Syscalls.h

//
// Copyright (c) 2014-present, Facebook, Inc.
// All rights reserved.
//
// This source code is licensed under the University of Illinois/NCSA Open
// Source License found in the LICENSE file in the root directory of this
// source tree. An additional grant of patent rights can be found in the
// PATENTS file in the same directory.
//
 
#pragma once
 
#include <sys/mman.h>
 
namespace ds2 {
namespace Host {
namespace Linux {
namespace X86 {
namespace Syscalls {
 
namespace {
static uint8_t const gMmapCode[] = {
    0xb8, 0x00, 0x00, 0x00, 0x00, // 00: movl $sysno, %eax
    0x31, 0xdb,                   // 05: xorl %ebx, %ebx
    0xb9, 0x00, 0x00, 0x00, 0x00, // 07: movl $XXXXXXXX, %ecx
    0xba, 0x00, 0x00, 0x00, 0x00, // 0c: movl $XXXXXXXX, %edx
    0xbe, 0x00, 0x00, 0x00, 0x00, // 11: movl $XXXXXXXX, %esi
    0xbf, 0xff, 0xff, 0xff, 0xff, // 16: movl $-1, %edi
    0x31, 0xed,                   // 1b: xorl %ebp, %ebp
    0xcd, 0x80,                   // 1d: int  $0x80
    0xcc                          // 1f: int3
};
 
static uint8_t const gMunmapCode[] = {
    0xb8, 0x00, 0x00, 0x00, 0x00, // 00: movl $sysno, %eax
    0xbb, 0x00, 0x00, 0x00, 0x00, // 05: movl $XXXXXXXX, %ebx
    0xb9, 0x00, 0x00, 0x00, 0x00, // 0a: movl $XXXXXXXX, %ecx
    0xcd, 0x80,                   // 0f: int  $0x80
    0xcc                          // 10: int3
};
} // namespace
 
static inline void PrepareMmapCode(size_t size, int protection,
                                   ByteVector &codestr) {
  codestr.assign(&gMmapCode[0], &gMmapCode[sizeof(gMmapCode)]);
 
  uint8_t *code = &codestr[0];
  *reinterpret_cast<uint32_t *>(code + 0x01) = 192; // __NR_mmap2
  *reinterpret_cast<uint32_t *>(code + 0x08) = size;
  *reinterpret_cast<uint32_t *>(code + 0x0d) = protection;
  *reinterpret_cast<uint32_t *>(code + 0x12) = MAP_ANON | MAP_PRIVATE;
}
 
static inline void PrepareMunmapCode(uint32_t address, size_t size,
                                     ByteVector &codestr) {
  codestr.assign(&gMunmapCode[0], &gMunmapCode[sizeof(gMunmapCode)]);
 
  uint8_t *code = &codestr[0];
  *reinterpret_cast<uint32_t *>(code + 0x01) = 91; // __NR_munmap
  *reinterpret_cast<uint32_t *>(code + 0x06) = address;
  *reinterpret_cast<uint32_t *>(code + 0x0b) = size;
}
} // namespace Syscalls
} // namespace X86
} // namespace Linux
} // namespace Host
} // namespace ds2