PATCH: Fix offset of mmap

PATCH: Fix offset of mmap

[H . J . Lu]

We should check if offset of mmap is on the page boundary.


H.J.
---
--- /tmp/tmp.20947.0	Fri Sep 14 10:05:33 2001
+++ arch/mips/kernel/syscall.c	Fri Sep 14 10:05:08 2001
@@ -82,6 +82,8 @@ out:
 asmlinkage unsigned long old_mmap(unsigned long addr, size_t len, int prot,
                                   int flags, int fd, off_t offset)
 {
+	if (offset & ~PAGE_MASK)
+		return -EINVAL;
 	return do_mmap2(addr, len, prot, flags, fd, offset >> PAGE_SHIFT);
 }
 

Re: PATCH: Fix offset of mmap

[James Simmons]

> We should check if offset of mmap is on the page boundary.

I believe this would break certain pieces of hardware. For example the
mq200 framebuffer in the sigmarion is not paged aligned. You have to
supply a offset to make it work.

Re: PATCH: Fix offset of mmap

[H . J . Lu]

On Fri, Sep 14, 2001 at 10:10:58AM -0700, James Simmons wrote:
> 
> > We should check if offset of mmap is on the page boundary.
> 
> I believe this would break certain pieces of hardware. For example the
> mq200 framebuffer in the sigmarion is not paged aligned. You have to
> supply a offset to make it work.

How do you mmap a memory whose offset is not page aligned? The code
here is

return do_mmap2(addr, len, prot, flags, fd, offset >> PAGE_SHIFT);
					    ^^^^^^^^^^^^^^^^^^^^

It is up to the user code to make sure everything is ok.


H.J.

Re: PATCH: Fix offset of mmap

[James Simmons]

> > I believe this would break certain pieces of hardware. For example the
> > mq200 framebuffer in the sigmarion is not paged aligned. You have to
> > supply a offset to make it work.
> 
> How do you mmap a memory whose offset is not page aligned? The code
> here is
> 
> return do_mmap2(addr, len, prot, flags, fd, offset >> PAGE_SHIFT);
> 					    ^^^^^^^^^^^^^^^^^^^^
> 
> It is up to the user code to make sure everything is ok.

Sorry. Mix up in the meaning of offset.