os: fix blockUntilWaitable on freebsd/{386,arm}

The previous fix was wrong because it had two misunderstandings on
freebsd32 calling convention like the following:
- 32-bit id1 implies that it is the upper half of 64-bit id, indeed it
  depends on machine endianness.
- 32-bit ARM calling convension doesn't conform to freebsd32_args,
  indeed it does.

This change fixes the bugs and makes blockUntilWaitable work correctly
on freebsd/{386,arm}.

Fixes #16064.

Change-Id: I820c6d01d59a43ac4f2ab381f757c03b14bca75e
Reviewed-on: https://go-review.googlesource.com/24064
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/os/wait_wait6.go b/src/os/wait_wait6.go
index 2f27feda8ddb1d36fc32e7032c41a2cb6be15678..7f4780ae2d0ab8a9622f7629b68d1e66ece0dae8 100644 (file)
--- a/src/os/wait_wait6.go
+++ b/src/os/wait_wait6.go
@@ -18,25 +18,20 @@ const _P_PID = 0
 // It does not actually call p.Wait.
 func (p *Process) blockUntilWaitable() (bool, error) {
        var errno syscall.Errno
+       // The arguments on 32-bit FreeBSD look like the following:
+       // - freebsd32_wait6_args{ idtype, id1, id2, status, options, wrusage, info } or
+       // - freebsd32_wait6_args{ idtype, pad, id1, id2, status, options, wrusage, info } when PAD64_REQUIRED=1 on ARM, MIPS or PowerPC
        if runtime.GOARCH == "386" {
-               // The arguments on 32-bit FreeBSD except ARM look
-               // like the following:
-               // - freebsd32_wait6_args{ idtype, id1, id2, status, options, wrusage, info } or
-               // - freebsd32_wait6_args{ idtype, pad, id1, id2, status, options, wrusage, info } when PAD64_REQUIRED=1 on MIPS or PowerPC
-               _, _, errno = syscall.Syscall9(syscall.SYS_WAIT6, _P_PID, 0, uintptr(p.Pid), 0, syscall.WEXITED|syscall.WNOWAIT, 0, 0, 0, 0)
+               _, _, errno = syscall.Syscall9(syscall.SYS_WAIT6, _P_PID, uintptr(p.Pid), 0, 0, syscall.WEXITED|syscall.WNOWAIT, 0, 0, 0, 0)
+       } else if runtime.GOARCH == "arm" {
+               _, _, errno = syscall.Syscall9(syscall.SYS_WAIT6, _P_PID, 0, uintptr(p.Pid), 0, 0, syscall.WEXITED|syscall.WNOWAIT, 0, 0, 0)
        } else {
                _, _, errno = syscall.Syscall6(syscall.SYS_WAIT6, _P_PID, uintptr(p.Pid), 0, syscall.WEXITED|syscall.WNOWAIT, 0, 0)
        }
        if errno != 0 {
                // The wait6 system call is supported only on FreeBSD
                // 9.3 and above, so it may return an ENOSYS error.
-               // Also the system call may return an ECHILD error
-               // when the child process has not finished the
-               // transformation using execve system call.
-               // In both cases, we just leave the care of child
-               // process to the following wait4 system call in
-               // Process.wait.
-               if errno == syscall.ENOSYS || errno == syscall.ECHILD {
+               if errno == syscall.ENOSYS {
                        return false, nil
                }
                return false, NewSyscallError("wait6", errno)