Fix mmap logic on MAP_FIXED

[bet4it]

Checklist

Which kind of PR do you create?

• This PR only contains minor fixes.
• This PR contains major feature update.
• This PR introduces a new function/api for Qiling Framework.

Coding convention?

• The new code conforms to Qiling Framework naming convention.
• The imports are arranged properly.
• Essential comments are added.
• The reference of the new code is pointed out.

Extra tests?

• No extra tests are needed for this PR.
• I have added enough tests for this PR.
• Tests will be added after some discussion and review.

Changelog?

• This PR doesn't need to update Changelog.
• Changelog will be updated after some proper review.
• Changelog has been updated in my PR.

Target branch?

• The target branch is dev branch.

One last thing

• I have read the contribution guide

---

If addr is NULL, then the kernel chooses the (page-aligned) address at which to create the mapping; this is the most portable method of creating a new mapping. If addr is not NULL, then the kernel takes it as a hint about where to place the mapping; on Linux, the kernel will pick a nearby page boundary (but always above or equal to the value specified by /proc/sys/vm/mmap_min_addr) and attempt to create the mapping there. If another mapping already exists there, the kernel picks a new address that may or may not depend on the hint. The address of the new mapping is returned as the result of the call.

If addr is not NULL, we need to map on this address even if MAP_FIXED is not set, except this address is already mapped.

[cla7aye15I4nd]

may be you can provide some test?

[bet4it]

I can't find any existing tests about mmap😅
And mmap is used in almost all programs, so we can test it base on the real usage of it.
I will send a PR of a realworld program which will trigger this bug lately. ( hope in this year😅 )

[xwings]

cool, waiting :)

[bet4it]

That will be another PR, hope this can be merged.

[xwings]

will you be able to solve the conflict?

[bet4it]

@xwings Done