syscall: make Getpagesize return page size from runtime

syscall.Getpagesize currently returns hard-coded page sizes on all
architectures (some of which are probably always wrong, and some of
which are definitely not always right). The runtime now has this
information, queried from the OS during runtime init, so make
syscall.Getpagesize return the page size that the runtime knows.

Updates #10180.

Change-Id: I4daa6fbc61a2193eb8fa9e7878960971205ac346
Reviewed-on: https://go-review.googlesource.com/25051
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/runtime.go

@@ -52,5 +52,8 @@ var argslice []string
 //go:linkname syscall_runtime_envs syscall.runtime_envs
 func syscall_runtime_envs() []string { return append([]string{}, envs...) }
 
+//go:linkname syscall_Getpagesize syscall.Getpagesize
+func syscall_Getpagesize() int { return int(physPageSize) }
+
 //go:linkname os_runtime_args os.runtime_args
 func os_runtime_args() []string { return append([]string{}, argslice...) }

src/syscall/syscall.go

@@ -95,6 +95,10 @@ func (tv *Timeval) Nano() int64 {
 	return int64(tv.Sec)*1e9 + int64(tv.Usec)*1000
 }
 
+// Getpagesize is provided by the runtime.
+
+func Getpagesize() int
+
 // use is a no-op, but the compiler cannot see that it is.
 // Calling use(p) ensures that p is kept live until that point.
 // This was needed until Go 1.6 to call syscall.Syscall correctly.

src/syscall/syscall_darwin_386.go

@@ -6,8 +6,6 @@ package syscall
 
 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) {

src/syscall/syscall_darwin_amd64.go

@@ -6,8 +6,6 @@ package syscall
 
 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) {

src/syscall/syscall_darwin_arm.go

@@ -6,8 +6,6 @@ package syscall
 
 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) {

src/syscall/syscall_darwin_arm64.go

@@ -6,8 +6,6 @@ package syscall
 
 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) {

src/syscall/syscall_dragonfly_amd64.go

@@ -6,8 +6,6 @@ package syscall
 
 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) {

src/syscall/syscall_freebsd_386.go

@@ -6,8 +6,6 @@ package syscall
 
 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) {

src/syscall/syscall_freebsd_amd64.go

@@ -6,8 +6,6 @@ package syscall
 
 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) {

src/syscall/syscall_freebsd_arm.go

@@ -6,8 +6,6 @@ package syscall
 
 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) {

src/syscall/syscall_linux_386.go

@@ -14,8 +14,6 @@ const (
 	_SYS_getdents = SYS_GETDENTS64
 )
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

src/syscall/syscall_linux_amd64.go

@@ -72,8 +72,6 @@ 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)

src/syscall/syscall_linux_arm.go

@@ -11,8 +11,6 @@ const (
 	_SYS_getdents = SYS_GETDENTS64
 )
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

src/syscall/syscall_linux_arm64.go

@@ -68,8 +68,6 @@ 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)
 //sysnb	Time(t *Time_t) (tt Time_t, err error)
 

src/syscall/syscall_linux_mips64x.go

@@ -65,8 +65,6 @@ const (
 //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) {

src/syscall/syscall_linux_ppc64x.go

@@ -64,8 +64,6 @@ const (
 //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)
 

src/syscall/syscall_linux_s390x.go

@@ -44,8 +44,6 @@ const (
 //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) {

src/syscall/syscall_nacl.go

@@ -292,7 +292,6 @@ func Getegid() int                      { return 1 }
 func Geteuid() int                      { return 1 }
 func Getgid() int                       { return 1 }
 func Getgroups() ([]int, error)         { return []int{1}, nil }
-func Getpagesize() int                  { return 65536 }
 func Getppid() int                      { return 2 }
 func Getpid() int                       { return 3 }
 func Gettimeofday(tv *Timeval) error    { return ENOSYS }

src/syscall/syscall_netbsd_386.go

@@ -4,8 +4,6 @@
 
 package syscall
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

src/syscall/syscall_netbsd_amd64.go

@@ -4,8 +4,6 @@
 
 package syscall
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

src/syscall/syscall_netbsd_arm.go

@@ -4,8 +4,6 @@
 
 package syscall
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

src/syscall/syscall_openbsd_386.go

@@ -4,8 +4,6 @@
 
 package syscall
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

src/syscall/syscall_openbsd_amd64.go

@@ -4,8 +4,6 @@
 
 package syscall
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

src/syscall/syscall_openbsd_arm.go

@@ -4,8 +4,6 @@
 
 package syscall
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

src/syscall/syscall_plan9.go

@@ -305,8 +305,6 @@ func Gettimeofday(tv *Timeval) error {
 	return nil
 }
 
-func Getpagesize() int { return 0x1000 }
-
 func Getegid() (egid int) { return -1 }
 func Geteuid() (euid int) { return -1 }
 func Getgid() (gid int)   { return -1 }

src/syscall/syscall_solaris_amd64.go

@@ -4,8 +4,6 @@
 
 package syscall
 
-func Getpagesize() int { return 4096 }
-
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {

src/syscall/syscall_windows.go

@@ -74,8 +74,6 @@ func UTF16PtrFromString(s string) (*uint16, error) {
 	return &a[0], nil
 }
 
-func Getpagesize() int { return 4096 }
-
 // Errno is the Windows error number.
 type Errno uintptr