From: Scott Wood Date: Tue, 5 Feb 2008 19:43:26 +0000 (+1100) Subject: [POWERPC] update_mmu_cache: Don't cache-flush non-readable pages X-Git-Tag: firefly_0821_release~22796^2~29 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=551ed332da2f52daf5d01fc76d2a894aba79d316;p=firefly-linux-kernel-4.4.55.git [POWERPC] update_mmu_cache: Don't cache-flush non-readable pages Currently, update_mmu_cache will crash if given a no-access PTE. There's no need to synchronize dcache/icache unless it's an exec mapping -- however, due to the existence of older glibc versions that execute out of a read-but-no-exec page, readability is tested instead. This assumes no exec-only mappings; if such mappings become supported, they will need to go through the kmap_atomic() version of dcache/icache synchronization. This fixes a bug reported by some users where the kernel would crash while dumping core on a threaded program. Signed-off-by: Scott Wood Acked-by: Benjamin Herrenschmidt Signed-off-by: Paul Mackerras --- diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c index e8122447f019..c7d7bd43a251 100644 --- a/arch/powerpc/mm/mem.c +++ b/arch/powerpc/mm/mem.c @@ -483,7 +483,12 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address, */ _tlbie(address, 0 /* 8xx doesn't care about PID */); #endif - if (!PageReserved(page) + /* The _PAGE_USER test should really be _PAGE_EXEC, but + * older glibc versions execute some code from no-exec + * pages, which for now we are supporting. If exec-only + * pages are ever implemented, this will have to change. + */ + if (!PageReserved(page) && (pte_val(pte) & _PAGE_USER) && !test_bit(PG_arch_1, &page->flags)) { if (vma->vm_mm == current->active_mm) { __flush_dcache_icache((void *) address);