在Linux中访问另一个进程虚拟内存（调试）

Z时代
2024-01-10
分类：问答

gdb如何在Linux上访问另一个进程虚拟内存？全部通过/ proc完成吗？

回答：

gdb如何在Linux上访问另一个进程虚拟内存？全部通过/ proc完成吗？

：

1）如字节数来读取比更少3 * sizeof

(long)或文件系统/proc不可用或从读取/proc/PID/mem不成功则ptrace使用具有PTRACE_PEEKTEXT读取数据。

这些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（long）并且/proc可用，则使用pread64或（lseek()和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;
}