
+		unregister_ftrace_function(ops);
 
-	ret = ftrace_set_filter_ip(&direct_ops, ip, 1, 0);
+	ret = ftrace_set_filter_ip(ops, ip, 1, 0);
 
 	WARN_ON(ret);