linux - 使用hexdump检查/dev/mem时，为什么有些地址不见了？

Question

这是我使用的命令:

sudo hexdump -C/dev/mem |少

它转储的部分结果:

00000070  53 ff 00 f0 a4 f0 00 f0  c7 ef 00 f0 e0 ba 00 c0  |S...............|
00000080  ef 27 00 f0 ef 27 00 f0  ef 27 00 f0 ef 27 00 f0  |.'...'...'...'..|
*
00000100  99 1b 32 e7 01 e4 00 f0  65 f0 00 f0 e0 be 00 c0  |..2.....e.......|
00000110  ef 27 00 f0 ef 27 00 f0  ef 27 00 f0 ef 27 00 f0  |.'...'...'...'..|
*
00000180  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

有趣的是 [0x00000120, 0x0000017f] 中的地址被忽略为“*”而不是我想看到的值。

据我所知，这些部分是 protected ，不被阅读，但为什么呢？还是我遗漏了什么？

Answer 1

hexdump 正在抑制重复行以使输出更易于阅读。

来自“man hexdump”页面:

-v      Cause hexdump to display all input data.  Without the -v option,
        any number of groups of output lines, which would be identical to
        the immediately preceding group of output lines (except for the
        input offsets), are replaced with a line comprised of a single
        asterisk.