* Re: [PATCH] ioremap: fix iounmap numpages
2007-07-02 0:33 ` Dave Young
@ 2007-07-02 4:01 ` Dmitry Monakhov
2007-07-02 19:08 ` Jeremy Fitzhardinge
1 sibling, 0 replies; 5+ messages in thread
From: Dmitry Monakhov @ 2007-07-02 4:01 UTC (permalink / raw)
To: Dave Young; +Cc: Jeremy Fitzhardinge, Chuck Ebbert, linux-kernel
On 00:33 Пнд 02 Июл , Dave Young wrote:
> > On 6/29/07, Jeremy Fitzhardinge <jeremy@goop.org> wrote:
> > Dave Young wrote:
> > > Hi,
> > > The second parameter of change_page_attr in iounmap is wrong, it should
> > be (p->size - 1) >> PAGE_SHIFT
> > >
> >
> > Why's that? Isn't p->size always going to be a pagesize multiple; in
> > which case, why would you want to change_page_attr on n-1 pages?
> >
> > Are you seeing a problem that this patch fixes?
> >
> > J
> >
> Hi,
> Please read the ioremap_nocache function, the page number is calculated by:
>
> last_addr = phys_addr + size - 1;
> npages = (last_addr - phys_addr) >> PAGE_SHIFT;
>
> but the pages number in iounmap is p->size >> PAGE_SHIFT, the result
> is not consistent.
It's absolutely true in fact last page is just guard page witch can't be
toched. And (size -1) magic was used in all io**map code before,
but when someone remove this magic by occasion :)
BTW: XEN currently use this magic.
arch/i386/mm/ioremap-xen.c: iounmap() {
....
/* p->size includes the guard page, but cpa doesn't like that */
change_page_attr(virt_to_page(bus_to_virt(p->phys_addr)),
(p->size - PAGE_SIZE) >> PAGE_SHIFT
>
> If there's no netsc520 device then the netsc520 mtd driver
> initializing will cause oops.
> I debugged it with some printk messages, find that the ioremap_nocache
> call change_page_attr 256 times, but the iounmap call change_page_attr
> more than 256 times, so kernel oops. please finid the oops message:
>
> ------------[ cut here ]------------
> kernel BUG at arch/i386/mm/pageattr.c:175!
> invalid opcode: 0000 [#1]
> PREEMPT SMP
> Modules linked in: cfi_probe gen_probe netsc520 mtdpart mtdcore
> chipreg map_funcs snd_seq_dummy snd_seq_oss snd_seq_midi_event
> snd_seq snd_seq_device snd_pcm_oss snd_mixer_oss snd_hda_intel snd_pcm
> snd_timer snd soundcore snd_page_alloc capability common
> cap e100 mii agpgart pcspkr psmouse
> CPU: 0
> EIP: 0060:[<c0118ff5>] Not tainted VLI
> EFLAGS: 00010082 (2.6.22-rc6 #15)
> EIP is at __change_page_attr+0x185/0x1a0
> eax: 0000afe0 ebx: c1006000 ecx: c100afe0 edx: c1000000
> esi: c057fc00 edi: c0300000 ebp: 00000163 esp: f74c7f40
> ds: 007b es: 007b fs: 00d8 gs: 0033 ss: 0068
> Process modprobe (pid: 1440, ti=f74c6000 task=f742aa20 task.ti=f74c6000)
> Stack: 00000163 c1006000 00000100 00000000 00000101 c011904b 00000202
> 00000163
> f7b46ee0 f8980000 c1004000 f74c6000 c0118c60 f886e237 f88810a6
> f8881600
> 0805f9c8 00000001 f88830d2 f88810cc 00100000 00000000 00200000
> 00000000
> Call Trace:
> [<c011904b>] change_page_attr+0x3b/0x70
> [<c0118c60>] iounmap+0xd0/0xe0
> [<f88830d2>] init_netsc520+0xd2/0xf5 [netsc520]
> [<c01451a9>] sys_init_module+0xd9/0x140
> [<c0104238>] syscall_call+0x7/0xb
> [<c0420000>] packet_rcv+0x90/0x320
> =======================
> Code: c3 85 db b8 f4 ff ff ff 74 af a1 80 15 5a c0 89 d9 89 fa 29 c1
> c1 f9 05 89 f0 c1 e1 0c 09 e9 e8 22 fe ff ff 89 d9 e9 07 f
> f ff ff <0f> 0b eb fe 0f 0b eb fe 0f 0b eb fe eb 0d 90 90 90 90 90 90 90
> EIP: [<c0118ff5>] __change_page_attr+0x185/0x1a0 SS:ESP 0068:f74c7f40
>
> Regards
> dave
> -
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^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] ioremap: fix iounmap numpages
2007-07-02 0:33 ` Dave Young
2007-07-02 4:01 ` Dmitry Monakhov
@ 2007-07-02 19:08 ` Jeremy Fitzhardinge
1 sibling, 0 replies; 5+ messages in thread
From: Jeremy Fitzhardinge @ 2007-07-02 19:08 UTC (permalink / raw)
To: Dave Young; +Cc: Linus Torvalds, Chuck Ebbert, linux-kernel, Andi Kleen
Dave Young wrote:
>> On 6/29/07, Jeremy Fitzhardinge <jeremy@goop.org> wrote:
>> Dave Young wrote:
>> > Hi,
>> > The second parameter of change_page_attr in iounmap is wrong, it
>> should be (p->size - 1) >> PAGE_SHIFT
>> >
>>
>> Why's that? Isn't p->size always going to be a pagesize multiple; in
>> which case, why would you want to change_page_attr on n-1 pages?
