unix: defer Getpagesize() to runtime

In general, page size is not a function of the archetecture. This was
addressed in the Go standard library here:
https://go-review.googlesource.com/25051

This change simply defers to the standard library "syscall" package,
which in turn defers to the runtime. This helps in addressing golang/go#10180 and
also fixes a bug on ppc64.

Currently, we return 65536 as the page size on ppc64, but the kernel
supports 4k and 64k sizes, see here:
http://elixir.free-electrons.com/linux/v4.13/source/arch/powerpc/include/asm/page.h#L24

Now that various page size calculations are not needed, various
components are now dead code and can also be removed. This CL reverts:
https://go-review.googlesource.com/14483
and part of:
https://go-review.googlesource.com/30755

Change-Id: I9d7a2d96359054e0dca9c985b026c8072b2eeaf3
Reviewed-on: https://go-review.googlesource.com/62111Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

unix/linux/types.go

@@ -535,10 +535,6 @@ const RNDGETENTCNT = C.RNDGETENTCNT
 
 const PERF_IOC_FLAG_GROUP = C.PERF_IOC_FLAG_GROUP
 
-// sysconf information
-
-const _SC_PAGESIZE = C._SC_PAGESIZE
-
 // Terminal handling
 
 type Termios C.termios_t

unix/gccgo_linux_sparc64.go → unix/pagesize_unix.go

-// Copyright 2016 The Go Authors.  All rights reserved.
+// Copyright 2017 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build gccgo,linux,sparc64
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+
+// For Unix, get the pagesize from the runtime.
 
 package unix
 
 import "syscall"
 
-//extern sysconf
-func realSysconf(name int) int64
-
-func sysconf(name int) (n int64, err syscall.Errno) {
-	r := realSysconf(name)
-	if r < 0 {
-		return 0, syscall.GetErrno()
-	}
-	return r, 0
+func Getpagesize() int {
+	return syscall.Getpagesize()
 }

unix/syscall_darwin_386.go

@@ -11,8 +11,6 @@ import (
 	"unsafe"
 )
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

unix/syscall_darwin_amd64.go

@@ -11,8 +11,6 @@ import (
 	"unsafe"
 )
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

unix/syscall_darwin_arm.go

@@ -9,8 +9,6 @@ import (
 	"unsafe"
 )
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

unix/syscall_darwin_arm64.go

@@ -11,8 +11,6 @@ import (
 	"unsafe"
 )
 
-func Getpagesize() int { return 16384 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

unix/syscall_dragonfly_amd64.go

@@ -11,8 +11,6 @@ import (
 	"unsafe"
 )
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

unix/syscall_freebsd_386.go

@@ -11,8 +11,6 @@ import (
 	"unsafe"
 )
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

unix/syscall_freebsd_amd64.go

@@ -11,8 +11,6 @@ import (
 	"unsafe"
 )
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

unix/syscall_freebsd_arm.go

@@ -11,8 +11,6 @@ import (
 	"unsafe"
 )
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return ts.Sec*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

unix/syscall_linux_386.go

@@ -14,8 +14,6 @@ import (
 	"unsafe"
 )
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

unix/syscall_linux_amd64.go

@@ -69,8 +69,6 @@ func Gettimeofday(tv *Timeval) (err error) {
 	return nil
 }
 
-func Getpagesize() int { return 4096 }
-
 func Time(t *Time_t) (tt Time_t, err error) {
 	var tv Timeval
 	errno := gettimeofday(&tv)

unix/syscall_linux_arm.go

@@ -11,8 +11,6 @@ import (
 	"unsafe"
 )
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

unix/syscall_linux_arm64.go

@@ -66,8 +66,6 @@ func Lstat(path string, stat *Stat_t) (err error) {
 //sys	sendmsg(s int, msg *Msghdr, flags int) (n int, err error)
 //sys	mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error)
 
-func Getpagesize() int { return 65536 }
-
 //sysnb	Gettimeofday(tv *Timeval) (err error)
 
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }

unix/syscall_linux_mips64x.go

@@ -55,8 +55,6 @@ package unix
 //sys	sendmsg(s int, msg *Msghdr, flags int) (n int, err error)
 //sys	mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error)
 
-func Getpagesize() int { return 65536 }
-
 //sysnb	Gettimeofday(tv *Timeval) (err error)
 
 func Time(t *Time_t) (tt Time_t, err error) {

unix/syscall_linux_mipsx.go

@@ -235,5 +235,3 @@ func Poll(fds []PollFd, timeout int) (n int, err error) {
 	}
 	return poll(&fds[0], len(fds), timeout)
 }
-
-func Getpagesize() int { return 4096 }

unix/syscall_linux_ppc64x.go

@@ -61,8 +61,6 @@ package unix
 //sys	sendmsg(s int, msg *Msghdr, flags int) (n int, err error)
 //sys	mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error)
 
