Re: [PATCH]: linux-2.6.21-uc0 (MMU-less updates)

[Greg Ungerer <gerg@snapgear.com>]

Hi Robin,

Robin Getz wrote:
> On Wed 2 May 2007 01:23, Greg Ungerer pondered:
> > Hi All,
> >
> > An update of the uClinux (MMU-less) code against 2.6.21.
> > A lot of cleanups, and a few bug fixes.
> >
> > Ahead is more changes to finalize platform device support
> > for the new style ColdFire serial driver, and switching to
> > the generic irq code.
> >
> > http://www.uclinux.org/pub/uClinux/uClinux-2.6.x/linux-2.6.21-uc0.patch.gz
>
> Greg:
>
> Is is possible to split out the m68k stuff from the generic nommu stuff?

I could do that. Usually the actual mm changes have been
a pretty small set of this. Often only 1 or 2 patches.


> (or 
> maybe I am missing the point of this patch? - it is for review/inclusion into 
> the -mm tree, or just for end users wanting to use 2.6.21?)

This is specifically for review and inclusion in main line.


> The patch is labeled uClinux (MMU-less), which I read as generic, but the 
> majority has to do with only m68knommu.

Well, if any non-mmu architecture people sent me patches that
made sense for me to push upstream I would include them here.
But that doesn't happen very often. They generally do it
themselves.

Historically the first -uc patches had m68knommu, h8300 and v850
as well as the non-mmu changes in it.


>  arch/m68knommu/Kconfig                   |   12
>  arch/m68knommu/Makefile                  |    4
>  arch/m68knommu/kernel/process.c          |    2
>  arch/m68knommu/kernel/setup.c            |  116 +---
>  arch/m68knommu/kernel/time.c             |    9
>  arch/m68knommu/mm/memory.c               |  100 ---
>  arch/m68knommu/platform/5206/config.c    |    8
>  arch/m68knommu/platform/5206e/config.c   |    7
>  arch/m68knommu/platform/520x/config.c    |  122 ++++
>  arch/m68knommu/platform/523x/config.c    |    8
>  arch/m68knommu/platform/5249/config.c    |   51 +
>  arch/m68knommu/platform/5272/config.c    |    7
>  arch/m68knommu/platform/527x/config.c    |    7
>  arch/m68knommu/platform/528x/config.c    |    7
>  arch/m68knommu/platform/5307/config.c    |    5
>  arch/m68knommu/platform/5307/entry.S     |   20
>  arch/m68knommu/platform/5307/ints.c      |   23
>  arch/m68knommu/platform/5307/timers.c    |   10
>  arch/m68knommu/platform/532x/config.c    |   46 +
>  arch/m68knommu/platform/5407/config.c    |    7
>  arch/m68knommu/platform/68328/config.c   |    3
>  arch/m68knommu/platform/68360/config.c   |    2
>  arch/m68knommu/platform/68EZ328/config.c |    2
>  arch/m68knommu/platform/68VZ328/config.c |    7
>  include/asm-m68knommu/dma.h              |    2
>  include/asm-m68knommu/hw_irq.h           |    4
>  include/asm-m68knommu/m528xsim.h         |    3
>  include/asm-m68knommu/m532xsim.h         |   85 ++-
>  include/asm-m68knommu/machdep.h          |   50 -
>  include/asm-m68knommu/mcfuart.h          |   11
>  include/asm-m68knommu/pgtable.h          |    7
>  include/asm-m68knommu/timex.h            |   24
>  include/asm-m68knommu/uaccess.h          |   11
>  drivers/net/fec.c                        |   71 +-
>  drivers/serial/68328serial.c             |   59 --
>  drivers/serial/mcf.c                     |  826 +++++++++++++++++++++++++++++
>
> The only generic stuff is:
>
>  Makefile                                 |    2
>  drivers/pci/pci.c                        |    2
>  fs/binfmt_flat.c                         |    2
>  fs/namei.c                               |    2
>  mm/nommu.c                               |   15
>  mm/page_alloc.c                          |    8
>
> I looked at those, and had a question:
>
> (copy and paste screws up the formatting, sorry):
>
> > diff -Naur linux-2.6.21/fs/namei.c linux-2.6.21-uc0/fs/namei.c
> > --- linux-2.6.21/fs/namei.c     2007-05-01 17:12:53.000000000 +1000
> > +++ linux-2.6.21-uc0/fs/namei.c 2007-05-01 17:16:18.000000000 +1000
> > @@ -120,12 +120,14 @@
> >         int retval;
> >         unsigned long len = PATH_MAX;
> >
> > +#ifdef CONFIG_MMU
> >         if (!segment_eq(get_fs(), KERNEL_DS)) {
> >                 if ((unsigned long) filename >= TASK_SIZE)
> >                         return -EFAULT;
> >                 if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
> >                         len = TASK_SIZE - (unsigned long) filename;
> >         }
> > +#endif
> >
> >         retval = strncpy_from_user(page, filename, len);
> >         if (retval > 0) {
>
> 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.

Regards
Greg


------------------------------------------------------------------------
Greg Ungerer  --  Chief Software Dude       EMAIL:     gerg@snapgear.com
SnapGear -- a Secure Computing Company      PHONE:       +61 7 3435 2888
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