MIPS: c-r4k: Sync icache when it fills from dcache

It is still necessary to handle icache coherency in flush_cache_range()
and copy_to_user_page() when the icache fills from the dcache, even
though the dcache does not need to be written back. However when this
handling was added in commit 2eaa7ec2 ("[MIPS] Handle I-cache
coherency in flush_cache_range()"), it did not do any icache flushing
when it fills from dcache.

Therefore fix r4k_flush_cache_range() to run
local_r4k_flush_cache_range() without taking into account whether icache
fills from dcache, so that the icache coherency gets handled. Checks are
also added in local_r4k_flush_cache_range() so that the dcache blast
doesn't take place when icache fills from dcache.

A test to mmap a page PROT_READ|PROT_WRITE, modify code in it, and
mprotect it to VM_READ|VM_EXEC (similar to case described in above
commit) can hit this case quite easily to verify the fix.

A similar check was added in commit f8829cae ("[MIPS] Fix aliasing
bug in copy_to_user_page / copy_from_user_page"), so also fix
copy_to_user_page() similarly, to call flush_cache_page() without taking
into account whether icache fills from dcache, since flush_cache_page()
already takes that into account to avoid performing a dcache flush.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Leonid Yegoshin <leonid.yegoshin@imgtec.com>
Cc: Manuel Lauss <manuel.lauss@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/12179/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/mm/c-r4k.c

@@ -492,7 +492,14 @@ static inline void local_r4k_flush_cache_range(void * args)
 	if (!(has_valid_asid(vma->vm_mm)))
 		return;
 
+	/*
+	 * If dcache can alias, we must blast it since mapping is changing.
+	 * If executable, we must ensure any dirty lines are written back far
+	 * enough to be visible to icache.
+	 */
+	if (cpu_has_dc_aliases || (exec && !cpu_has_ic_fills_f_dc))
 		r4k_blast_dcache();
+	/* If executable, blast stale lines from icache */
 	if (exec)
 		r4k_blast_icache();
 }
@@ -502,7 +509,7 @@ static void r4k_flush_cache_range(struct vm_area_struct *vma,
 {
 	int exec = vma->vm_flags & VM_EXEC;
 
-	if (cpu_has_dc_aliases || (exec && !cpu_has_ic_fills_f_dc))
+	if (cpu_has_dc_aliases || exec)
 		r4k_on_each_cpu(local_r4k_flush_cache_range, vma);
 }
 

arch/mips/mm/init.c

@@ -196,7 +196,7 @@ void copy_to_user_page(struct vm_area_struct *vma,
 		if (cpu_has_dc_aliases)
 			SetPageDcacheDirty(page);
 	}
-	if ((vma->vm_flags & VM_EXEC) && !cpu_has_ic_fills_f_dc)
+	if (vma->vm_flags & VM_EXEC)
 		flush_cache_page(vma, vaddr, page_to_pfn(page));
 }