On Tue, 14 Apr 2015 23:01:58 +0800, 慕冬亮 said:

> Hello Everyone:
>       What's the rule about heap management? Especially what's the function
> of do_brk?

Who says there's a "rule" about it? Some userspace heap managers don't
even *use* brk() or sbrk(), but instead use mmap() of an anonymous area.