Hi! > > If we had a time machine, the right set of flags would be: > > > > - MAP_FIXED: don't treat addr as a hint, fail if addr is not free > > - MAP_REPLACE: replace an existing mapping (or force or clobber) > > Actually, if we had a time machine... would we even provide > MAP_REPLACE functionality? I did a bit of archeology just beacause we can and since there is a git repository of the unix history [1]. The first version of mmap() seems to appear in BSD-4_2-Snapshot there was no MAP_FIXED flag and the addr is expected to be used for the mapping. At least that is what manual seems to say, the kernel code is not written at this point. This seems to correspond to a time when Berkley students were busy rewriting UNIX kernel to take advantage of the VAX's virtual memory. The MAP_FIXED arrived to the manual shortly after, probably someone figured out that passing an address to the call does not make much sense in most of the cases. The first actual implementation that supports MAP_FIXED appeared in the BSD-4_3_Reno-Snapshot and already includes the replace behavior. The original purpose seems to be replacing mappings in the implementation of the execve() call. So the answer would probably be yes but it would probably made sense to keep it as kernel internal flag. And BTW it looks like HPUX got it right before it was changed to follow POSIX. There seems to be HPUX compatibility code in the early BSD codebase that contains both HPUXMAP_FIXED and HPUXMAP_REPLACE. [1] https://github.com/dspinellis/unix-history-repo -- Cyril Hrubis chrubis@xxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
