Re: [PATCH 2/4] x86: ioremap: fix physical address check

From: Kenji Kaneshige
Date: Mon Jun 14 2010 - 05:14:24 EST

Thank you Hiroyuki.

So many bugs in ioremap()...

Will try with those bugs fixed.

Kenji Kaneshige

(2010/06/14 17:59), KAMEZAWA Hiroyuki wrote:
On Mon, 14 Jun 2010 09:18:23 +0900
KAMEZAWA Hiroyuki<kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:

On Fri, 11 Jun 2010 10:43:27 -0700
"H. Peter Anvin"<hpa@xxxxxxxxx> 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);
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;
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.

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.


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