Fatal exception while changing the memory entries in ARMv7 MMU

[Utkarsh Rai]

Your advice worked, but not in the way it was supposed to (or maybe I
didn't do it right). I got a fatal exception even when I used the aligned
attribute. However, when I allocate memory using posix_memalign() I get the
desired result.

On Sat, Jul 25, 2020 at 9:45 PM Gedare Bloom <gedare at rtems.org> wrote:

> On Sat, Jul 25, 2020 at 9:44 AM Utkarsh Rai <utkarsh.rai60 at gmail.com>
> wrote:
> >
> > Hello,
> > While changing the memory entries for a section in the ARMv7 MMU using
> 'arm_cp15_set_translation_table_entries()' I get fatal exception error. On
> stepping through the debugger, the exception occurs when invalidating the
> data TLB entries, using 'arm_cp15_tlb_data_invalidate_entry()'.
> >
> > You can view the relevant snippet here. Interestingly enough, the fatal
> exception occurs when I change the memory attribute from READ/WRITE to READ
> ONLY. Can someone point out my mistake?
>
> My best guess: The block of memory you pass is in global space. It is
> not likely to be page aligned. So when you change to read-only, you
> probably change some other global variables to read-only also, and
> then something tries to write to them.
>
> To see if that is the problem, use the aligned() attribute (we have
> RTEMS_ALIGNED) with the page size.
>
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>
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