-func Getpagesize() int { return 65536 }
-
 //sysnb	Gettimeofday(tv *Timeval) (err error)
 //sysnb	Time(t *Time_t) (tt Time_t, err error)
 

unix/syscall_linux_s390x.go

@@ -46,8 +46,6 @@ import (
 //sysnb	getgroups(n int, list *_Gid_t) (nn int, err error)
 //sysnb	setgroups(n int, list *_Gid_t) (err error)
 
-func Getpagesize() int { return 4096 }
-
 //sysnb	Gettimeofday(tv *Timeval) (err error)
 
 func Time(t *Time_t) (tt Time_t, err error) {

unix/syscall_linux_sparc64.go

@@ -6,11 +6,6 @@
 
 package unix
 
-import (
-	"sync/atomic"
-	"syscall"
-)
-
 //sys	EpollWait(epfd int, events []EpollEvent, msec int) (n int, err error)
 //sys	Dup2(oldfd int, newfd int) (err error)
 //sys	Fchown(fd int, uid int, gid int) (err error)
@@ -63,21 +58,6 @@ import (
 //sys	sendmsg(s int, msg *Msghdr, flags int) (n int, err error)
 //sys	mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error)
 
-func sysconf(name int) (n int64, err syscall.Errno)
-
-// pageSize caches the value of Getpagesize, since it can't change
-// once the system is booted.
-var pageSize int64 // accessed atomically
-
-func Getpagesize() int {
-	n := atomic.LoadInt64(&pageSize)
-	if n == 0 {
-		n, _ = sysconf(_SC_PAGESIZE)
-		atomic.StoreInt64(&pageSize, n)
-	}
-	return int(n)
-}
-
 func Ioperm(from int, num int, on int) (err error) {
 	return ENOSYS
 }

unix/syscall_netbsd_386.go

@@ -6,8 +6,6 @@
 
 package unix
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

unix/syscall_netbsd_amd64.go

@@ -6,8 +6,6 @@
 
 package unix
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

unix/syscall_netbsd_arm.go

@@ -6,8 +6,6 @@
 
 package unix
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

unix/syscall_openbsd_386.go

@@ -6,8 +6,6 @@
 
 package unix
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

unix/syscall_openbsd_amd64.go

@@ -6,8 +6,6 @@
 
 package unix
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

unix/syscall_openbsd_arm.go

@@ -6,10 +6,6 @@
 
 package unix
 
-import "syscall"
-
-func Getpagesize() int { return syscall.Getpagesize() }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

unix/syscall_solaris.go

@@ -13,7 +13,6 @@
 package unix
 
 import (
-	"sync/atomic"
 	"syscall"
 	"unsafe"
 )
@@ -699,18 +698,3 @@ func Mmap(fd int, offset int64, length int, prot int, flags int) (data []byte, e
 func Munmap(b []byte) (err error) {
 	return mapper.Munmap(b)
 }
-
-//sys	sysconf(name int) (n int64, err error)
-
-// pageSize caches the value of Getpagesize, since it can't change
-// once the system is booted.
-var pageSize int64 // accessed atomically
-
-func Getpagesize() int {
-	n := atomic.LoadInt64(&pageSize)
-	if n == 0 {
-		n, _ = sysconf(_SC_PAGESIZE)
-		atomic.StoreInt64(&pageSize, n)
-	}
-	return int(n)
-}

unix/types_solaris.go

@@ -256,10 +256,6 @@ type BpfTimeval C.struct_bpf_timeval
 
 type BpfHdr C.struct_bpf_hdr
 
-// sysconf information
-
-const _SC_PAGESIZE = C._SC_PAGESIZE
-
 // Terminal handling
 
 type Termios C.struct_termios

unix/zsyscall_solaris_amd64.go

@@ -129,7 +129,6 @@ import (
 //go:cgo_import_dynamic libc_getpeername getpeername "libsocket.so"
 //go:cgo_import_dynamic libc_setsockopt setsockopt "libsocket.so"
 //go:cgo_import_dynamic libc_recvfrom recvfrom "libsocket.so"
-//go:cgo_import_dynamic libc_sysconf sysconf "libc.so"
 
