3.11-rc7 big endian - atags and bootloader updates

3.11-rc7 big endian - atags and bootloader updates

[Ben Dooks]

This series is to better support older bootloaders, especially the
ones that still pass some information in the ATAGS structure used
by pre-fdt booting. The series is available at:

	git://git.baserock.org/delta/linux baserock/311-rc7/be/atags-v2

[PATCH 1/5] ARM: add CPU_BE8_BOOT_LE configuration

[Ben Dooks]

Add configuration for booting a BE8 system from a LE boot environment.

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
---
 arch/arm/mm/Kconfig |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 1f8fed9..8b89ca1 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -712,6 +712,13 @@ config CPU_ENDIAN_BE8
 	help
 	  Support for the BE-8 (big-endian) mode on ARMv6 and ARMv7 processors.
 
+config CPU_BE8_BOOT_LE
+	bool "Boot BE system from LE loader"
+	depends on CPU_ENDIAN_BE8
+	help
+	  Support for running BE-8 (big-endian) from a boot environment that is
+	  running in LE mode.
+
 config CPU_ENDIAN_BE32
 	bool
 	depends on CPU_BIG_ENDIAN
-- 
1.7.10.4

[PATCH 2/5] ARM: fixup head for atag verification

[Ben Dooks]

If we booted LE but running BE8, ensure we read ATAGs data from head code
in the correct mode.

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
---
 arch/arm/kernel/head-common.S |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
index 47cd974..94e0434 100644
--- a/arch/arm/kernel/head-common.S
+++ b/arch/arm/kernel/head-common.S
@@ -21,6 +21,12 @@
 #define OF_DT_MAGIC 0xedfe0dd0 /* 0xd00dfeed in big-endian */
 #endif
 
+#ifdef CONFIG_CPU_BE8_BOOT_LE
+#define BE8_LE(x...)	x
+#else
+#define BE8_LE(x...)
+#endif
+
 /*
  * Exception handling.  Something went wrong and we can't proceed.  We
  * ought to tell the user, but since we don't have any guarantee that
@@ -53,10 +59,12 @@ __vet_atags:
 	cmp	r5, r6
 	beq	2f
 #endif
+BE8_LE(	rev	r5, r5 )
 	cmp	r5, #ATAG_CORE_SIZE		@ is first tag ATAG_CORE?
 	cmpne	r5, #ATAG_CORE_SIZE_EMPTY
 	bne	1f
 	ldr	r5, [r2, #4]
+BE8_LE(	rev	r5, r5 )
 	ldr	r6, =ATAG_CORE
 	cmp	r5, r6
 	bne	1f
-- 
1.7.10.4

[PATCH 3/5] ARM: add atag32_to_cpu() function

[Ben Dooks]

Add atag32_to_cpu() function to allow code manipulating ATAGs to deal
with the case where the boot-loader was in little-endian and Linux is
running big-endian.

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
---
 arch/arm/include/uapi/asm/setup.h |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/uapi/asm/setup.h b/arch/arm/include/uapi/asm/setup.h
index 979ff40..d3b3fa1 100644
--- a/arch/arm/include/uapi/asm/setup.h
+++ b/arch/arm/include/uapi/asm/setup.h
@@ -175,13 +175,20 @@ struct tagtable {
 
 #define tag_member_present(tag,member)				\
 	((unsigned long)(&((struct tag *)0L)->member + 1)	\
-		<= (tag)->hdr.size * 4)
+		<= atag32_to_cpu((tag)->hdr.size) * 4)
 
-#define tag_next(t)	((struct tag *)((__u32 *)(t) + (t)->hdr.size))
+#define tag_next(t)	((struct tag *)((__u32 *)(t) + atag32_to_cpu((t)->hdr.size)))
 #define tag_size(type)	((sizeof(struct tag_header) + sizeof(struct type)) >> 2)
 
 #define for_each_tag(t,base)		\
 	for (t = base; t->hdr.size; t = tag_next(t))
 
+#ifdef CONFIG_CPU_BE8_BOOT_LE
+#define atag32_to_cpu(x)	le32_to_cpu(x)
+#define cpu_to_atag32(x)	cpu_to_le32(x)
+#else
+#define	cpu_to_atag32(x)	x
+#define atag32_to_cpu(x)	x
+#endif
 
 #endif /* _UAPI__ASMARM_SETUP_H */
-- 
1.7.10.4

[PATCH 4/5] ARM: update atag-to-fdt code to be endian agnostic

[Ben Dooks]

The atag-to-fdt code can now use the conversion function we introduced
previously to avoid it having to know about the endian-ness of the
environment which booted the processor.

