modernc.org/memory@v1.8.0/mmap_illumos_amd64.go (about)

     1  // Copyright 2011 Evan Shaw. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE-MMAP-GO file.
     4  
     5  // Modifications (c) 2022 The Memory Authors.
     6  
     7  package memory // import "modernc.org/memory"
     8  
     9  import (
    10  	"os"
    11  	"syscall"
    12  	_ "unsafe"
    13  )
    14  
    15  const (
    16  	pageSizeLog = 20
    17  
    18  	// $ find /usr/include -name syscall.h
    19  	// /usr/include/sys/syscall.h
    20  	// $ grep -ni munmap /usr/include/sys/syscall.h
    21  	// 293:#define     SYS_munmap      117
    22  	// $ grep -ni mmap /usr/include/sys/syscall.h
    23  	// 291:#define	SYS_mmap	115
    24  	// 303:#define	SYS_mmapobj	127
    25  	// 442:#define	SYS_mmap64		214
    26  	// $
    27  	// $ uname -a
    28  	// SunOS omnios64 5.11 omnios-r151044-d3b715b9d1 i86pc i386 i86pc
    29  	// $
    30  	sys_MUNMAP = 117
    31  	sys_MMAP   = 214
    32  )
    33  
    34  var (
    35  	osPageMask = osPageSize - 1
    36  	osPageSize = os.Getpagesize()
    37  )
    38  
    39  //go:linkname mmapSyscall syscall.mmap
    40  func mmapSyscall(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error)
    41  
    42  func unmap(addr uintptr, size int) error {
    43  	_, _, errno := syscall.Syscall(sys_MUNMAP, addr, uintptr(size), 0)
    44  	if errno != 0 {
    45  		return errno
    46  	}
    47  
    48  	return nil
    49  }
    50  
    51  // pageSize aligned.
    52  func mmap(size int) (uintptr, int, error) {
    53  	size = roundup(size, osPageSize)
    54  	// The actual mmap syscall varies by architecture. mmapSyscall provides same
    55  	// functionality as the unexported funtion syscall.mmap and is declared in
    56  	// mmap_*_*.go and mmap_fallback.go. To add support for a new architecture,
    57  	// check function mmap in src/syscall/syscall_*_*.go or
    58  	// src/syscall/zsyscall_*_*.go in Go's source code.
    59  	p, err := mmapSyscall(0, uintptr(size+pageSize), syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_PRIVATE|syscall.MAP_ANON, -1, 0)
    60  	if err != nil {
    61  		return 0, 0, err
    62  	}
    63  
    64  	n := size + pageSize
    65  	if p&uintptr(osPageMask) != 0 {
    66  		panic("internal error")
    67  	}
    68  
    69  	mod := int(p) & pageMask
    70  	if mod != 0 {
    71  		m := pageSize - mod
    72  		if err := unmap(p, m); err != nil {
    73  			return 0, 0, err
    74  		}
    75  
    76  		n -= m
    77  		p += uintptr(m)
    78  	}
    79  
    80  	if p&uintptr(pageMask) != 0 {
    81  		panic("internal error")
    82  	}
    83  
    84  	if n-size != 0 {
    85  		if err := unmap(p+uintptr(size), n-size); err != nil {
    86  			return 0, 0, err
    87  		}
    88  	}
    89  
    90  	return p, size, nil
    91  }