linux-kernel - [PATCH v5 07/10] arm64/mm: Don't flush the data cache if the page is unmapped by XPFO

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Message-Id: <20170809200755.11234-8-tycho@docker.com>
Date:   Wed,  9 Aug 2017 14:07:52 -0600
From:   Tycho Andersen <tycho@...ker.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, kernel-hardening@...ts.openwall.com,
        Marco Benatto <marco.antonio.780@...il.com>,
        Juerg Haefliger <juerg.haefliger@...onical.com>,
        Juerg Haefliger <juerg.haefliger@....com>
Subject: [PATCH v5 07/10] arm64/mm: Don't flush the data cache if the page is unmapped by XPFO

From: Juerg Haefliger <juerg.haefliger@....com>

If the page is unmapped by XPFO, a data cache flush results in a fatal
page fault. So don't flush in that case.

Signed-off-by: Juerg Haefliger <juerg.haefliger@...onical.com>
Tested-by: Tycho Andersen <tycho@...ker.com>
---
 arch/arm64/mm/flush.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c
index 21a8d828cbf4..e17a063b2df2 100644
--- a/arch/arm64/mm/flush.c
+++ b/arch/arm64/mm/flush.c
@@ -20,6 +20,7 @@
 #include <linux/export.h>
 #include <linux/mm.h>
 #include <linux/pagemap.h>
+#include <linux/xpfo.h>
 
 #include <asm/cacheflush.h>
 #include <asm/cache.h>
@@ -30,7 +31,9 @@ void sync_icache_aliases(void *kaddr, unsigned long len)
 	unsigned long addr = (unsigned long)kaddr;
 
 	if (icache_is_aliasing()) {
-		__clean_dcache_area_pou(kaddr, len);
+		/* Don't flush if the page is unmapped by XPFO */
+		if (!xpfo_page_is_unmapped(virt_to_page(kaddr)))
+			__clean_dcache_area_pou(kaddr, len);
 		__flush_icache_all();
 	} else {
 		flush_icache_range(addr, addr + len);
-- 
2.11.0