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在Linux中访问另一个进程虚拟内存(调试)

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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?


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2020-06-07

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小编典典

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?

在Linux上读取内存

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()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上写内存

1)ptracePTRACE_POKETEXT或一起PTRACE_POKEDATA使用。


至于第二个问题:

在哪里可以找到有关…设置硬件观察点的信息

gdb,内部观察点:s
http://sourceware.org/gdb/wiki/Internals%20Watchpoints

参考:

2020-06-07