Messages in this thread | | | Date | Thu, 03 May 2007 23:30:53 +1000 | From | Greg Ungerer <> | Subject | Re: [PATCH]: linux-2.6.21-uc0 (MMU-less updates) |
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Robin Getz wrote: > On Thu 3 May 2007 07:03, Greg Ungerer pondered: >> Robin Getz wrote: >>> On Wed 2 May 2007 07:32, Greg Ungerer pondered: >>>> Robin Getz wrote: >>>>> I was trying to understand why we don't want to do the same checking on >>>>> noMMU? >>>> The problem is on systems that have RAM mapped at high physical >>>> addresses. TASK_SIZE may well be a numerically smaller number >>>> than the address range that RAM sits in. So this test fails when >>>> it shouldn't. >>> So, then this is a problem only on one or two architectures, not all >>> noMMU platforms? >> Its not an architecture problem. It can effect any board that >> has RAM mapped at a large numerical addresses (larger than TASK_SIZE). >> So it can effect any non-MMU platform. > > Depending on how TASK_SIZE is defined - it looks like everyone else forces it > to end of memory, except 68k[nommu]. > > asm-arm/memory.h:#define TASK_SIZE (CONFIG_DRAM_SIZE) > asm-blackfin/processor.h:#define TASK_SIZE (memory_end) > asm-frv/mem-layout.h:#define TASK_SIZE __UL(0xFFFFFFFFUL) > > asm-m68k/processor.h:#define TASK_SIZE (0xF0000000UL) > asm-m68k/processor.h:#define TASK_SIZE (0x0E000000) > asm-m68k/processor.h:#define TASK_SIZE (0x0E000000UL) > asm-m68knommu/processor.h:#define TASK_SIZE (0xF0000000UL)
Probably too:
asm-sh/processor.h:#define TASK_SIZE 0x7c000000UL
which has some parts with MMU.
There have been others out of tree that have it like this to.
> I'm happy to learn we are doing something wrong, but I think that we just > copied the arm/frv setup.
That is one way to handle it. Have you followed all the other uses of TASK_SIZE and verified it is not a problem?
Regards Greg
------------------------------------------------------------------------ Greg Ungerer -- Chief Software Dude EMAIL: gerg@snapgear.com SnapGear -- a Secure Computing Company PHONE: +61 7 3435 2888 825 Stanley St, FAX: +61 7 3891 3630 Woolloongabba, QLD, 4102, Australia WEB: http://www.SnapGear.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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