unix: add Uname on dragonfly

The Utsname members are only 32 bytes on Dragonfly and the syscall
returns ENOMEM in case the value is longer than that. Like uname(3)
on Dragonfly, handle this case gracefully and just truncate the
value.

Change-Id: If617af1b6831cff6d4245f498dad9f264b8fd118
Reviewed-on: https://go-review.googlesource.com/82155
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/syscall_dragonfly.go

@@ -169,6 +169,69 @@ func IoctlGetTermios(fd int, req uint) (*Termios, error) {
 	return &value, err
 }
 
+func sysctlUname(mib []_C_int, old *byte, oldlen *uintptr) error {
+	err := sysctl(mib, old, oldlen, nil, 0)
+	if err != nil {
+		// Utsname members on Dragonfly are only 32 bytes and
+		// the syscall returns ENOMEM in case the actual value
+		// is longer.
+		if err == ENOMEM {
+			err = nil
+		}
+	}
+	return err
+}
+
+func Uname(uname *Utsname) error {
+	mib := []_C_int{CTL_KERN, KERN_OSTYPE}
+	n := unsafe.Sizeof(uname.Sysname)
+	if err := sysctlUname(mib, &uname.Sysname[0], &n); err != nil {
+		return err
+	}
+	uname.Sysname[unsafe.Sizeof(uname.Sysname)-1] = 0
+
+	mib = []_C_int{CTL_KERN, KERN_HOSTNAME}
+	n = unsafe.Sizeof(uname.Nodename)
+	if err := sysctlUname(mib, &uname.Nodename[0], &n); err != nil {
+		return err
+	}
+	uname.Nodename[unsafe.Sizeof(uname.Nodename)-1] = 0
+
+	mib = []_C_int{CTL_KERN, KERN_OSRELEASE}
+	n = unsafe.Sizeof(uname.Release)
+	if err := sysctlUname(mib, &uname.Release[0], &n); err != nil {
+		return err
+	}
+	uname.Release[unsafe.Sizeof(uname.Release)-1] = 0
+
+	mib = []_C_int{CTL_KERN, KERN_VERSION}
+	n = unsafe.Sizeof(uname.Version)
+	if err := sysctlUname(mib, &uname.Version[0], &n); err != nil {
+		return err
+	}
+
+	// The version might have newlines or tabs in it, convert them to
+	// spaces.
+	for i, b := range uname.Version {
+		if b == '\n' || b == '\t' {
+			if i == len(uname.Version)-1 {
+				uname.Version[i] = 0
+			} else {
+				uname.Version[i] = ' '
+			}
+		}
+	}
+
+	mib = []_C_int{CTL_HW, HW_MACHINE}
+	n = unsafe.Sizeof(uname.Machine)
+	if err := sysctlUname(mib, &uname.Machine[0], &n); err != nil {
+		return err
+	}
+	uname.Machine[unsafe.Sizeof(uname.Machine)-1] = 0
+
+	return nil
+}
+
 /*
  * Exposed directly
  */

unix/types_dragonfly.go

@@ -35,6 +35,7 @@ package unix
 #include <sys/time.h>
 #include <sys/types.h>
 #include <sys/un.h>
+#include <sys/utsname.h>
 #include <sys/wait.h>
 #include <net/bpf.h>
 #include <net/if.h>
@@ -267,3 +268,7 @@ const (
 	POLLWRBAND = C.POLLWRBAND
 	POLLWRNORM = C.POLLWRNORM
 )
+
+// Uname
+
+type Utsname C.struct_utsname

unix/zerrors_dragonfly_amd64.go

@@ -168,6 +168,8 @@ const (
 	CSTOP                             = 0x13
 	CSTOPB                            = 0x400
 	CSUSP                             = 0x1a
+	CTL_HW                            = 0x6
+	CTL_KERN                          = 0x1
 	CTL_MAXNAME                       = 0xc
 	CTL_NET                           = 0x4
 	DLT_A429                          = 0xb8
@@ -353,6 +355,7 @@ const (
 	F_UNLCK                           = 0x2
 	F_WRLCK                           = 0x3
 	HUPCL                             = 0x4000
+	HW_MACHINE                        = 0x1
 	ICANON                            = 0x100
 	ICMP6_FILTER                      = 0x12
 	ICRNL                             = 0x100
@@ -835,6 +838,10 @@ const (
 	IXANY                             = 0x800
 	IXOFF                             = 0x400
 	IXON                              = 0x200
+	KERN_HOSTNAME                     = 0xa
+	KERN_OSRELEASE                    = 0x2
+	KERN_OSTYPE                       = 0x1
+	KERN_VERSION                      = 0x4
 	LOCK_EX                           = 0x2
 	LOCK_NB                           = 0x4
 	LOCK_SH                           = 0x1

unix/ztypes_dragonfly_amd64.go

@@ -472,3 +472,11 @@ const (
 	POLLWRBAND = 0x100
 	POLLWRNORM = 0x4
 )
+
+type Utsname struct {
+	Sysname  [32]byte
+	Nodename [32]byte
+	Release  [32]byte
+	Version  [32]byte
+	Machine  [32]byte
+}