From: Russell King <rmk+kernel@arm.linux.org.uk>
Date: Tue, 29 Jul 2014 11:18:34 +0000 (+0100)
Subject: ARM: idmap: add identity mapping usage note
X-Git-Tag: firefly_0821_release~176^2~3485^2~4
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=c5cc87fa8ddf971682fc5dd112e2dfacb11f30cd;p=firefly-linux-kernel-4.4.55.git

ARM: idmap: add identity mapping usage note

Add a note about the usage of the identity mapping; we do not support
accesses outside of the identity map region and kernel image while a
CPU is using the identity map.  This is because the identity mapping
may overwrite vmalloc space, IO mappings, the vectors pages, etc.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---

diff --git a/arch/arm/mm/idmap.c b/arch/arm/mm/idmap.c
index d7a0ee898d24..c447ec70e868 100644
--- a/arch/arm/mm/idmap.c
+++ b/arch/arm/mm/idmap.c
@@ -9,6 +9,11 @@
 #include <asm/sections.h>
 #include <asm/system_info.h>
 
+/*
+ * Note: accesses outside of the kernel image and the identity map area
+ * are not supported on any CPU using the idmap tables as its current
+ * page tables.
+ */
 pgd_t *idmap_pgd;
 phys_addr_t (*arch_virt_to_idmap) (unsigned long x);