 //go:linkname procpipe libc_pipe
 //go:linkname procgetsockname libc_getsockname
@@ -250,7 +249,6 @@ import (
 //go:linkname procgetpeername libc_getpeername
 //go:linkname procsetsockopt libc_setsockopt
 //go:linkname procrecvfrom libc_recvfrom
-//go:linkname procsysconf libc_sysconf
 
 var (
 	procpipe,
@@ -371,8 +369,7 @@ var (
 	proc__xnet_getsockopt,
 	procgetpeername,
 	procsetsockopt,
-	procrecvfrom,
-	procsysconf syscallFunc
+	procrecvfrom syscallFunc
 )
 
 func pipe(p *[2]_C_int) (n int, err error) {
@@ -1589,12 +1586,3 @@ func recvfrom(fd int, p []byte, flags int, from *RawSockaddrAny, fromlen *_Sockl
 	}
 	return
 }
-
-func sysconf(name int) (n int64, err error) {
-	r0, _, e1 := sysvicall6(uintptr(unsafe.Pointer(&procsysconf)), 1, uintptr(name), 0, 0, 0, 0, 0)
-	n = int64(r0)
-	if e1 != 0 {
-		err = e1
-	}
-	return
-}

unix/ztypes_linux_386.go

@@ -673,8 +673,6 @@ const RNDGETENTCNT = 0x80045200
 
 const PERF_IOC_FLAG_GROUP = 0x1
 
-const _SC_PAGESIZE = 0x1e
-
 type Termios struct {
 	Iflag  uint32
 	Oflag  uint32

unix/ztypes_linux_amd64.go

@@ -691,8 +691,6 @@ const RNDGETENTCNT = 0x80045200
 
 const PERF_IOC_FLAG_GROUP = 0x1
 
-const _SC_PAGESIZE = 0x1e
-
 type Termios struct {
 	Iflag  uint32
 	Oflag  uint32

unix/ztypes_linux_arm.go

@@ -662,8 +662,6 @@ const RNDGETENTCNT = 0x80045200
 
 const PERF_IOC_FLAG_GROUP = 0x1
 
-const _SC_PAGESIZE = 0x1e
-
 type Termios struct {
 	Iflag  uint32
 	Oflag  uint32

unix/ztypes_linux_arm64.go

@@ -670,8 +670,6 @@ const RNDGETENTCNT = 0x80045200
 
 const PERF_IOC_FLAG_GROUP = 0x1
 
-const _SC_PAGESIZE = 0x1e
-
 type Termios struct {
 	Iflag  uint32
 	Oflag  uint32

unix/ztypes_linux_mips.go

@@ -667,8 +667,6 @@ const RNDGETENTCNT = 0x40045200
 
 const PERF_IOC_FLAG_GROUP = 0x1
 
-const _SC_PAGESIZE = 0x1e
-
 type Termios struct {
 	Iflag  uint32
 	Oflag  uint32

unix/ztypes_linux_mips64.go

@@ -672,8 +672,6 @@ const RNDGETENTCNT = 0x40045200
 
 const PERF_IOC_FLAG_GROUP = 0x1
 
-const _SC_PAGESIZE = 0x1e
-
 type Termios struct {
 	Iflag  uint32
 	Oflag  uint32

unix/ztypes_linux_mips64le.go

@@ -672,8 +672,6 @@ const RNDGETENTCNT = 0x40045200
 
 const PERF_IOC_FLAG_GROUP = 0x1
 
-const _SC_PAGESIZE = 0x1e
-
 type Termios struct {
 	Iflag  uint32
 	Oflag  uint32

unix/ztypes_linux_mipsle.go

@@ -667,8 +667,6 @@ const RNDGETENTCNT = 0x40045200
 
 const PERF_IOC_FLAG_GROUP = 0x1
 
-const _SC_PAGESIZE = 0x1e
-
 type Termios struct {
 	Iflag  uint32
 	Oflag  uint32

unix/ztypes_linux_ppc64.go

@@ -680,8 +680,6 @@ const RNDGETENTCNT = 0x40045200
 
 const PERF_IOC_FLAG_GROUP = 0x1
 
-const _SC_PAGESIZE = 0x1e
-
 type Termios struct {
 	Iflag  uint32
 	Oflag  uint32

unix/ztypes_linux_ppc64le.go

@@ -680,8 +680,6 @@ const RNDGETENTCNT = 0x40045200
 
 const PERF_IOC_FLAG_GROUP = 0x1
 
-const _SC_PAGESIZE = 0x1e
-
 type Termios struct {
 	Iflag  uint32
 	Oflag  uint32

unix/ztypes_linux_s390x.go

@@ -697,8 +697,6 @@ const RNDGETENTCNT = 0x80045200
 
 const PERF_IOC_FLAG_GROUP = 0x1
 
-const _SC_PAGESIZE = 0x1e
-
 type Termios struct {
 	Iflag  uint32
 	Oflag  uint32