Fix wrong behavior on s390x

asm/instruction.go

@@ -3,6 +3,7 @@ package asm
 import (
 	"encoding/binary"
 	"fmt"
+	"github.com/cilium/ebpf/internal"
 	"io"
 	"math"
 	"strings"
@@ -433,15 +434,27 @@ type bpfInstruction struct {
 type bpfRegisters uint8
 
 func newBPFRegisters(dst, src Register) bpfRegisters {
-	return bpfRegisters((src << 4) | (dst & 0xF))
+	if internal.NativeEndian == binary.LittleEndian {
+		return bpfRegisters((src << 4) | (dst & 0xF))
+	} else {
+		return bpfRegisters((dst << 4) | (src & 0xF))
+	}
 }
 
 func (r bpfRegisters) Dst() Register {
-	return Register(r & 0xF)
+	if internal.NativeEndian == binary.LittleEndian {
+		return Register(r & 0xF)
+	}else {
+		return Register(r >> 4)
+	}
 }
 
 func (r bpfRegisters) Src() Register {
-	return Register(r >> 4)
+	if internal.NativeEndian == binary.LittleEndian {
+		return Register(r >> 4)
+	} else {
+		return Register(r & 0xf)
+	}
 }
 
 type unreferencedSymbolError struct {

asm/instruction_test.go

@@ -8,6 +8,8 @@ import (
 	"io/ioutil"
 	"math"
 	"testing"
+
+	"github.com/cilium/ebpf/internal"
 )
 
 var test64bitImmProg = []byte{
@@ -179,3 +181,32 @@ func ExampleInstructions_Format() {
 	// 	1: LdImmDW dst: r0 imm: 42
 	// 	3: Exit
 }
+
+var testSrcDstProg = []byte{
+	// on little-endian: r0 = r1
+	// on big-endian: be: r1 = r0
+	0xbf, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+}
+
+func TestReadSrcDst(t *testing.T) {
+	var ins Instruction
+	n, err := ins.Unmarshal(bytes.NewReader(testSrcDstProg), binary.BigEndian)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if want := uint64(InstructionSize); n != want {
+		t.Errorf("Expected %d bytes to be read, got %d", want, n)
+	}
+	var expDst, expSrc Register
+	if internal.NativeEndian == binary.LittleEndian {
+		expDst, expSrc = 0, 1
+	} else {
+		expDst, expSrc = 1, 0
+	}
+	if ins.Dst != expDst {
+		t.Errorf("Expected destination to be %v, got %v", expDst, ins.Dst)
+	}
+	if ins.Src != expSrc {
+		t.Errorf("Expected source to be %v, got %v", expSrc, ins.Src)
+	}
+}

elf_reader_test.go

@@ -2,6 +2,7 @@ package ebpf
 
 import (
 	"flag"
+	"fmt"
 	"path/filepath"
 	"reflect"
 	"strings"
@@ -11,7 +12,8 @@ import (
 )
 
 func TestLoadCollectionSpec(t *testing.T) {
-	files, err := filepath.Glob("testdata/loader-*.elf")
+	pattern := fmt.Sprintf("testdata/loader-*-%s.elf", testutils.GetHostEndianness())
+	files, err := filepath.Glob(pattern)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -209,7 +211,8 @@ func TestCollectionSpecDetach(t *testing.T) {
 }
 
 func TestLoadInvalidMap(t *testing.T) {
-	_, err := LoadCollectionSpec("testdata/invalid_map.elf")
+	path := fmt.Sprintf("testdata/invalid_map-%s.elf", testutils.GetHostEndianness())
+	_, err := LoadCollectionSpec(path)
 	t.Log(err)
 	if err == nil {
 		t.Fatal("should be fail")

internal/btf/btf_test.go

@@ -53,7 +53,7 @@ func TestParseCurrentKernelBTF(t *testing.T) {
 }
 
 func TestLoadSpecFromElf(t *testing.T) {
-	fh, err := os.Open("../../testdata/loader-clang-9.elf")
+	fh, err := os.Open(fmt.Sprintf("../../testdata/loader-clang-9-%s.elf", testutils.GetHostEndianness()));
 	if err != nil {
 		t.Fatal(err)
 	}

internal/testutils/endianness.go

@@ -0,0 +1,15 @@
+package testutils
+
+import (
+        "encoding/binary"
+
+	"github.com/cilium/ebpf/internal"
+)
+
+func GetHostEndianness() string {
+	if internal.NativeEndian == binary.LittleEndian {
+		return "el"
+	} else {
+		return "eb"
+	}
+}

testdata/Makefile

@@ -1,19 +1,22 @@
 LLVM_PREFIX ?= /usr/bin
 CLANG ?= $(LLVM_PREFIX)/clang
+CFLAGS := -target bpf -O2 -g -Wall -Werror $(CFLAGS)
 
 .PHONY: all clean
-all: loader-clang-6.0.elf loader-clang-7.elf loader-clang-8.elf loader-clang-9.elf rewrite.elf invalid_map.elf
+all: loader-clang-6.0-el.elf loader-clang-7-el.elf loader-clang-8-el.elf loader-clang-9-el.elf rewrite-el.elf invalid_map-el.elf \
+	loader-clang-6.0-eb.elf loader-clang-7-eb.elf loader-clang-8-eb.elf loader-clang-9-eb.elf rewrite-eb.elf invalid_map-eb.elf
 
 clean:
 	-$(RM) *.elf
 
-loader-%.elf: loader.c
-	$* -target bpf -O2 -g \
-		-Wall -Werror \
-		-c $< -o $@
+loader-%-el.elf: loader.c
+	$* $(CFLAGS) -mlittle-endian -c $< -o $@
 
-%.elf : %.c
-	$(CLANG) -target bpf -O2 -g \
-		-Wall -Werror \
-		-c $< -o $@
+loader-%-eb.elf: loader.c
+	$* $(CFLAGS) -mbig-endian -c $< -o $@
 
+%-el.elf: %.c
+	$(CLANG) $(CFLAGS) -mlittle-endian -c $< -o $@
+
+%-eb.elf : %.c
+	$(CLANG) $(CFLAGS) -mbig-endian -c $< -o $@