Re: [PATCH] ppc44x: support for 256K PAGE_SIZE

[Paul Mackerras <paulus@samba.org>]

Yuri Tikhonov writes:

>  No it isn't the violation.
> 
>  As stated in "System V ABI. PowerPC processor supplement"
> (on which the "Linux Standard Base Core Specification for PPC32"
> is based): " ... Virtual addresses and file offsets for the PowerPC processor family 
> segments are congruent modulo 64 Kbytes (0x10000) or larger powers of 2...".

I'm afraid it is a violation.

In the "Operating System Interface" chapter, "Page Size" section (page
3-23 in the copy I have), it says: "Currently, the only valid hardware
page size for the PowerPC Architecture is 4096 bytes (4 Kbytes), but
this ABI allows the underlying operating system to cluster pages into
logical power-of-two page sizes up to 65536 bytes (64 Kbytes)."

The section you quoted says that ELF binaries may use a larger
congruency, not that the OS may use a larger page size.  In fact the
largest page size that the OS may use is the *smallest* congruency
that ELF binaries may use.

Of course, nothing says that you can't use kernels and binaries that
are not SVR4-compliant on your own machines.  But not being
SVR4-compliant certainly limits their general usefulness.

Paul.