/
kprobe_test.go
429 lines (344 loc) · 11.4 KB
/
kprobe_test.go
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package link
import (
"errors"
"fmt"
"os"
"testing"
qt "github.com/frankban/quicktest"
"github.com/cilium/ebpf"
"github.com/cilium/ebpf/asm"
"github.com/cilium/ebpf/internal/testutils"
"github.com/cilium/ebpf/internal/unix"
)
// Global symbol, present on all tested kernels.
var ksym = "vprintk"
// Collection of various symbols present in all tested kernels.
// Compiler optimizations result in different names for these symbols.
var symTests = []string{
"async_resume.cold", // marked with 'cold' gcc attribute, unlikely to be executed
"echo_char.isra.0", // function optimized by -fipa-sra
"get_buffer.constprop.0", // optimized function with constant operands
"unregister_kprobes.part.0", // function body that was split and partially inlined
}
func TestKprobe(t *testing.T) {
prog := mustLoadProgram(t, ebpf.Kprobe, 0, "")
for _, tt := range symTests {
t.Run(tt, func(t *testing.T) {
k, err := Kprobe(tt, prog, nil)
if err != nil {
t.Fatal(err)
}
defer k.Close()
})
}
c := qt.New(t)
k, err := Kprobe("bogus", prog, nil)
c.Assert(err, qt.ErrorIs, os.ErrNotExist, qt.Commentf("got error: %s", err))
if k != nil {
k.Close()
}
k, err = Kprobe(ksym, prog, nil)
c.Assert(err, qt.IsNil)
defer k.Close()
testLink(t, k, prog)
}
func TestKretprobe(t *testing.T) {
prog := mustLoadProgram(t, ebpf.Kprobe, 0, "")
for _, tt := range symTests {
t.Run(tt, func(t *testing.T) {
k, err := Kretprobe(tt, prog, nil)
if err != nil {
t.Fatal(err)
}
defer k.Close()
})
}
c := qt.New(t)
k, err := Kretprobe("bogus", prog, nil)
c.Assert(err, qt.ErrorIs, os.ErrNotExist, qt.Commentf("got error: %s", err))
if k != nil {
k.Close()
}
k, err = Kretprobe(ksym, prog, nil)
c.Assert(err, qt.IsNil)
defer k.Close()
testLink(t, k, prog)
}
func TestKprobeErrors(t *testing.T) {
c := qt.New(t)
// Invalid Kprobe incantations. Kretprobe uses the same code paths
// with a different ret flag.
_, err := Kprobe("", nil, nil) // empty symbol
c.Assert(errors.Is(err, errInvalidInput), qt.IsTrue)
_, err = Kprobe("_", nil, nil) // empty prog
c.Assert(errors.Is(err, errInvalidInput), qt.IsTrue)
_, err = Kprobe(".", &ebpf.Program{}, nil) // illegal chars in symbol
c.Assert(errors.Is(err, errInvalidInput), qt.IsTrue)
_, err = Kprobe("foo", &ebpf.Program{}, nil) // wrong prog type
c.Assert(errors.Is(err, errInvalidInput), qt.IsTrue)
}
// Test k(ret)probe creation using perf_kprobe PMU.
func TestKprobeCreatePMU(t *testing.T) {
// Requires at least 4.17 (e12f03d7031a "perf/core: Implement the 'perf_kprobe' PMU")
testutils.SkipOnOldKernel(t, "4.17", "perf_kprobe PMU")
c := qt.New(t)
// kprobe happy path. printk is always present.
pk, err := pmuKprobe(probeArgs{symbol: ksym})
c.Assert(err, qt.IsNil)
defer pk.Close()
c.Assert(pk.typ, qt.Equals, kprobeEvent)
// kretprobe happy path.
pr, err := pmuKprobe(probeArgs{symbol: ksym, ret: true})
c.Assert(err, qt.IsNil)
defer pr.Close()
c.Assert(pr.typ, qt.Equals, kretprobeEvent)
// Expect os.ErrNotExist when specifying a non-existent kernel symbol
// on kernels 4.17 and up.
_, err = pmuKprobe(probeArgs{symbol: "bogus"})
c.Assert(errors.Is(err, os.ErrNotExist), qt.IsTrue, qt.Commentf("got error: %s", err))
// A kernel bug was fixed in 97c753e62e6c where EINVAL was returned instead
// of ENOENT, but only for kretprobes.
_, err = pmuKprobe(probeArgs{symbol: "bogus", ret: true})
c.Assert(errors.Is(err, os.ErrNotExist), qt.IsTrue, qt.Commentf("got error: %s", err))
}
// Test fallback behaviour on kernels without perf_kprobe PMU available.
func TestKprobePMUUnavailable(t *testing.T) {
c := qt.New(t)
pk, err := pmuKprobe(probeArgs{symbol: ksym})
if err == nil {
pk.Close()
t.Skipf("Kernel supports perf_kprobe PMU, not asserting error.")
