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Source file src/runtime/mem_bsd.go

Documentation: runtime

  // Copyright 2010 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 dragonfly freebsd nacl netbsd openbsd solaris
  
  package runtime
  
  import (
  	"runtime/internal/sys"
  	"unsafe"
  )
  
  // Don't split the stack as this function may be invoked without a valid G,
  // which prevents us from allocating more stack.
  //go:nosplit
  func sysAlloc(n uintptr, sysStat *uint64) unsafe.Pointer {
  	v := mmap(nil, n, _PROT_READ|_PROT_WRITE, _MAP_ANON|_MAP_PRIVATE, -1, 0)
  	if uintptr(v) < 4096 {
  		return nil
  	}
  	mSysStatInc(sysStat, n)
  	return v
  }
  
  func sysUnused(v unsafe.Pointer, n uintptr) {
  	madvise(v, n, _MADV_FREE)
  }
  
  func sysUsed(v unsafe.Pointer, n uintptr) {
  }
  
  // Don't split the stack as this function may be invoked without a valid G,
  // which prevents us from allocating more stack.
  //go:nosplit
  func sysFree(v unsafe.Pointer, n uintptr, sysStat *uint64) {
  	mSysStatDec(sysStat, n)
  	munmap(v, n)
  }
  
  func sysFault(v unsafe.Pointer, n uintptr) {
  	mmap(v, n, _PROT_NONE, _MAP_ANON|_MAP_PRIVATE|_MAP_FIXED, -1, 0)
  }
  
  func sysReserve(v unsafe.Pointer, n uintptr, reserved *bool) unsafe.Pointer {
  	// On 64-bit, people with ulimit -v set complain if we reserve too
  	// much address space. Instead, assume that the reservation is okay
  	// and check the assumption in SysMap.
  	if sys.PtrSize == 8 && uint64(n) > 1<<32 || sys.GoosNacl != 0 {
  		*reserved = false
  		return v
  	}
  
  	p := mmap(v, n, _PROT_NONE, _MAP_ANON|_MAP_PRIVATE, -1, 0)
  	if uintptr(p) < 4096 {
  		return nil
  	}
  	*reserved = true
  	return p
  }
  
  const _sunosEAGAIN = 11
  const _ENOMEM = 12
  
  func sysMap(v unsafe.Pointer, n uintptr, reserved bool, sysStat *uint64) {
  	mSysStatInc(sysStat, n)
  
  	// On 64-bit, we don't actually have v reserved, so tread carefully.
  	if !reserved {
  		flags := int32(_MAP_ANON | _MAP_PRIVATE)
  		if GOOS == "dragonfly" {
  			// TODO(jsing): For some reason DragonFly seems to return
  			// memory at a different address than we requested, even when
  			// there should be no reason for it to do so. This can be
  			// avoided by using MAP_FIXED, but I'm not sure we should need
  			// to do this - we do not on other platforms.
  			flags |= _MAP_FIXED
  		}
  		p := mmap(v, n, _PROT_READ|_PROT_WRITE, flags, -1, 0)
  		if uintptr(p) == _ENOMEM || (GOOS == "solaris" && uintptr(p) == _sunosEAGAIN) {
  			throw("runtime: out of memory")
  		}
  		if p != v {
  			print("runtime: address space conflict: map(", v, ") = ", p, "\n")
  			throw("runtime: address space conflict")
  		}
  		return
  	}
  
  	p := mmap(v, n, _PROT_READ|_PROT_WRITE, _MAP_ANON|_MAP_FIXED|_MAP_PRIVATE, -1, 0)
  	if uintptr(p) == _ENOMEM || (GOOS == "solaris" && uintptr(p) == _sunosEAGAIN) {
  		throw("runtime: out of memory")
  	}
  	if p != v {
  		throw("runtime: cannot map pages in arena address space")
  	}
  }
  

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