info: expose func info from ProgramInfo

`bpf_prog_info` supports func info since commit
torvalds/linux@838e96904ff3 ("bpf: Introduce bpf_func_info").

Signed-off-by: Leon Hwang <[email protected]>
Co-authored-by: Timo Beckers <[email protected]>

Author: Asphaltt

info.go

@@ -531,6 +531,39 @@ func (pi *ProgramInfo) KsymAddrs() ([]uintptr, bool) {
 	return addrs, pi.numKsymInfos > 0
 }
 
+// FuncInfos returns the offset and function information of all (sub)programs in
+// a BPF program.
+//
+// Available from 5.0.
+//
+// Requires CAP_SYS_ADMIN or equivalent for reading BTF information. Returns
+// ErrNotSupported if the program was created without BTF or if the kernel
+// doesn't support the field.
+func (pi *ProgramInfo) FuncInfos() (btf.FuncOffsets, error) {
+	id, ok := pi.BTFID()
+	if pi.numFuncInfos == 0 || !ok {
+		return nil, fmt.Errorf("program created without BTF or unsupported kernel: %w", ErrNotSupported)
+	}
+
+	h, err := btf.NewHandleFromID(id)
+	if err != nil {
+		return nil, fmt.Errorf("get BTF handle: %w", err)
+	}
+	defer h.Close()
+
+	spec, err := h.Spec(nil)
+	if err != nil {
+		return nil, fmt.Errorf("get BTF spec: %w", err)
+	}
+
+	return btf.LoadFuncInfos(
+		bytes.NewReader(pi.funcInfos),
+		internal.NativeEndian,
+		pi.numFuncInfos,
+		spec,
+	)
+}
+
 func scanFdInfo(fd *sys.FD, fields map[string]interface{}) error {
 	fh, err := os.Open(fmt.Sprintf("/proc/self/fdinfo/%d", fd.Int()))
 	if err != nil {

info_test.go

@@ -535,3 +535,30 @@ func TestProgInfoKsym(t *testing.T) {
 		qt.Assert(t, qt.Not(qt.Equals(addr, 0)))
 	}
 }
+
+func TestProgInfoFuncInfos(t *testing.T) {
+	testutils.SkipOnOldKernel(t, "5.0", "Program func info")
+
+	spec, err := LoadCollectionSpec(testutils.NativeFile(t, "testdata/loader-%s.elf"))
+	qt.Assert(t, qt.IsNil(err))
+
+	var obj struct {
+		Prog *Program `ebpf:"xdp_prog"`
+	}
+	err = spec.LoadAndAssign(&obj, nil)
+	testutils.SkipIfNotSupported(t, err)
+	qt.Assert(t, qt.IsNil(err))
+	defer obj.Prog.Close()
+
+	info, err := obj.Prog.Info()
+	qt.Assert(t, qt.IsNil(err))
+
+	funcs, err := info.FuncInfos()
+	qt.Assert(t, qt.IsNil(err))
+
+	qt.Assert(t, qt.HasLen(funcs, 5))
+	for _, fo := range funcs {
+		qt.Assert(t, qt.IsNotNil(fo.Func))
+		qt.Assert(t, qt.Not(qt.Equals(fo.Func.Name, "")))
+	}
+}