Re: [linuxsh-dev] Different old_mmap behavior in 2.4.5 and 2.4.8

[David W. <dw...@in...>]

dr...@re... said:
>  Then fix the kernel.  The change is necessary and correct. 

I believe the change was made for cache aliasing reasons - on SH4 we have a 
virtually-indexed cache with 8KiB-worth of entries, and we avoid having 
alias problems by allowing only even pages to be mapped at even addresses, 
and odd pages at odd addresses.

I haven't checked whether the kernel will make the offending mmap fail if 
you specify MAP_FIXED, or whether it'll fall back into cache-flushing mode, 
map the range uncached or deal with it some other way to give you the 
address you asked for. But surely unless you specify MAP_FIXED, the kernel 
is perfectly entitled to fix up the address to ensure cache sanity?

Why was it necessary to remove MAP_FIXED?

--
dwmw2