Messages in this thread | | | Date | Thu, 14 Feb 2008 18:14:02 +0100 | From | Andi Kleen <> | Subject | Re: [PATCH] Fix direct mapping correctly in ioremap |
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On Thu, Feb 14, 2008 at 05:03:23PM +0100, Ingo Molnar wrote: > > * Andi Kleen <andi@firstfloor.org> wrote: > > > - if (ioremap_change_attr(vaddr, size, mode) < 0) { > > + /* Fix up the direct mapping for the new cache attributes */ > > + err = ioremap_change_attr((unsigned long)__va(phys_addr), > > + size + offset, mode); > > Ugh. This would break the 32-bit kernel - if any phys_addr larger than > 1GB is passed in (which is the common case on 32-bit) then we'll start > changing the attributes of random (most likely user-space) pages! > That is because on 32-bit __va() does this: > > #define __va(x) ((void *)((unsigned long)(x)+PAGE_OFFSET)) > > where on 32-bit 3GB:1GB split PAGE_OFFSET is defined to 0xc0000000. > > So if a driver passes in the physical address of a PCI device with a BAR > at 0xe1000000 somewhere in the PCI aperture, we'll get > 0xe1000000+0xc0000000 == 0x91000000 - right in the middle of user-space. > > Changing attributes there is very wrong. (it could even crash the kernel > in certain circumstances.)
True. It needs a end_pfn_map check. I'll revise.
> Have you tried to boot this patch on 32-bit? There are a couple of new
Yes, it booted on several machines. Don't think I saw CPA messages, but i might have missed them.
> safety nets in the cpa code that would/should trigger very visibly - > such as the warning here: > > if (!pte_val(old_pte)) { > printk(KERN_WARNING "CPA: called for zero pte. " > "vaddr = %lx cpa->vaddr = %lx\n", address, > cpa->vaddr); > WARN_ON(1); > return -EINVAL; > } > > (these are already there in -git) > > Please have a look at how we solved the "secondary alias" 64-bit problem > in x86.git#mm and please resend against x86.git#mm if you still think > something is missing. Thanks,
I want this regression fixed in .25, so #mm is not an option for this.
-Andi
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