lkml.org 
[lkml]   [2010]   [Oct]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] ARM: allow, but warn, when issuing ioremap() on RAM
    On Fri, Oct 08, 2010 at 10:41:42PM -0400, Nicolas Pitre wrote:
    > On Sat, 9 Oct 2010, Russell King - ARM Linux wrote:
    >
    > > On Fri, Oct 08, 2010 at 05:00:46PM -0700, Greg KH wrote:
    > > > But you can't expect that you make this change, and not fix up the
    > > > drivers, and people would be happy, right? The rule for API changes
    > > > like this, or anything, is that the person making the change fixes the
    > > > other drivers, and that seems to be the issue here.
    > >
    > > Let's entirely revert the change and wait for people's data to be
    > > corrupted then. I don't have the time nor the motivation to work
    > > through crap driver code to fix up these unreliable games which are
    > > already illegal on platforms such as x86.
    > >
    > > If people want their system to be unpredictable, then let's carry on
    > > giving them the rope to hang themselves in that manner.
    > >
    > > > Any pointers to patches where people have fixed up the drivers?
    > >
    > > Despite the discussion, I'm unaware of anyone really taking the issue
    > > seriously and producing any patches during the last six months.
    > >
    > > So, I say sod it, let's revert the change.
    >
    > I think that the real issue here is to avoid breaking those drivers
    > which were using this legitimately. So what about this compromize
    > instead:
    >
    > diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c
    > index 99627d3..4f071e4 100644
    > --- a/arch/arm/mm/ioremap.c
    > +++ b/arch/arm/mm/ioremap.c
    > @@ -201,6 +201,15 @@ void __iomem * __arm_ioremap_pfn_caller(unsigned long pfn,
    > if (pfn >= 0x100000 && (__pfn_to_phys(pfn) & ~SUPERSECTION_MASK))
    > return NULL;
    >
    > + /*
    > + * Warn if RAM is mapped to discourage this usage. Let's forbid it
    > + * outright on ARMv6+ where this became architecturally undefined
    > + * in theory and causes memory corruption in practice.
    > + */
    > + if (WARN_ON(pfn_valid(pfn)))
    > + if (__LINUX_ARM_ARCH__ >= 6)
    > + return NULL;
    > +
    > type = get_mem_type(mtype);
    > if (!type)
    > return NULL;
    >

    That looks good to me, anyone else object to this?

    Now we also need a way to fix the drivers for real on ARMv6+ now...

    thanks,

    greg k-h


    \
     
     \ /
      Last update: 2010-10-09 05:15    [W:0.029 / U:4.104 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site