在Linux中访问另一个进程虚拟内存(调试)

Question

gdb如何在Linux上访问另一个进程虚拟内存？这一切都是通过/ proc完成的吗？

Answer 1

gdb如何在Linux上访问另一个进程虚拟内存？这一切都是通过/ proc完成的吗？

在Linux上读取内存:

1)如果要读取的字节数小于3 * sizeof (long)或者文件系统/proc不可用或读取/proc/PID/mem不成功则ptrace用于PTRACE_PEEKTEXT读取数据.

以下是函数中的这些条件linux_proc_xfer_partial():

  /* Don't bother for one word.  */
  if (len < 3 * sizeof (long))
    return 0;

  /* We could keep this file open and cache it - possibly one per
     thread.  That requires some juggling, but is even faster.  */
  xsnprintf (filename, sizeof filename, "/proc/%d/mem",
         ptid_get_pid (inferior_ptid));
  fd = gdb_open_cloexec (filename, O_RDONLY | O_LARGEFILE, 0);
  if (fd == -1)
    return 0;

2)如果要读取的字节数大于或等于3*sizeof(长)并且/proc可用,则pread64(lseek()或read()使用:

static LONGEST
linux_proc_xfer_partial (struct target_ops *ops, enum target_object object,
             const char *annex, gdb_byte *readbuf,
             const gdb_byte *writebuf,
             ULONGEST offset, LONGEST len)
{
  .....

  /* If pread64 is available, use it.  It's faster if the kernel
     supports it (only one syscall), and it's 64-bit safe even on
     32-bit platforms (for instance, SPARC debugging a SPARC64
     application).  */
#ifdef HAVE_PREAD64
  if (pread64 (fd, readbuf, len, offset) != len)
#else
  if (lseek (fd, offset, SEEK_SET) == -1 || read (fd, readbuf, len) != len)
#endif
    ret = 0;
  else
    ret = len;

  close (fd);
  return ret;
}

在Linux上用于写入内存:

1)ptrace使用PTRACE_POKETEXT或PTRACE_POKEDATA使用.

至于你的第二个问题:

我在哪里可以找到有关...设置硬件观察点的信息

gdb,Internals Watchpoint:s http://sourceware.org/gdb/wiki/Internals%20Watchpoints

参考:

• http://linux.die.net/man/2/ptrace
• http://www.alexonlinux.com/how-debugger-works