[PATCH] ARM: proc-v7.S: Adjust stack address when XIP_KERNEL

When XIP_KERNEL is enabled, the virt to phys address translation for RAM
is not the same as the virt to phys address translation for .text.
The only way to know where physical RAM is located is to use
PLAT_PHYS_OFFSET.
The MACRO will be useful for other places where there is a similar problem.

Written by Nicolas Pitre

Signed-off-by: Chris Brandt <chris.brandt@renesas.com>
Signed-off-by: Nicolas Pitre <redacted>
---
 arch/arm/include/asm/memory.h | 8 ++++++++
 arch/arm/mm/proc-v7.S         | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index c79b57b..7dd2ab5 100644
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h

@@ -134,6 +134,14 @@
  */
 #define PLAT_PHYS_OFFSET	UL(CONFIG_PHYS_OFFSET)
 
+#ifdef CONFIG_XIP_KERNEL
+#define PHYS_OFFSET_FIXUP \
+	( XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR) - PAGE_OFFSET + \
+	  PLAT_PHYS_OFFSET - CONFIG_XIP_PHYS_ADDR )
+#else
+#define PHYS_OFFSET_FIXUP 0
+#endif
+
 #ifndef __ASSEMBLY__
 
 /*

diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 0f92d57..1595fb2 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S

@@ -487,7 +487,7 @@ __errata_finish:
 
 	.align	2
 __v7_setup_stack_ptr:
-	.word	__v7_setup_stack - .
+	.word	__v7_setup_stack - . + PHYS_OFFSET_FIXUP
 ENDPROC(__v7_setup)
 
 	.bss

-- 
1.9.1

On Friday 29 January 2016 17:11:14 Chris Brandt wrote:

When XIP_KERNEL is enabled, the virt to phys address translation for RAM
is not the same as the virt to phys address translation for .text.
The only way to know where physical RAM is located is to use
PLAT_PHYS_OFFSET.
The MACRO will be useful for other places where there is a similar problem.

Written by Nicolas Pitre

Signed-off-by: Chris Brandt <chris.brandt@renesas.com>
Signed-off-by: Nicolas Pitre <redacted>

I have not verified the contents of the patch, but have two comments on the
submission form:

- replace the 'Written by Nicolas Pitre' sentence with a 'From: Nicolas
  Pitre [off-list ref]' line as the first line of the changelog text,
  followed by an empty line, so that 'git am' can set the correct author
  field.

- put your Signed-off-by: line after Nico's for correct documentation
  of who sent what.

	Arnd

I have not verified the contents of the patch, but have two comments on the submission form:

- replace the 'Written by Nicolas Pitre' sentence with a 'From: Nicolas
  Pitre [off-list ref]' line as the first line of the changelog text,
  followed by an empty line, so that 'git am' can set the correct author
  field.

- put your Signed-off-by: line after Nico's for correct documentation
  of who sent what.

Arnd

OK, thank you. That makes more sense.


Chris

From: Nicolas Pitre <redacted>

When XIP_KERNEL is enabled, the virt to phys address translation for RAM
is not the same as the virt to phys address translation for .text.
The only way to know where physical RAM is located is to use
PLAT_PHYS_OFFSET.
The MACRO will be useful for other places where there is a similar problem.

Signed-off-by: Nicolas Pitre <redacted>
Signed-off-by: Chris Brandt <chris.brandt@renesas.com>
---
v2:
* Fixed Signed-off to show correct author
---
 arch/arm/include/asm/memory.h | 8 ++++++++
 arch/arm/mm/proc-v7.S         | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index c79b57b..7dd2ab5 100644
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h

@@ -134,6 +134,14 @@
  */
 #define PLAT_PHYS_OFFSET	UL(CONFIG_PHYS_OFFSET)
 
+#ifdef CONFIG_XIP_KERNEL
+#define PHYS_OFFSET_FIXUP \
+	( XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR) - PAGE_OFFSET + \
+	  PLAT_PHYS_OFFSET - CONFIG_XIP_PHYS_ADDR )
+#else
+#define PHYS_OFFSET_FIXUP 0
+#endif
+
 #ifndef __ASSEMBLY__
 
 /*

diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 0f92d57..1595fb2 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S

@@ -487,7 +487,7 @@ __errata_finish:
 
 	.align	2
 __v7_setup_stack_ptr:
-	.word	__v7_setup_stack - .
+	.word	__v7_setup_stack - . + PHYS_OFFSET_FIXUP
 ENDPROC(__v7_setup)
 
 	.bss

-- 
1.9.1

On Mon, 1 Feb 2016, Chris Brandt wrote:

From: Nicolas Pitre <redacted>

When XIP_KERNEL is enabled, the virt to phys address translation for RAM
is not the same as the virt to phys address translation for .text.
The only way to know where physical RAM is located is to use
PLAT_PHYS_OFFSET.
The MACRO will be useful for other places where there is a similar problem.