}
// Only allow a PMU creation with a valid kernel symbol to fail with ErrNotSupported.
c.Assert(errors.Is(err, ErrNotSupported), qt.IsTrue, qt.Commentf("got error: %s", err))
}
func BenchmarkKprobeCreatePMU(b *testing.B) {
for n := 0; n < b.N; n++ {
pr, err := pmuKprobe(probeArgs{symbol: ksym})
if err != nil {
b.Error("error creating perf_kprobe PMU:", err)
}
if err := pr.Close(); err != nil {
b.Error("error closing perf_kprobe PMU:", err)
}
}
}
// Test tracefs k(ret)probe creation on all kernel versions.
func TestKprobeTraceFS(t *testing.T) {
c := qt.New(t)
// Open and close tracefs k(ret)probes, checking all errors.
kp, err := tracefsKprobe(probeArgs{symbol: ksym})
c.Assert(err, qt.IsNil)
c.Assert(kp.Close(), qt.IsNil)
c.Assert(kp.typ, qt.Equals, kprobeEvent)
kp, err = tracefsKprobe(probeArgs{symbol: ksym, ret: true})
c.Assert(err, qt.IsNil)
c.Assert(kp.Close(), qt.IsNil)
c.Assert(kp.typ, qt.Equals, kretprobeEvent)
// Create two identical trace events, ensure their IDs differ.
k1, err := tracefsKprobe(probeArgs{symbol: ksym})
c.Assert(err, qt.IsNil)
defer k1.Close()
c.Assert(k1.tracefsID, qt.Not(qt.Equals), 0)
k2, err := tracefsKprobe(probeArgs{symbol: ksym})
c.Assert(err, qt.IsNil)
defer k2.Close()
c.Assert(k2.tracefsID, qt.Not(qt.Equals), 0)
// Compare the kprobes' tracefs IDs.
c.Assert(k1.tracefsID, qt.Not(qt.CmpEquals()), k2.tracefsID)
// Prepare probe args.
args := probeArgs{group: "testgroup", symbol: "symbol"}
// Write a k(ret)probe event for a non-existing symbol.
err = createTraceFSProbeEvent(kprobeType, args)
c.Assert(errors.Is(err, os.ErrNotExist), qt.IsTrue, qt.Commentf("got error: %s", err))
// A kernel bug was fixed in 97c753e62e6c where EINVAL was returned instead
// of ENOENT, but only for kretprobes.
args.ret = true
err = createTraceFSProbeEvent(kprobeType, args)
c.Assert(errors.Is(err, os.ErrNotExist), qt.IsTrue, qt.Commentf("got error: %s", err))
}
func BenchmarkKprobeCreateTraceFS(b *testing.B) {
for n := 0; n < b.N; n++ {
// Include <tracefs>/kprobe_events operations in the benchmark loop
// because we create one per perf event.
pr, err := tracefsKprobe(probeArgs{symbol: ksym})
if err != nil {
b.Error("error creating tracefs perf event:", err)
}
if err := pr.Close(); err != nil {
b.Error("error closing tracefs perf event:", err)
}
}
}
// Test k(ret)probe creation writing directly to <tracefs>/kprobe_events.
// Only runs on 5.0 and over. Earlier versions ignored writes of duplicate
// events, while 5.0 started returning -EEXIST when a kprobe event already
// exists.
func TestKprobeCreateTraceFS(t *testing.T) {
testutils.SkipOnOldKernel(t, "5.0", "<tracefs>/kprobe_events doesn't reject duplicate events")
c := qt.New(t)
pg, _ := randomGroup("ebpftest")
rg, _ := randomGroup("ebpftest")
// Tee up cleanups in case any of the Asserts abort the function.
defer func() {
_ = closeTraceFSProbeEvent(kprobeType, pg, ksym)
_ = closeTraceFSProbeEvent(kprobeType, rg, ksym)
}()
// Prepare probe args.
args := probeArgs{group: pg, symbol: ksym}
// Create a kprobe.
err := createTraceFSProbeEvent(kprobeType, args)
c.Assert(err, qt.IsNil)
// Attempt to create an identical kprobe using tracefs,
// expect it to fail with os.ErrExist.
err = createTraceFSProbeEvent(kprobeType, args)
c.Assert(errors.Is(err, os.ErrExist), qt.IsTrue,
qt.Commentf("expected consecutive kprobe creation to contain os.ErrExist, got: %v", err))
// Expect a successful close of the kprobe.
c.Assert(closeTraceFSProbeEvent(kprobeType, pg, ksym), qt.IsNil)
args.group = rg
args.ret = true
// Same test for a kretprobe.
err = createTraceFSProbeEvent(kprobeType, args)
c.Assert(err, qt.IsNil)
err = createTraceFSProbeEvent(kprobeType, args)
c.Assert(os.IsExist(err), qt.IsFalse,
qt.Commentf("expected consecutive kretprobe creation to contain os.ErrExist, got: %v", err))
// Expect a successful close of the kretprobe.
c.Assert(closeTraceFSProbeEvent(kprobeType, rg, ksym), qt.IsNil)
}
func TestKprobeTraceFSGroup(t *testing.T) {
c := qt.New(t)
// Expect <prefix>_<16 random hex chars>.
g, err := randomGroup("ebpftest")
c.Assert(err, qt.IsNil)
c.Assert(g, qt.Matches, `ebpftest_[a-f0-9]{16}`)
// Expect error when the generator's output exceeds 63 characters.
p := make([]byte, 47) // 63 - 17 (length of the random suffix and underscore) + 1
for i := range p {
p[i] = byte('a')
}
_, err = randomGroup(string(p))
c.Assert(err, qt.Not(qt.IsNil))
// Reject non-alphanumeric characters.
