From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Message-ID: <18206.32904.672941.222334@cargo.ozlabs.ibm.com> Date: Wed, 24 Oct 2007 09:15:20 +1000 From: Paul Mackerras To: Yuri Tikhonov Subject: Re: [PATCH] ppc44x: support for 256K PAGE_SIZE In-Reply-To: <200710222012.20316.yur@emcraft.com> References: <200710181108.19413.yur@emcraft.com> <18199.60025.563689.10810@cargo.ozlabs.ibm.com> <200710222012.20316.yur@emcraft.com> Cc: linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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.