linux-kernel - [PATCH 07/10] x86: make TASK_SIZE

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Date:   Thu, 27 Aug 2020 17:00:27 +0200
From:   Christoph Hellwig <hch@....de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Michael Ellerman <mpe@...erman.id.au>, x86@...nel.org
Cc:     Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-arch@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 07/10] x86: make TASK_SIZE_MAX usable from assembly code

For 64-bit the only thing missing was a strategic _AC, and for 32-bit we
need to use __PAGE_OFFSET instead of PAGE_OFFSET in the TASK_SIZE
definition to escape the explicit unsigned long cast.  This just works
because __PAGE_OFFSET is defined using _AC itself and thus never needs
the cast anyway.

Signed-off-by: Christoph Hellwig <hch@....de>
Reviewed-by: Kees Cook <keescook@...omium.org>
---
 arch/x86/include/asm/page_32_types.h | 4 ++--
 arch/x86/include/asm/page_64_types.h | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/page_32_types.h b/arch/x86/include/asm/page_32_types.h
index 26236925fb2c36..f462895a33e452 100644
--- a/arch/x86/include/asm/page_32_types.h
+++ b/arch/x86/include/asm/page_32_types.h
@@ -44,8 +44,8 @@
 /*
  * User space process size: 3GB (default).
  */
-#define IA32_PAGE_OFFSET	PAGE_OFFSET
-#define TASK_SIZE		PAGE_OFFSET
+#define IA32_PAGE_OFFSET	__PAGE_OFFSET
+#define TASK_SIZE		__PAGE_OFFSET
 #define TASK_SIZE_LOW		TASK_SIZE
 #define TASK_SIZE_MAX		TASK_SIZE
 #define DEFAULT_MAP_WINDOW	TASK_SIZE
diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
index 996595c9897e0a..838515daf87b36 100644
--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -76,7 +76,7 @@
  *
  * With page table isolation enabled, we map the LDT in ... [stay tuned]
  */
-#define TASK_SIZE_MAX	((1UL << __VIRTUAL_MASK_SHIFT) - PAGE_SIZE)
+#define TASK_SIZE_MAX	((_AC(1,UL) << __VIRTUAL_MASK_SHIFT) - PAGE_SIZE)
 
 #define DEFAULT_MAP_WINDOW	((1UL << 47) - PAGE_SIZE)
 
-- 
2.28.0