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SubjectRe: [PATCH 2/4] x86: ioremap: fix physical address check
On Mon, 14 Jun 2010 09:18:23 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> On Fri, 11 Jun 2010 10:43:27 -0700
> "H. Peter Anvin" <hpa@zytor.com> wrote:
>
> > On 06/11/2010 02:20 AM, Kenji Kaneshige wrote:
> > > If the physical address is too high to be handled by ioremap() in
> > > x86_32 PAE (e.g. more than 36-bit physical address), ioremap() must
> > > return error (NULL). However, current x86 ioremap try to map this too
> > > high physical address, and it causes unexpected behavior.
> >
> > What unexpected behavior? It is perfectly legitimately to map such a
> > high address in PAE mode. We have a 36-bit kernel-imposed limit on
> > *RAM* in 32-bit mode (because we can't manage more than that), but there
> > is no reason it should apply to I/O.
> >
>
> I'm sorry for lack of study.

Now, __ioremap_caller() gets 64 bit argument as physical address.
== 2.6.35-rc2 ==
static void __iomem *__ioremap_caller(resource_size_t phys_addr,
unsigned long size, unsigned long prot_val, void *caller)
{
==
And check physical address is valid based on the value got from cpuid.
==
if (!phys_addr_valid(phys_addr)) {
printk(KERN_WARNING "ioremap: invalid physical address %llx\n",
(unsigned long long)phys_addr);
WARN_ON_ONCE(1);
return NULL;
}
==

At 1st, this seems buggy.
==
/*
* Don't allow anybody to remap normal RAM that we're using..
*/
for (pfn = phys_addr >> PAGE_SHIFT;
(pfn << PAGE_SHIFT) < (last_addr & PAGE_MASK);
pfn++) {
int is_ram = page_is_ram(pfn);

if (is_ram && pfn_valid(pfn) && !PageReserved(pfn_to_page(pfn)))
return NULL;
WARN_ON_ONCE(is_ram);
}
==
If phys_addr > 44bit, pfn should be 64bit. don't it ?
Then, page_is_ram should eat 64bit arguments.
But here, assume phys_addr < 44bit and continue.

Next,
===
offset = phys_addr & ~PAGE_MASK;
phys_addr &= PAGE_MASK;
size = PAGE_ALIGN(last_addr+1) - phys_addr;

this mask ops is bad. as the patch-1 shows.

And, finally, calls get_vm_area.

==
/*
* Ok, go for it..
*/
area = get_vm_area_caller(size, VM_IOREMAP, caller);
if (!area)
goto err_free_memtype;
area->phys_addr = phys_addr;
vaddr = (unsigned long) area->addr;
==
Because area->phys_addr is 32bit. This may break something if we unmap this later.
And, page table operation is this.
==
if (ioremap_page_range(vaddr, vaddr + size, phys_addr, prot))
goto err_free_area;
==
Let's see lib/ioremap.c
==
int ioremap_page_range(unsigned long addr,
unsigned long end, unsigned long phys_addr, pgprot_t prot)
{
pgd_t *pgd;
==

Oh, phys_addr is unsigned long again....Then, Kenji-san, what's buggy is this check.
I think.
Thanks,
-Kame







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