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
---
 arch/arm/boot/compressed/atags_to_fdt.c |   27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/arch/arm/boot/compressed/atags_to_fdt.c b/arch/arm/boot/compressed/atags_to_fdt.c
index d1153c8..1e094ea 100644
--- a/arch/arm/boot/compressed/atags_to_fdt.c
+++ b/arch/arm/boot/compressed/atags_to_fdt.c
@@ -121,9 +121,9 @@ int atags_to_fdt(void *atag_list, void *fdt, int total_space)
 	       return 0;
 
 	/* validate the ATAG */
-	if (atag->hdr.tag != ATAG_CORE ||
-	    (atag->hdr.size != tag_size(tag_core) &&
-	     atag->hdr.size != 2))
+	if (atag->hdr.tag != cpu_to_atag32(ATAG_CORE) ||
+	    (atag->hdr.size != cpu_to_atag32(tag_size(tag_core)) &&
+	     atag->hdr.size != cpu_to_atag32(2)))
 		return 1;
 
 	/* let's give it all the room it could need */
@@ -132,7 +132,7 @@ int atags_to_fdt(void *atag_list, void *fdt, int total_space)
 		return ret;
 
 	for_each_tag(atag, atag_list) {
-		if (atag->hdr.tag == ATAG_CMDLINE) {
+		if (atag->hdr.tag == cpu_to_atag32(ATAG_CMDLINE)) {
 			/* Append the ATAGS command line to the device tree
 			 * command line.
 			 * NB: This means that if the same parameter is set in
@@ -145,11 +145,12 @@ int atags_to_fdt(void *atag_list, void *fdt, int total_space)
 			else
 				setprop_string(fdt, "/chosen", "bootargs",
 					       atag->u.cmdline.cmdline);
-		} else if (atag->hdr.tag == ATAG_MEM) {
+		} else if (atag->hdr.tag == cpu_to_atag32(ATAG_MEM)) {
 			if (memcount >= sizeof(mem_reg_property)/4)
 				continue;
-			if (!atag->u.mem.size)
+			if (!atag32_to_cpu(atag->u.mem.size))
 				continue;
+
 			memsize = get_cell_size(fdt);
 
 			if (memsize == 2) {
@@ -159,20 +160,20 @@ int atags_to_fdt(void *atag_list, void *fdt, int total_space)
 				uint64_t *mem_reg_prop64 =
 					(uint64_t *)mem_reg_property;
 				mem_reg_prop64[memcount++] =
-					cpu_to_fdt64(atag->u.mem.start);
+					cpu_to_fdt64(atag32_to_cpu(atag->u.mem.start));
 				mem_reg_prop64[memcount++] =
-					cpu_to_fdt64(atag->u.mem.size);
+						     cpu_to_fdt64(atag32_to_cpu(atag->u.mem.size));
 			} else {
 				mem_reg_property[memcount++] =
-					cpu_to_fdt32(atag->u.mem.start);
+					cpu_to_fdt32(atag32_to_cpu(atag->u.mem.start));
 				mem_reg_property[memcount++] =
-					cpu_to_fdt32(atag->u.mem.size);
+					cpu_to_fdt32(atag32_to_cpu(atag->u.mem.size));
 			}
 
-		} else if (atag->hdr.tag == ATAG_INITRD2) {
+		} else if (atag->hdr.tag == cpu_to_atag32(ATAG_INITRD2)) {
 			uint32_t initrd_start, initrd_size;
-			initrd_start = atag->u.initrd.start;
-			initrd_size = atag->u.initrd.size;
+			initrd_start = atag32_to_cpu(atag->u.initrd.start);
+			initrd_size = atag32_to_cpu(atag->u.initrd.size);
 			setprop_cell(fdt, "/chosen", "linux,initrd-start",
 					initrd_start);
 			setprop_cell(fdt, "/chosen", "linux,initrd-end",
-- 
1.7.10.4

[PATCH 5/5] ARM: ensure loader information in LE format for BE kernels

[Ben Dooks]

From: Nico Pitre <nico@fluxnic.net>

If the loader for the system is assuming we are booting a BE kernel
from a LE loading environment, then ensure that the magic number
and image start/end values are in little endian format.

