syscall.Getpagesize(): add test, implement for Linux and Windows

Author: dkegel-fastly

builder/musl.go

@@ -115,6 +115,7 @@ var Musl = Library{
 			"internal/libc.c",
 			"internal/syscall_ret.c",
 			"internal/vdso.c",
+			"legacy/*.c",
 			"malloc/*.c",
 			"mman/*.c",
 			"signal/*.c",

src/os/getpagesize_test.go

@@ -0,0 +1,17 @@
+//go:build windows || darwin || (linux && !baremetal)
+// +build windows darwin linux,!baremetal
+
+package os_test
+
+import (
+	"os"
+	"testing"
+)
+
+func TestGetpagesize(t *testing.T) {
+	pagesize := os.Getpagesize()
+	if pagesize == 0x1000 || pagesize == 0x4000 || pagesize == 0x10000 {
+		return
+	}
+	t.Errorf("os.Getpagesize() returns strange value %d", pagesize)
+}

src/os/types_anyos.go

@@ -7,6 +7,11 @@
 
 package os
 
+import "syscall"
+
+// Getpagesize returns the underlying system's memory page size.
+func Getpagesize() int { return syscall.Getpagesize() }
+
 func (fs *fileStat) Name() string { return fs.name }
 func (fs *fileStat) IsDir() bool  { return fs.Mode().IsDir() }
 

src/runtime/os_linux.go

@@ -40,3 +40,11 @@ func markGlobals() {
 	start = (start + unsafe.Alignof(uintptr(0)) - 1) &^ (unsafe.Alignof(uintptr(0)) - 1) // align on word boundary
 	markRoots(start, end)
 }
+
+//export getpagesize
+func libc_getpagesize() int
+
+//go:linkname syscall_Getpagesize syscall.Getpagesize
+func syscall_Getpagesize() int {
+	return libc_getpagesize()
+}

src/runtime/os_windows.go

@@ -90,3 +90,26 @@ func markGlobals() {
 		section = (*peSection)(unsafe.Pointer(uintptr(unsafe.Pointer(section)) + unsafe.Sizeof(peSection{})))
 	}
 }
+
+type systeminfo struct {
+	anon0                       [4]byte
+	dwpagesize                  uint32
+	lpminimumapplicationaddress *byte
+	lpmaximumapplicationaddress *byte
+	dwactiveprocessormask       uintptr
+	dwnumberofprocessors        uint32
+	dwprocessortype             uint32
+	dwallocationgranularity     uint32
+	wprocessorlevel             uint16
+	wprocessorrevision          uint16
+}
+
+//export GetSystemInfo
+func _GetSystemInfo(lpSystemInfo unsafe.Pointer)
+
+//go:linkname syscall_Getpagesize syscall.Getpagesize
+func syscall_Getpagesize() int {
+	var info systeminfo
+	_GetSystemInfo(unsafe.Pointer(&info))
+	return int(info.dwpagesize)
+}

src/syscall/syscall_libc.go

@@ -251,10 +251,6 @@ func Mprotect(b []byte, prot int) (err error) {
 	return
 }
 
-func Getpagesize() int {
-	return int(libc_getpagesize())
-}
-
 func Environ() []string {
 
 	// This function combines all the environment into a single allocation.
@@ -372,10 +368,6 @@ func libc_munmap(addr unsafe.Pointer, length uintptr) int32
 //export mprotect
 func libc_mprotect(addr unsafe.Pointer, len uintptr, prot int32) int32
 
-// int getpagesize();
-//export getpagesize
-func libc_getpagesize() int32
-
 // int chdir(const char *pathname, mode_t mode);
 //export chdir
 func libc_chdir(pathname *byte) int32

src/syscall/syscall_libc_darwin.go

@@ -267,6 +267,14 @@ func readdir_r(dir uintptr, entry *Dirent, result **Dirent) (err error) {
 	return
 }
 
+func Getpagesize() int {
+	return int(libc_getpagesize())
+}
+
 // int pipe(int32 *fds);
 //export pipe
 func libc_pipe(fds *int32) int32
+
+// int getpagesize();
+//export getpagesize
+func libc_getpagesize() int32

src/syscall/syscall_libc_nintendoswitch.go

@@ -67,3 +67,7 @@ func getErrno() error {
 func Pipe2(p []int, flags int) (err error) {
 	return ENOSYS // TODO
 }
+
+func Getpagesize() int {
+	return 4096 // TODO
+}

src/syscall/syscall_libc_wasi.go

@@ -296,6 +296,11 @@ func Pipe2(p []int, flags int) (err error) {
 	return ENOSYS // TODO
 }
 
+func Getpagesize() int {
+	// per upstream
+	return 65536
+}
+
 // int stat(const char *path, struct stat * buf);
 //export stat
 func libc_stat(pathname *byte, ptr unsafe.Pointer) int32

src/syscall/syscall_nonhosted.go

@@ -205,3 +205,9 @@ type Timeval struct {
 	Sec  int64
 	Usec int64
 }
+
+func Getpagesize() int {
+	// There is no right value to return here, but 4096 is a
+	// common assumption when pagesize is unknown
+	return 4096
+}