linux-kernel - [PATCH 3.12 120/127] mm: export symbol dependencies of is_zero

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Date:   Fri, 25 Nov 2016 09:30:33 +0100
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 120/127] mm: export symbol dependencies of is_zero_pfn()

From: Ard Biesheuvel <ard.biesheuvel@...aro.org>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 0b70068e47e8f0c813a902dc3d6def601fd15acb upstream.

In order to make the static inline function is_zero_pfn() callable by
modules, export its symbol dependencies 'zero_pfn' and (for s390 and
mips) 'zero_page_mask'.

We need this for KVM, as CONFIG_KVM is a tristate for all supported
architectures except ARM and arm64, and testing a pfn whether it refers
to the zero page is required to correctly distinguish the zero page
from other special RAM ranges that may also have the PG_reserved bit
set, but need to be treated as MMIO memory.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Acked-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 arch/mips/mm/init.c | 1 +
 arch/s390/mm/init.c | 1 +
 mm/memory.c         | 2 ++
 3 files changed, 4 insertions(+)

diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
index e205ef598e97..c247cf5a31cb 100644
--- a/arch/mips/mm/init.c
+++ b/arch/mips/mm/init.c
@@ -74,6 +74,7 @@
  */
 unsigned long empty_zero_page, zero_page_mask;
 EXPORT_SYMBOL_GPL(empty_zero_page);
+EXPORT_SYMBOL(zero_page_mask);
 
 /*
  * Not static inline because used by IP27 special magic initialization code
diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index ad446b0c55b6..1b30d5488f82 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -43,6 +43,7 @@ pgd_t swapper_pg_dir[PTRS_PER_PGD] __attribute__((__aligned__(PAGE_SIZE)));
 
 unsigned long empty_zero_page, zero_page_mask;
 EXPORT_SYMBOL(empty_zero_page);
+EXPORT_SYMBOL(zero_page_mask);
 
 static void __init setup_zero_pages(void)
 {
diff --git a/mm/memory.c b/mm/memory.c
index a0c9c6cb59d1..f5744269a454 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -116,6 +116,8 @@ __setup("norandmaps", disable_randmaps);
 unsigned long zero_pfn __read_mostly;
 unsigned long highest_memmap_pfn __read_mostly;
 
+EXPORT_SYMBOL(zero_pfn);
+
 /*
  * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
  */
-- 
2.10.2