[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: George G. Davis <gdavis@mvista.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index b103e56..d438ce4 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c
@@ -87,6 +87,32 @@
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