>>
>> Are you seeing a problem that this patch fixes?
>>
>> J
>>
> Hi,
> Please read the ioremap_nocache function, the page number is
> calculated by:
>
> last_addr = phys_addr + size - 1;
> npages = (last_addr - phys_addr) >> PAGE_SHIFT;
>
> but the pages number in iounmap is p->size >> PAGE_SHIFT, the result
> is not consistent.
>
> If there's no netsc520 device then the netsc520 mtd driver
> initializing will cause oops.
> I debugged it with some printk messages, find that the ioremap_nocache
> call change_page_attr 256 times, but the iounmap call change_page_attr
> more than 256 times, so kernel oops. please finid the oops message:
OK, so the problem is that get_vm_area allocates the vm_area with an
extra page added as a guard page. iounmap uses p->size directly,
without taking the guard page into account.
I don't see why this doesn't cause more problems. I guess uncached
iomappings are not used that much?
Anyway, I think this is the right fix:
Subject: fix iounmap's use of vm_struct's size field
get_vm_area always returns an area with an adjacent guard page. That
guard page is included in vm_struct.size. iounmap uses vm_struct.size
to determine how much address space needs to have change_page_attr
applied to it, which will BUG if applied to the guard page.
This patch adds a helper function - get_vm_area_size() in
linux/vmalloc.h - to return the actual size of a vm area, and uses it
to make iounmap do the right thing. There are probably other places
which should be using get_vm_area_size().
Thanks to Dave Young <hidave.darkstar@gmail.com> for debugging the
problem.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Dave Young <hidave.darkstar@gmail.com>
Cc: Chuck Ebbert <cebbert@redhat.com>
Cc: Andi Kleen <ak@suse.de>
---
arch/i386/mm/ioremap.c | 2 +-
include/linux/vmalloc.h | 6 ++++++
2 files changed, 7 insertions(+), 1 deletion(-)
===================================================================
--- a/arch/i386/mm/ioremap.c
+++ b/arch/i386/mm/ioremap.c
@@ -193,7 +193,7 @@ void iounmap(volatile void __iomem *addr
/* Reset the direct mapping. Can block */
if ((p->flags >> 20) && p->phys_addr < virt_to_phys(high_memory) - 1) {
change_page_attr(virt_to_page(__va(p->phys_addr)),
- p->size >> PAGE_SHIFT,
+ get_vm_area_size(p) >> PAGE_SHIFT,
PAGE_KERNEL);
global_flush_tlb();
}
===================================================================
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -70,6 +70,12 @@ extern int map_vm_area(struct vm_struct
struct page ***pages);
extern void unmap_kernel_range(unsigned long addr, unsigned long size);
+static inline size_t get_vm_area_size(const struct vm_struct *area)
+{
+ /* return actual size without guard page */
+ return area->size - PAGE_SIZE;
+}
+
/* Allocate/destroy a 'vmalloc' VM area. */
extern struct vm_struct *alloc_vm_area(size_t size);
extern void free_vm_area(struct vm_struct *area);
^ permalink raw reply [flat|nested] 5+ messages in thread