Signed-off-by: Nicolas Pitre <redacted>
Signed-off-by: Chris Brandt <chris.brandt@renesas.com>

Looks fine.  You may submit it here:

http://www.arm.linux.org.uk/developer/patches/

On Mon, Feb 01, 2016 at 04:15:38PM -0500, Nicolas Pitre wrote:

On Mon, 1 Feb 2016, Chris Brandt wrote:

quoted

From: Nicolas Pitre <redacted>

When XIP_KERNEL is enabled, the virt to phys address translation for RAM
is not the same as the virt to phys address translation for .text.
The only way to know where physical RAM is located is to use
PLAT_PHYS_OFFSET.
The MACRO will be useful for other places where there is a similar problem.

Signed-off-by: Nicolas Pitre <redacted>
Signed-off-by: Chris Brandt <chris.brandt@renesas.com>

Looks fine.  You may submit it here:

...

quoted

+#ifdef CONFIG_XIP_KERNEL
+#define PHYS_OFFSET_FIXUP \
+	( XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR) - PAGE_OFFSET + \
+	  PLAT_PHYS_OFFSET - CONFIG_XIP_PHYS_ADDR )
+#else
+#define PHYS_OFFSET_FIXUP 0
+#endif
+
 #ifndef __ASSEMBLY__
 
 /*

diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 0f92d57..1595fb2 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S

@@ -487,7 +487,7 @@ __errata_finish:
 
 	.align	2
 __v7_setup_stack_ptr:
-	.word	__v7_setup_stack - .
+	.word	__v7_setup_stack - . + PHYS_OFFSET_FIXUP

I keep looking at this patch, and I really find that I detest this
PHYS_OFFSET_FIXUP thing - it's really not obvious what's going on
here.  It's taken a _long_ time to work this out, which _really_
isn't good going forward.

Let's instead change things to make it much more obvious - see the
patch below.

diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index ebdaaf7dd19f..593e5613184d 100644
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h

@@ -135,11 +135,18 @@
 #define PLAT_PHYS_OFFSET	UL(CONFIG_PHYS_OFFSET)
 
 #ifdef CONFIG_XIP_KERNEL
-#define PHYS_OFFSET_FIXUP \
-	( XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR) - PAGE_OFFSET + \
-	  PLAT_PHYS_OFFSET - CONFIG_XIP_PHYS_ADDR )
+/*
+ * When referencing data in RAM from the XIP region in a relative manner
+ * with the MMU off, we need the relative offset between the two physical
+ * addresses.  The macro below achieves this, which is:
+ *    __pa(v_data) - __xip_pa(v_text)
+ */
+#define PHYS_RELATIVE(v_data, v_text) \
+	(((v_data) - PAGE_OFFSET + PLAT_PHYS_OFFSET) - \
+	 ((v_text) - XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR) + \
+          CONFIG_XIP_PHYS_ADDR))
 #else
-#define PHYS_OFFSET_FIXUP 0
+#define PHYS_RELATIVE(v_data, v_text) (v_data) - (v_text)
 #endif
 
 #ifndef __ASSEMBLY__

diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 1595fb29ec12..0f8963a7e7d9 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S

@@ -487,7 +487,7 @@ __errata_finish:
 
 	.align	2
 __v7_setup_stack_ptr:
-	.word	__v7_setup_stack - . + PHYS_OFFSET_FIXUP
+	.word	PHYS_RELATIVE(__v7_setup_stack, .)
 ENDPROC(__v7_setup)
 
 	.bss

-- 
RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
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On 16 Feb 2016, Russell King - ARM Linux wrote:

This works fine for me (comes up with the same number either way).

Just tested it with my XIP_KERNEL ARMv7 system.


Chris

On Tue, 16 Feb 2016, Russell King - ARM Linux wrote:

Sure, this is less opaque.

You should probably surround the whole thing with parents in case this 
gets used in some other computations.


Nicolas