Messages in this thread | | | Date | Thu, 10 Apr 2014 21:34:46 +0200 | From | Rabin Vincent <> | Subject | Re: [PATCH 2/2] arm: use fixmap for text patching when text is RO |
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On Mon, Apr 07, 2014 at 02:57:51PM +0100, Jon Medhurst (Tixy) wrote: > How does fixmap cope with cache colouring? Looking at the implementation > it looks like it doesn't and so fixmap use on ARM is possibly buggy. > > For the text patching case where we know there are no writeable mappings > [1] this should be OK if we used set_fixmap_nocache here, so long as we > also invalidated the dcache later for the proper virtual address.
OK. The dcache invalidation for the proper virtual address is btw already there via the call to flush_icache_range().
> [1] Can we know there are no writeable mappings though, the ftrace code > modifying patches from Kees Cook have there own way of modifying text > code permissions.
The ftrace patches does the modifications and the cache cleaning in stop_machine(), so there should not be any dirty cache lines from those writable mappings when we set up and write to these fixmaps. Do you still see a problem?
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