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ARC: Brown paper bag bug in macro for checking cache color

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The VM_EXEC check in update_mmu_cache() was getting optimized away
because of a stupid error in definition of macro addr_not_cache_congruent()

The intention was to have the equivalent of following:

	if (a || (1 ? b : 0))

but we ended up with following:

	if (a || 1 ? b : 0)

And because precedence of '||' is more that that of '?', gcc was optimizing
away evaluation of <a>

Nasty Repercussions:
1. For non-aliasing configs it would mean some extraneous dcache flushes
   for non-code pages if U/K mappings were not congruent.
2. For aliasing config, some needed dcache flush for code pages might
   be missed if U/K mappings were congruent.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
This commit is contained in:
Vineet Gupta 2013-05-22 18:38:10 +05:30
parent a950549c67
commit 3e87974dec
2 changed files with 5 additions and 2 deletions
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4
arch/arc/include/asm/cacheflush.h
View File

@ -99,8 +99,10 @@ static inline int cache_is_vipt_aliasing(void)
* checks if two addresses (after page aligning) index into same cache set
*/
#define addr_not_cache_congruent(addr1, addr2) \
({ \
cache_is_vipt_aliasing() ? \
(CACHE_COLOR(addr1) != CACHE_COLOR(addr2)) : 0 \
(CACHE_COLOR(addr1) != CACHE_COLOR(addr2)) : 0; \
})
#define copy_to_user_page(vma, page, vaddr, dst, src, len) \
do { \

3
arch/arc/mm/tlb.c
View File

@ -444,7 +444,8 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long vaddr_unaligned,
* so userspace sees the right data.
* (Avoids the flush for Non-exec + congruent mapping case)
*/
if (vma->vm_flags & VM_EXEC || addr_not_cache_congruent(paddr, vaddr)) {
if ((vma->vm_flags & VM_EXEC) ||
addr_not_cache_congruent(paddr, vaddr)) {
struct page *page = pfn_to_page(pte_pfn(*ptep));
int dirty = test_and_clear_bit(PG_arch_1, &page->flags);