Re: CVS commit: src/sys/arch/mips/include

[Matt Thomas <matt%3am-software.com@localhost>]

On Jul 23, 2014, at 1:46 PM, Joerg Sonnenberger 
<joerg%britannica.bec.de@localhost> wrote:

> On Tue, Jul 22, 2014 at 10:40:02PM +0100, Alexander Nasonov wrote:
>> Matt Thomas wrote:
>>> 
>>> On Jul 22, 2014, at 2:27 PM, Alexander Nasonov <alnsn%yandex.ru@localhost> 
>>> wrote:
>>>> I allocate with the X flag and it seems to work:
>>>> 
>>>> /* in sljitExecAllocator.c */
>>>>       return (void *)uvm_km_alloc(module_map, size,
>>>>           PAGE_SIZE, UVM_KMF_WIRED | UVM_KMF_ZERO | UVM_KMF_EXEC);
>>> 
>>> ok.  Then you need don't a hook for cache flushing
>>> 
>>> pmap_protect(vm_map_pamp(module_map), va, size) will do that for you.
>>> At least for arm/mips/ppc/vax.  (e.g. changing a writeable exec page
>>> to read-only automatically causes it exec cleaned).
>> 
>> sljit allocates 64K exec chucks which are managed by a special allocator.
>> You need to run pmap_protect for each chunk. I think it's cheaper to
>> flush icache.
> 
> Wouldn't it be preferable to have *two* mappings for the code? One which
> is writeable and another which is executable?

won’t give you cleaning by the pmap since that’s done by pmap_protect.