Re: [PATCH 1/2] x86: ioremap: fix wrong physical address handling

Kenji Kaneshige
2010-06-21T01:41:54Z

(2010/06/18 20:07), Jeremy Fitzhardinge wrote:
> On 06/18/2010 04:22 AM, Kenji Kaneshige wrote:
>> Current x86 ioremap() doesn't handle physical address higher than
>> 32-bit properly in X86_32 PAE mode. When physical address higher than
>> 32-bit is passed to ioremap(), higher 32-bits in physical address is
>> cleared wrongly. Due to this bug, ioremap() can map wrong address to
>> linear address space.
>>
>> In my case, 64-bit MMIO region was assigned to a PCI device (ioat
>> device) on my system. Because of the ioremap()'s bug, wrong physical
>> address (instead of MMIO region) was mapped to linear address space.
>> Because of this, loading ioatdma driver caused unexpected behavior
>> (kernel panic, kernel hangup, ...).
>>
>> Signed-off-by: Kenji Kaneshige<kaneshige.kenji@jp.fujitsu.com>
>>
>> ---
>> arch/x86/mm/ioremap.c | 12 +++++-------
>> include/linux/io.h | 4 ++--
>> include/linux/vmalloc.h | 2 +-
>> lib/ioremap.c | 10 +++++-----
>> mm/vmalloc.c | 2 +-
>> 5 files changed, 14 insertions(+), 16 deletions(-)
>>
>> Index: linux-2.6.34/arch/x86/mm/ioremap.c
>> ===================================================================
>> --- linux-2.6.34.orig/arch/x86/mm/ioremap.c
>> +++ linux-2.6.34/arch/x86/mm/ioremap.c
>> @@ -62,8 +62,8 @@ int ioremap_change_attr(unsigned long va
>> static void __iomem *__ioremap_caller(resource_size_t phys_addr,
>> unsigned long size, unsigned long prot_val, void *caller)
>> {
>> - unsigned long pfn, offset, vaddr;
>> - resource_size_t last_addr;
>> + unsigned long offset, vaddr;
>> + resource_size_t pfn, last_pfn, last_addr;
>>
>
> Why is pfn resource_size_t here? Is it to avoid casting, or does it
> actually need to hold more than 32 bits? I don't see any use of pfn
> aside from the page_is_ram loop, and I don't think that can go beyond 32
> bits. If you're worried about boundary conditions at the 2^44 limit,
> then you can make last_pfn inclusive, or compute num_pages and use that
> for the loop condition.
>

The reason I changed here was phys_addr might be higher than 2^44. After
the discussion, I realized there would probably be many other codes that
cannot handle more than 32-bits pfn, and this would cause problems even
if I changed ioremap() to be able to handle more than 32-bits pfn. So I
decided to focus on making 44-bits physical address work properly this
time. But, I didn't find any reason to make it go back to unsigned long.
So I still make it resource_size_t even in v.3. Is there any problem on
this change? And I don't understand why pfn can't go beyond 32-bits.
Could you tell me why?

>> const resource_size_t unaligned_phys_addr = phys_addr;
>> const unsigned long unaligned_size = size;
>> struct vm_struct *area;
>> @@ -100,10 +100,8 @@ static void __iomem *__ioremap_caller(re
>> /*
>> * 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++) {
>> -
>> + last_pfn = last_addr>> PAGE_SHIFT;
>>
>
> If last_addr can be non-page aligned, should it be rounding up to the
> next pfn rather than rounding down? Ah, looks like you fix it in the
> second patch.
>

Yes, I fixed it in the [PATCH 2/2].

Thanks,
Kenji Kaneshige