[ben.dooks at codethink.co.uk: from nico's original email on this subject]
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
---
 arch/arm/boot/compressed/Makefile       |    5 ++++-
 arch/arm/boot/compressed/head.S         |    7 ++++---
 arch/arm/boot/compressed/vmlinux.lds.in |   14 ++++++++++++++
 3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index 7ac1610..7c5634c 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -196,8 +196,11 @@ CFLAGS_font.o := -Dstatic=
 $(obj)/font.c: $(FONTC)
 	$(call cmd,shipped)
 
-$(obj)/vmlinux.lds: $(obj)/vmlinux.lds.in arch/arm/boot/Makefile $(KCONFIG_CONFIG)
+$(obj)/vmlinux.lds.S: $(obj)/vmlinux.lds.in arch/arm/boot/Makefile $(KCONFIG_CONFIG)
 	@sed "$(SEDFLAGS)" < $< > $@
 
+$(obj)/vmlinux.lds: $(obj)/vmlinux.lds.S
+	$(call if_changed,cpp_lds_S)
+
 $(obj)/hyp-stub.S: $(srctree)/arch/$(SRCARCH)/kernel/hyp-stub.S
 	$(call cmd,shipped)
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index 066b034..8ea1773 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -130,9 +130,10 @@ start:
  THUMB(		adr	r12, BSYM(1f)	)
  THUMB(		bx	r12		)
 
-		.word	0x016f2818		@ Magic numbers to help the loader
-		.word	start			@ absolute load/run zImage address
-		.word	_edata			@ zImage end address
+		.word	_magic_sig	@ Magic numbers to help the loader
+		.word	_magic_start	@ absolute load/run zImage address
+		.word	_magic_end	@ zImage end address
+
  THUMB(		.thumb			)
 1:
  ARM_BE8(	setend	be )			@ go BE8 if compiled for BE8
diff --git a/arch/arm/boot/compressed/vmlinux.lds.in b/arch/arm/boot/compressed/vmlinux.lds.in
index 4919f2a..567250f 100644
--- a/arch/arm/boot/compressed/vmlinux.lds.in
+++ b/arch/arm/boot/compressed/vmlinux.lds.in
@@ -7,6 +7,16 @@
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
+
+#ifdef CONFIG_CPU_BE8_BOOT_LE
+#define ZIMAGE_MAGIC(x) ( (((x) >> 24) & 0x000000ff) | \
+			  (((x) >>  8) & 0x0000ff00) | \
+			  (((x) <<  8) & 0x00ff0000) | \
+			  (((x) << 24) & 0xff000000) )
+#else
+#define ZIMAGE_MAGIC(x) (x)
+#endif
+
 OUTPUT_ARCH(arm)
 ENTRY(_start)
 SECTIONS
@@ -57,6 +67,10 @@ SECTIONS
   .pad			: { BYTE(0); . = ALIGN(8); }
   _edata = .;
 
+  _magic_sig = ZIMAGE_MAGIC(0x016f2818);
+  _magic_start = ZIMAGE_MAGIC(_start);
+  _magic_end = ZIMAGE_MAGIC(_edata);
+
   . = BSS_START;
   __bss_start = .;
   .bss			: { *(.bss) }
-- 
1.7.10.4

3.11-rc7 big endian - atags and bootloader updates

[Ben Dooks]

On 03/09/13 11:40, Dave Martin wrote:
> On Fri, Aug 30, 2013 at 08:17:56PM +0100, Ben Dooks wrote:
>> This series is to better support older bootloaders, especially the
>> ones that still pass some information in the ATAGS structure used
>> by pre-fdt booting. The series is available at:
>>
>> 	git://git.baserock.org/delta/linux baserock/311-rc7/be/atags-v2
>
> This seems a good idea, but it is a change to the boot protocol which
> may break any existing BE bootloader today.  Are you sure this won't
> cause problems for anyone?

You have to manually select it, so not really.

> One partial solution could be to make the ATAGs endianness-agnostic.
>
> Since the ATAGs start with ATAG core, we know that the word at offset
> <atags base + 4>  must have the value 0x54410001.  If we see a backwards
> value, we know the ATAGs are wrong-endian and every word must must be
> swabbed.

That would be possible, I will look into that.

> What to do about the zImage magic is less clear.  Up to this point,
> BE kernels have always had backwards magic.  Changing the magic might
> upset existing bootloaders, but I've never used a BE be bootloader, so
> I can't really comment on that...

This series uses a specific configuration to change both the ATAG
and magic if the system is meant to be big-endian, but booted on
a little-endian system.

>
> Documentation/arm/Booting should also be updated to reflect any change.
> In fact, what's already there could use clarification, since there is
> no statement about endianness at all yet.

Ok, good idea.


-- 
Ben Dooks				http://www.codethink.co.uk/
Senior Engineer				Codethink - Providing Genius