Kernel Testing

// test_example.c
#include <kunit/test.h>

static void example_test(struct kunit *test)
{
    KUNIT_EXPECT_EQ(test, 1 + 1, 2);
    KUNIT_ASSERT_NOT_ERR_OR_NULL(test, kmalloc(16, GFP_KERNEL));
}

static struct kunit_case example_test_cases[] = {
    KUNIT_CASE(example_test),
    {}
};

static struct kunit_suite example_suite = {
    .name = "example",
    .test_cases = example_test_cases,
};
kunit_test_suite(example_suite);

MODULE_LICENSE("GPL");

# Makefile
obj-$(CONFIG_KUNIT) += test_example.o

# Run KUnit (in-tree)
./tools/testing/kunit/kunit.py run

# Run specific test
./tools/testing/kunit/kunit.py run --filter example

# With cross-compilation
./tools/testing/kunit/kunit.py run --cross_compile aarch64-linux-gnu- \
    --arch arm64

# Build all selftests
cd tools/testing/selftests
make -j$(nproc)

# Run all
make run_tests

# Run specific test
./memfd/memfd_test
./mount/run_unprivileged_remount.sh

tools/testing/selftests/mytest/
├── Makefile
├── mytest.c
└── config        # optional kconfig requirements

# tools/testing/selftests/mytest/Makefile
CFLAGS += -Wall
TEST_GEN_FILES := mytest
TEST_PROGS := mytest

include ../lib.mk

# Run from top-level
make -C tools/testing/selftests/mytest run_tests

# Install syzkaller
git clone https://github.com/google/syzkaller
cd syzkaller && make

# Manager config (manager.cfg)
{
    "target": "linux/amd64",
    "http": "127.0.0.1:56741",
    "workdir": "/tmp/syzkaller",
    "kernel_obj": "/path/to/kernel/build",
    "syzkaller": "/path/to/syzkaller",
    "procs": 8,
    "type": "qemu",
    "vm": {
        "count": 4,
        "kernel": "/path/to/bzImage",
        "cpu": 2,
        "mem": 2048
    }
}

# Start manager
./bin/syz-manager -config manager.cfg

# Reproduce a crash
./bin/syz-repro -config manager.cfg crash-report.txt

# Enable kcov on instrumented kernel
# CONFIG_KCOV=y in kernel config

# syzkaller uses kcov automatically
# Manual coverage via debugfs
ls /sys/kernel/debug/kcov/

# Build LTP
git clone https://github.com/linux-test-project/ltp
cd ltp
make autotools
./configure
make -j$(nproc)
make install

# Run syscall tests
cd /opt/ltp
./runltp -f syscalls

# Run specific test
./runltp -f syscalls -s pipe01

# Local kernel build test (simplified workflow)
# KernelCI tests patches against multiple defconfigs

# Submit build to KernelCI (project-specific tokens)
# See https://kernelci.org/docs/

# Check boot and kselftest results in KernelCI dashboard

Patch → build (allmodconfig) → boot test (QEMU) → kselftest → LTP subset

What to test?
├── Pure kernel function logic → KUnit
├── Userspace-visible behavior (syscall, ioctl) → kselftest
├── Security/crash finding → syzkaller + KASAN
├── Regression across distros → LTP
└── Upstream patch CI → KernelCI

CONFIG_KUNIT=y
CONFIG_KCOV=y
CONFIG_KASAN=y
CONFIG_DEBUG_INFO_DWARF5=y
CONFIG_FRAME_POINTER=y
CONFIG_FTRACE=y

make kvm_guest.config   # reasonable test config base
scripts/config --enable KUNIT KCOV KASAN
make olddefconfig