On 06/21/2012 08:37 AM, Borislav Petkov wrote:
-unsigned long align_addr(unsigned long addr, struct file *filp,
- enum align_flags flags)
+unsigned long arch_align_addr(unsigned long addr, struct file *filp,
+ unsigned long pgoff, unsigned long flags,
+ enum mmap_allocation_direction direction)
Arguments vertical alignment too, not only addr alignment :-)
Will do.
{
- unsigned long tmp_addr;
+ unsigned long tmp_addr = PAGE_ALIGN(addr);
I'm guessing addr coming from arch_get_unmapped_area(_topdown) might not
be page-aligned in all cases?
That is my guess, too :)
In some places arch_get_unmapped_area(_topdown) called
PAGE_ALIGN(addr), so we should make sure it is called.
It is probably masking bugs in some old old application,
and calling it here really should not hurt.
- if (!(current->flags& PF_RANDOMIZE))
- return addr;
+ /* Always allow MAP_FIXED. Colouring is a performance thing only. */
+ if (flags& MAP_FIXED)
+ return tmp_addr;
Why here? Maybe we should push this MAP_FIXED check up in the
arch_get_unmapped_area(_topdown) and not call arch_align_addr() for
MAP_FIXED requests?
Or do you want to save some code duplication?
The problem is that certain other architectures have
data cache alignment requirements, where mis-aligning
somebody's mmap of a file could result in actual data
corruption.
This means that, for those architectures, we have to
refuse non-colour-aligned MAP_FIXED mappings.
On x86 we can allow them, so we do. But that decision
needs to be taken in architecture specific code, not
in the shared arch_get_unmapped_area(_topdown) :)
+ /*
+ * When aligning down, make sure we did not accidentally go up.
+ * The caller will check for underflow.
+ */
Can we add this comment to the x86-64 version of arch_align_addr too pls?
Will do.
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