syscall: wrong TCGETS value on ppc64le

[zhsj]

What version of Go are you using (go version)?

go version go1.9 linux/ppc64le

Does this issue reproduce with the latest release?

yes, with go1.9

What operating system and processor architecture are you using (go env)?

GOARCH="ppc64le"
GOBIN=""
GOEXE=""
GOHOSTARCH="ppc64le"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/debian/go"
GORACE=""
GOROOT="/usr/lib/go-1.9"
GOTOOLDIR="/usr/lib/go-1.9/pkg/tool/linux_ppc64le"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build617591770=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"

What did you do?

I meet strange output when I use github.com/mattn/go-isatty, the following snippet explains.

/*
#include <unistd.h>
*/
import "C"
import "unsafe"
import "syscall"
import "golang.org/x/sys/unix"

func main() {
        C.isatty(C.int(0))
        var termios syscall.Termios
        syscall.Syscall6(syscall.SYS_IOCTL, 0, syscall.TCGETS, uintptr(unsafe.Pointer(&termios)), 0, 0, 0)
        unix.Syscall6(unix.SYS_IOCTL, 0, unix.TCGETS, uintptr(unsafe.Pointer(&termios)), 0, 0, 0)
        syscall.Syscall6(syscall.SYS_IOCTL, 0, 0x402c7413, uintptr(unsafe.Pointer(&termios)), 0, 0, 0)
}

run strace to see the real syscall.

strace ./isatty 2>&1 |grep -i ioc
ioctl(0, TCGETS, {B38400 opost isig icanon echo ...}) = 0
ioctl(0, _IOC(_IOC_READ, 0x74, 0x13, 0x3c), 0xc42004fef8) = -1 ENOTTY (Inappropriate ioctl for device)
ioctl(0, TCGETS, {B38400 opost isig icanon echo ...}) = 0
ioctl(0, TCGETS, {B38400 opost isig icanon echo ...}) = 0

The syscall.TCGETS is wrong and should be 0x402c7413(the one in sys/unix)

[zhsj]

And I get same result when I use gccgo

go version go1.8.3 gccgo (Debian 20170830-1) 8.0.0 20170830 (experimental) [trunk revision 251527] linux/ppc64le

[ianlancetaylor]

This seems the same as #19560, but that issue was closed by a seemingly irrelevant change. I'm not sure what's going on here; I thought that in #19560 we agreed that we should change the values in the syscall package.

CC @laboger

[zhsj]

@ianlancetaylor thanks for the reference issue. I didn't find it since I forgot to search on the closed issues.
After reading the discussion, I think I need to raise the issue on github.com/mattn/go-isatty too, since it's using std syscall, regarding the std syscall should be fixed or not.

[laboger]

My understanding is that x/sys should be used wherever possible, but there are still cases where std syscall has to be used because not everything has been migrated over. We opened #19697 for this question. The documentation in the file syscall/syscall.go was updated to indicate what is missing from the migration. I think at the time we had hit this problem, x/sys was undergoing major changes and @bradfitz asked us to wait for that to be finished before making any changes.

I think Signal and Errno could be migrated, but I don't think SysProcAttr could be for compatibility reasons.

@ceseo

[ianlancetaylor]

@laboger I think the question in this specific issue is: why not just correct the value of TCGETS in the syscall package? As discussed in #19560 correcting the value of syscall.TCGETS would be OK per syscall package rules.

[gopherbot]

Change https://golang.org/cl/66510 mentions this issue: syscall: correct TCGETS/TCSETS values on ppc64/ppc64le