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Commit a188ad2b authored by George G. Davis's avatar George G. Davis Committed by Russell King
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[ARM] 3762/1: Fix ptrace cache coherency bug for ARM1136 VIPT nonaliasing Harvard caches 



Patch from George G. Davis

Resolve ARM1136 VIPT non-aliasing cache coherency issues observed when
using ptrace to set breakpoints and cleanup copy_{to,from}_user_page()
while we're here as requested by Russell King because "it's also far
too heavy on non-v6 CPUs".

NOTES:

1. Only access_process_vm() calls copy_{to,from}_user_page().
2. access_process_vm() calls get_user_pages() to pin down the "page".
3. get_user_pages() calls flush_dcache_page(page) which ensures cache
   coherency between kernel and userspace mappings of "page".  However
   flush_dcache_page(page) may not invalidate I-Cache over this range
   for all cases, specifically, I-Cache is not invalidated for the VIPT
   non-aliasing case.  So memory is consistent between kernel and user
   space mappings of "page" but I-Cache may still be hot over this
   range.  IOW, we don't have to worry about flush_cache_page() before
   memcpy().
4. Now, for the copy_to_user_page() case, after memcpy(), we must flush
   the caches so memory is consistent with kernel cache entries and
   invalidate the I-Cache if this mm region is executable.  We don't
   need to do anything after memcpy() for the copy_from_user_page()
   case since kernel cache entries will be invalidated via the same
   process above if we access "page" again.  The flush_ptrace_access()
   function (borrowed from SPARC64 implementation) is added to handle
   cache flushing after memcpy() for the copy_to_user_page() case.

Signed-off-by: default avatarGeorge G. Davis <gdavis@mvista.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 57bcdafc

arch/arm/mm/flush.c

+26 −0
Original line number Diff line number Diff line
@@ -87,6 +87,32 @@ void flush_cache_page(struct vm_area_struct *vma, unsigned long user_addr, unsig 
	if (cache_is_vipt_aliasing())

		flush_pfn_alias(pfn, user_addr);

}



void flush_ptrace_access(struct vm_area_struct *vma, struct page *page,

			 unsigned long uaddr, void *kaddr,

			 unsigned long len, int write)

{

	if (cache_is_vivt()) {

		if (cpu_isset(smp_processor_id(), vma->vm_mm->cpu_vm_mask)) {

			unsigned long addr = (unsigned long)kaddr;

			__cpuc_coherent_kern_range(addr, addr + len);

		}

		return;

	}



	if (cache_is_vipt_aliasing()) {

		flush_pfn_alias(page_to_pfn(page), uaddr);

		return;

	}



	/* VIPT non-aliasing cache */

	if (cpu_isset(smp_processor_id(), vma->vm_mm->cpu_vm_mask) &&

	    vma->vm_flags | VM_EXEC) {

		unsigned long addr = (unsigned long)kaddr;

		/* only flushing the kernel mapping on non-aliasing VIPT */

		__cpuc_coherent_kern_range(addr, addr + len);

	}

}

#else

#define flush_pfn_alias(pfn,vaddr)	do { } while (0)

#endif

include/asm-arm/cacheflush.h

+15 −3
Original line number Diff line number Diff line
@@ -247,14 +247,12 @@ extern void dmac_flush_range(unsigned long, unsigned long); 
 */

#define copy_to_user_page(vma, page, vaddr, dst, src, len) \

	do {							\

		flush_cache_page(vma, vaddr, page_to_pfn(page));\

		memcpy(dst, src, len);				\

		flush_dcache_page(page);			\

		flush_ptrace_access(vma, page, vaddr, dst, len, 1);\

	} while (0)



#define copy_from_user_page(vma, page, vaddr, dst, src, len) \

	do {							\

		flush_cache_page(vma, vaddr, page_to_pfn(page));\

		memcpy(dst, src, len);				\

	} while (0)
@@ -285,10 +283,24 @@ flush_cache_page(struct vm_area_struct *vma, unsigned long user_addr, unsigned l 
		__cpuc_flush_user_range(addr, addr + PAGE_SIZE, vma->vm_flags);

	}

}



static inline void

flush_ptrace_access(struct vm_area_struct *vma, struct page *page,

			 unsigned long uaddr, void *kaddr,

			 unsigned long len, int write)

{

	if (cpu_isset(smp_processor_id(), vma->vm_mm->cpu_vm_mask)) {

		unsigned long addr = (unsigned long)kaddr;

		__cpuc_coherent_kern_range(addr, addr + len);

	}

}

#else

extern void flush_cache_mm(struct mm_struct *mm);

extern void flush_cache_range(struct vm_area_struct *vma, unsigned long start, unsigned long end);

extern void flush_cache_page(struct vm_area_struct *vma, unsigned long user_addr, unsigned long pfn);

extern void flush_ptrace_access(struct vm_area_struct *vma, struct page *page,

				unsigned long uaddr, void *kaddr,

				unsigned long len, int write);

#endif



/*