From mboxrd@z Thu Jan 1 00:00:00 1970 From: tomasz.figa@gmail.com (Tomasz Figa) Date: Thu, 10 Jan 2013 11:52:22 +0100 Subject: some question about usermode:kernel mode is not 2:2 or 1:3 In-Reply-To: References: Message-ID: <5478233.oiXe2QDsbJ@flatron> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi, On Thursday 10 of January 2013 18:39:25 loody wrote: > hi all: > There are some hw limitations on my platform. > 1. dram size is only 128MB. > 2. cpu dram physical address range only from 0x0 ~ 0x8000000(128MB) > that means my PAGE_OFFSET cannot set as 2G or 3G > > per above #1 and #2 limitation, I have to change PAGE_OFFSET = > 0x4000000(64MB) Kernel booting very well. > but it will fail on running init, the first usermode program. > > my question are: > A. I use codesourcety toolchain, is it possible this failure due to > toolchain not knowing the size limitation. > B. if A is correct, should I cross-compile own toolchain to link my own > kernel? You seem to confuse physical memory with virtual memory. Here's a nice article about virtual memory on Linux: http://linux-mm.org/VirtualMemory Best regards, Tomasz Figa