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

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Message-ID: <4C15F2BD.9020904@jp.fujitsu.com>
Date:	Mon, 14 Jun 2010 18:13:33 +0900
From:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, jbarnes@...tuousgeek.org
Subject: Re: [PATCH 2/4] x86: ioremap: fix physical address check

Thank you Hiroyuki.

So many bugs in ioremap()...

Will try with those bugs fixed.

Thanks,
Kenji Kaneshige


(2010/06/14 17:59), KAMEZAWA Hiroyuki wrote:
> On Mon, 14 Jun 2010 09:18:23 +0900
> KAMEZAWA Hiroyuki<kamezawa.hiroyu@...fujitsu.com>  wrote:
>
>> On Fri, 11 Jun 2010 10:43:27 -0700
>> "H. Peter Anvin"<hpa@...or.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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