Re: [PATCH 2/2] MIPS: Flush highmem pages from dcache in __flush_icache_page

From: Lars Persson
Date: Wed Feb 24 2016 - 03:02:54 EST

On 02/22/2016 07:09 PM, Paul Burton wrote:
When a page is to be mapped executable for userspace, we can presume
that the icache doesn't contain anything valid for its address range but
we cannot be sure that its content has been written back from the dcache
to L2 or memory further out. If the icache fills from those memories,
ie. does not fill from the dcache, then we need to ensure that content
has been flushed from the dcache. This was being done for lowmem pages
but not for highmem pages. Fix this by mapping the page & flushing its
content from the dcache in __flush_icache_page, before the page is
provided to userland.

Reviewed-by: Lars Persson <larper@xxxxxxxx>

Signed-off-by: Paul Burton <paul.burton@xxxxxxxxxx>


arch/mips/mm/cache.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
index 3f159ca..734cb2f 100644
--- a/arch/mips/mm/cache.c
+++ b/arch/mips/mm/cache.c
@@ -16,6 +16,7 @@
#include <linux/mm.h>

#include <asm/cacheflush.h>
+#include <asm/highmem.h>
#include <asm/processor.h>
#include <asm/cpu.h>
#include <asm/cpu-features.h>
@@ -124,10 +125,14 @@ void __flush_icache_page(struct vm_area_struct *vma, struct page *page)
unsigned long addr;

if (PageHighMem(page))
- return;
+ addr = (unsigned long)kmap_atomic(page);
+ else
+ addr = (unsigned long)page_address(page);

- addr = (unsigned long) page_address(page);
+ if (PageHighMem(page))
+ __kunmap_atomic((void *)addr);