linux-kernel - [PATCH] arm: get rid of hardcoded assumptions about kernel stack size

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Date:	Wed, 18 Jun 2014 17:50:22 +0400
From:	Andrey Ryabinin <a.ryabinin@...sung.com>
To:	Russell King <linux@....linux.org.uk>
Cc:	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Nicolas Pitre <nico@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Andrey Ryabinin <a.ryabinin@...sung.com>
Subject: [PATCH] arm: get rid of hardcoded assumptions about kernel stack size

Changing kernel stack size on arm is not as simple as it should be:
1) THRED_SIZE macro doen't respect PAGE_SIZE and THREAD_SIZE_ORDER
2) stack size is hardcoded in get_thread_info macro

This patch fixes it by caculating THREAD_SIZE and thread_info address
taking into account PAGE_SIZE and THREAD_SIZE_ORDER.

Now changing stack size becomes simply changing THREAD_SIZE_ORDER.

Signed-off-by: Andrey Ryabinin <a.ryabinin@...sung.com>
---
 arch/arm/include/asm/assembler.h   | 8 +++++---
 arch/arm/include/asm/thread_info.h | 3 ++-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
index 57f0584..906703a 100644
--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -24,6 +24,8 @@
 #include <asm/domain.h>
 #include <asm/opcodes-virt.h>
 #include <asm/asm-offsets.h>
+#include <asm/page.h>
+#include <asm/thread_info.h>
 
 #define IOMEM(x)	(x)
 
@@ -179,10 +181,10 @@
  * Get current thread_info.
  */
 	.macro	get_thread_info, rd
- ARM(	mov	\rd, sp, lsr #13	)
+ ARM(	mov	\rd, sp, lsr #THREAD_SIZE_ORDER + PAGE_SHIFT	)
  THUMB(	mov	\rd, sp			)
- THUMB(	lsr	\rd, \rd, #13		)
-	mov	\rd, \rd, lsl #13
+ THUMB(	lsr	\rd, \rd, #THREAD_SIZE_ORDER + PAGE_SHIFT	)
+	mov	\rd, \rd, lsl #THREAD_SIZE_ORDER + PAGE_SHIFT
 	.endm
 
 /*
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index f989d7c..f85d2b0 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -14,9 +14,10 @@
 
 #include <linux/compiler.h>
 #include <asm/fpstate.h>
+#include <asm/page.h>
 
 #define THREAD_SIZE_ORDER	1
-#define THREAD_SIZE		8192
+#define THREAD_SIZE		(PAGE_SIZE << THREAD_SIZE_ORDER)
 #define THREAD_START_SP		(THREAD_SIZE - 8)
 
 #ifndef __ASSEMBLY__
-- 
1.8.5.5

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