github.com/cloudwego/frugal@v0.1.15/internal/loader/loader.go (about)

     1  /*
     2   * Copyright 2022 ByteDance Inc.
     3   *
     4   * Licensed under the Apache License, Version 2.0 (the "License");
     5   * you may not use this file except in compliance with the License.
     6   * You may obtain a copy of the License at
     7   *
     8   *     http://www.apache.org/licenses/LICENSE-2.0
     9   *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16  
    17  package loader
    18  
    19  import (
    20      `fmt`
    21      `os`
    22      `sync/atomic`
    23      `syscall`
    24      `unsafe`
    25  
    26      `github.com/cloudwego/frugal/internal/rt`
    27  )
    28  
    29  const (
    30      MAP_BASE = 0x7ff00000000
    31  )
    32  
    33  const (
    34      _AP = syscall.MAP_ANON  | syscall.MAP_PRIVATE
    35      _RX = syscall.PROT_READ | syscall.PROT_EXEC
    36      _RW = syscall.PROT_READ | syscall.PROT_WRITE
    37  )
    38  
    39  type (
    40      Loader   []byte
    41      Function unsafe.Pointer
    42  )
    43  
    44  var (
    45      FnCount  uint32
    46      LoadSize uintptr
    47      LoadBase uintptr = MAP_BASE
    48  )
    49  
    50  func mkptr(m uintptr) unsafe.Pointer {
    51      return *(*unsafe.Pointer)(unsafe.Pointer(&m))
    52  }
    53  
    54  func alignUp(n uintptr, a int) uintptr {
    55      return (n + uintptr(a) - 1) &^ (uintptr(a) - 1)
    56  }
    57  
    58  func (self Loader) Load(fn string, frame rt.Frame) (f Function) {
    59      var mm uintptr
    60      var er syscall.Errno
    61  
    62      /* align the size to pages */
    63      nf := uintptr(len(self))
    64      nb := alignUp(nf, os.Getpagesize())
    65      fp := atomic.AddUintptr(&LoadBase, nb) - nb
    66  
    67      /* allocate a block of memory */
    68      if mm, _, er = syscall.Syscall6(syscall.SYS_MMAP, fp, nb, _RW, _AP, 0, 0); er != 0 {
    69          panic(er)
    70      }
    71  
    72      /* copy code into the memory, and register the function */
    73      copy(rt.BytesFrom(mkptr(mm), len(self), int(nb)), self)
    74      registerFunction(fmt.Sprintf("(frugal).%s_%x", fn, mm), mm, nf, frame)
    75  
    76      /* make it executable */
    77      if _, _, err := syscall.Syscall(syscall.SYS_MPROTECT, mm, nb, _RX); err != 0 {
    78          panic(err)
    79      }
    80  
    81      /* record statistics */
    82      atomic.AddUint32(&FnCount, 1)
    83      atomic.AddUintptr(&LoadSize, nb)
    84      return Function(&mm)
    85  }