_, err = randomGroup("/")
c.Assert(err, qt.Not(qt.IsNil))
}
func TestDetermineRetprobeBit(t *testing.T) {
testutils.SkipOnOldKernel(t, "4.17", "perf_kprobe PMU")
c := qt.New(t)
rpk, err := kretprobeBit()
c.Assert(err, qt.IsNil)
c.Assert(rpk, qt.Equals, uint64(0))
rpu, err := uretprobeBit()
c.Assert(err, qt.IsNil)
c.Assert(rpu, qt.Equals, uint64(0))
}
func TestKprobeProgramCall(t *testing.T) {
m, p := newUpdaterMapProg(t, ebpf.Kprobe)
// Open Kprobe on `sys_getpid` and attach it
// to the ebpf program created above.
k, err := Kprobe("sys_getpid", p, nil)
if err != nil {
t.Fatal(err)
}
// Trigger ebpf program call.
unix.Getpid()
// Assert that the value at index 0 has been updated to 1.
assertMapValue(t, m, 0, 1)
// Detach the Kprobe.
if err := k.Close(); err != nil {
t.Fatal(err)
}
// Reset map value to 0 at index 0.
if err := m.Update(uint32(0), uint32(0), ebpf.UpdateExist); err != nil {
t.Fatal(err)
}
// Retrigger the ebpf program call.
unix.Getpid()
// Assert that this time the value has not been updated.
assertMapValue(t, m, 0, 0)
}
func newUpdaterMapProg(t *testing.T, typ ebpf.ProgramType) (*ebpf.Map, *ebpf.Program) {
// Create ebpf map. Will contain only one key with initial value 0.
m, err := ebpf.NewMap(&ebpf.MapSpec{
Type: ebpf.Array,
KeySize: 4,
ValueSize: 4,
MaxEntries: 1,
})
if err != nil {
t.Fatal(err)
}
// Create ebpf program. When called, will set the value of key 0 in
// the map created above to 1.
p, err := ebpf.NewProgram(&ebpf.ProgramSpec{
Type: typ,
Instructions: asm.Instructions{
// u32 key = 0
asm.Mov.Imm(asm.R1, 0),
asm.StoreMem(asm.RFP, -4, asm.R1, asm.Word),
// u32 val = 1
asm.Mov.Imm(asm.R1, 1),
asm.StoreMem(asm.RFP, -8, asm.R1, asm.Word),
// bpf_map_update_elem(...)
asm.Mov.Reg(asm.R2, asm.RFP),
asm.Add.Imm(asm.R2, -4),
asm.Mov.Reg(asm.R3, asm.RFP),
asm.Add.Imm(asm.R3, -8),
asm.LoadMapPtr(asm.R1, m.FD()),
asm.Mov.Imm(asm.R4, 0),
asm.FnMapUpdateElem.Call(),
// exit 0
asm.Mov.Imm(asm.R0, 0),
asm.Return(),
},
License: "Dual MIT/GPL",
})
if err != nil {
t.Fatal(err)
}
// Close the program and map on test teardown.
t.Cleanup(func() {
m.Close()
p.Close()
})
return m, p
}
func assertMapValue(t *testing.T, m *ebpf.Map, k, v uint32) {
var val uint32
if err := m.Lookup(k, &val); err != nil {
t.Fatal(err)
}
if val != v {
t.Fatalf("unexpected value: want '%d', got '%d'", v, val)
}
}
func TestKprobeCookie(t *testing.T) {
testutils.SkipOnOldKernel(t, "5.15", "bpf_perf_link")
prog := mustLoadProgram(t, ebpf.Kprobe, 0, "")
k, err := Kprobe(ksym, prog, &KprobeOptions{Cookie: 1000})
if err != nil {
t.Fatal(err)
}
k.Close()
}
func TestKprobeToken(t *testing.T) {
tests := []struct {
args probeArgs
expected string
}{
{probeArgs{symbol: "symbol"}, "symbol"},
{probeArgs{symbol: "symbol", offset: 1}, "symbol+0x1"},
{probeArgs{symbol: "symbol", offset: 65535}, "symbol+0xffff"},
{probeArgs{symbol: "symbol", offset: 65536}, "symbol+0x10000"},
}
for i, tt := range tests {
t.Run(fmt.Sprint(i), func(t *testing.T) {
po := kprobeToken(tt.args)
if tt.expected != po {
t.Errorf("Expected symbol+offset to be '%s', got '%s'", tt.expected, po)
}
})
}
}