This patch to libgo changes the way that GNU/Linux netlink code is handled on big-endian systems. Rather than test whether the system is big- or little-endian, this code simply uses the native endianness, whatever it is, via the unsafe package. Bootstrapped and ran Go testsuite on x86_64-unknown-linux-gnu and powerpc64-unknown-linux-gnu. Committed to mainline and 4.7 branch.
Ian
Index: libgo/configure.ac =================================================================== --- libgo/configure.ac (revision 186144) +++ libgo/configure.ac (working copy) @@ -400,12 +400,6 @@ dnl Test if -lrt is required for sched_y AC_SEARCH_LIBS([sched_yield], [rt]) AC_C_BIGENDIAN -case $ac_cv_c_bigendian in - yes) GO_BIGENDIAN=true ;; - no) GO_BIGENDIAN=false ;; - *) AC_MSG_ERROR([unknown endianness]) ;; -esac -AC_SUBST(GO_BIGENDIAN) GCC_CHECK_UNWIND_GETIPINFO Index: libgo/go/net/interface_linux.go =================================================================== --- libgo/go/net/interface_linux.go (revision 186123) +++ libgo/go/net/interface_linux.go (working copy) @@ -64,11 +64,7 @@ func newLink(ifim *syscall.IfInfomsg, at case syscall.IFLA_IFNAME: ifi.Name = string(a.Value[:len(a.Value)-1]) case syscall.IFLA_MTU: - if syscall.BigEndian { - ifi.MTU = int(uint32(a.Value[0])<<24 | uint32(a.Value[1])<<16 | uint32(a.Value[2])<<8 | uint32(a.Value[3])) - } else { - ifi.MTU = int(uint32(a.Value[3])<<24 | uint32(a.Value[2])<<16 | uint32(a.Value[1])<<8 | uint32(a.Value[0])) - } + ifi.MTU = int(*(*uint32)(unsafe.Pointer(&a.Value[:4][0]))) } } return ifi @@ -197,15 +193,14 @@ func parseProcNetIGMP(path string, ifi * name = f[1] case len(f[0]) == 8: if ifi == nil || name == ifi.Name { + // The Linux kernel puts the IP + // address in /proc/net/igmp in native + // endianness. for i := 0; i+1 < len(f[0]); i += 2 { b[i/2], _ = xtoi2(f[0][i:i+2], 0) } - var ifma IPAddr - if syscall.BigEndian { - ifma = IPAddr{IP: IPv4(b[0], b[1], b[2], b[3])} - } else { - ifma = IPAddr{IP: IPv4(b[3], b[2], b[1], b[0])} - } + i := *(*uint32)(unsafe.Pointer(&b[:4][0])) + ifma := IPAddr{IP: IPv4(byte(i>>24), byte(i>>16), byte(i>>8), byte(i))} ifmat = append(ifmat, ifma.toAddr()) } } Index: libgo/go/syscall/netlink_linux.go =================================================================== --- libgo/go/syscall/netlink_linux.go (revision 186123) +++ libgo/go/syscall/netlink_linux.go (working copy) @@ -30,43 +30,12 @@ type NetlinkRouteRequest struct { func (rr *NetlinkRouteRequest) toWireFormat() []byte { b := make([]byte, rr.Header.Len) - if BigEndian { - b[0] = byte(rr.Header.Len >> 24) - b[1] = byte(rr.Header.Len >> 16) - b[2] = byte(rr.Header.Len >> 8) - b[3] = byte(rr.Header.Len) - b[4] = byte(rr.Header.Type >> 8) - b[5] = byte(rr.Header.Type) - b[6] = byte(rr.Header.Flags >> 8) - b[7] = byte(rr.Header.Flags) - b[8] = byte(rr.Header.Seq >> 24) - b[9] = byte(rr.Header.Seq >> 16) - b[10] = byte(rr.Header.Seq >> 8) - b[11] = byte(rr.Header.Seq) - b[12] = byte(rr.Header.Pid >> 24) - b[13] = byte(rr.Header.Pid >> 16) - b[14] = byte(rr.Header.Pid >> 8) - b[15] = byte(rr.Header.Pid) - b[16] = byte(rr.Data.Family) - } else { - b[0] = byte(rr.Header.Len) - b[1] = byte(rr.Header.Len >> 8) - b[2] = byte(rr.Header.Len >> 16) - b[3] = byte(rr.Header.Len >> 24) - b[4] = byte(rr.Header.Type) - b[5] = byte(rr.Header.Type >> 8) - b[6] = byte(rr.Header.Flags) - b[7] = byte(rr.Header.Flags >> 8) - b[8] = byte(rr.Header.Seq) - b[9] = byte(rr.Header.Seq >> 8) - b[10] = byte(rr.Header.Seq >> 16) - b[11] = byte(rr.Header.Seq >> 24) - b[12] = byte(rr.Header.Pid) - b[13] = byte(rr.Header.Pid >> 8) - b[14] = byte(rr.Header.Pid >> 16) - b[15] = byte(rr.Header.Pid >> 24) - b[16] = byte(rr.Data.Family) - } + *(*uint32)(unsafe.Pointer(&b[0:4][0])) = rr.Header.Len + *(*uint16)(unsafe.Pointer(&b[4:6][0])) = rr.Header.Type + *(*uint16)(unsafe.Pointer(&b[6:8][0])) = rr.Header.Flags + *(*uint32)(unsafe.Pointer(&b[8:12][0])) = rr.Header.Seq + *(*uint32)(unsafe.Pointer(&b[12:16][0])) = rr.Header.Pid + b[16] = byte(rr.Data.Family) return b } Index: libgo/Makefile.am =================================================================== --- libgo/Makefile.am (revision 186123) +++ libgo/Makefile.am (working copy) @@ -1559,7 +1559,6 @@ s-syscall_arch: Makefile echo "package syscall" > syscall_arch.go.tmp echo 'const ARCH = "'$(GOARCH)'"' >> syscall_arch.go.tmp echo 'const OS = "'$(GOOS)'"' >> syscall_arch.go.tmp - echo 'const BigEndian = $(GO_BIGENDIAN)' >> syscall_arch.go.tmp $(SHELL) $(srcdir)/../move-if-change syscall_arch.go.tmp syscall_arch.go $(STAMP) $@