[U-Boot] [PATCH 1/2] ARMv8: add optional Linux kernel image header

[U-Boot] [PATCH 1/2] ARMv8: add optional Linux kernel image header

[Stephen Warren]

From: Stephen Warren <swarren@nvidia.com>

Allow placing a Linux kernel image header at the start of the U-Boot
binary. This is useful since the image header reports the amount of memory
(BSS and similar) that U-Boot needs to use, but that isn't part of the
binary size. This can be used by the code that loads U-Boot into memory to
determine where to load U-Boot, based on other users of memory.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
---
This series relies (at the very least for diff context) on the previous
series I sent Dec 19: ARM: tegra: don't use CONFIG_SPL_TEXT_BASE when no
SPL ... ARM: tegra: use CONFIG_SYS_INIT_SP_BSS_OFFSET.

 arch/arm/Kconfig                                   | 16 ++++
 .../arm/cpu/armv8/linux-kernel-image-header-vars.h | 86 ++++++++++++++++++++++
 arch/arm/cpu/armv8/start.S                         |  4 +-
 arch/arm/cpu/armv8/u-boot.lds                      |  4 +
 arch/arm/include/asm/boot0-linux-kernel-header.h   | 49 ++++++++++++
 5 files changed, 158 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm/cpu/armv8/linux-kernel-image-header-vars.h
 create mode 100644 arch/arm/include/asm/boot0-linux-kernel-header.h

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 93b93c142929..69f304b6d7e6 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -32,6 +32,22 @@ config SYS_INIT_SP_BSS_OFFSET
 	  calculate the stack pointer. This offset should be large enough so
 	  that the early malloc region, global data (gd), and early stack usage
 	  do not overlap any appended DTB.
+
+config LINUX_KERNEL_IMAGE_HEADER
+	bool
+	help
+	  Place a Linux kernel image header at the start of the U-Boot binary.
+	  This is useful since the image header reports the amount of memory
+	  (BSS and similar) that U-Boot needs to use, but that isn't part of
+	  the binary size.
+
+if LINUX_KERNEL_IMAGE_HEADER
+config LNX_KRNL_IMG_TEXT_OFFSET_BASE
+	hex
+	help
+	  The value subtracted from CONFIG_SYS_TEXT_BASE to calculate the
+	  TEXT_OFFSET value written in to the Linux kernel image header.
+endif
 endif
 
 config STATIC_RELA
diff --git a/arch/arm/cpu/armv8/linux-kernel-image-header-vars.h b/arch/arm/cpu/armv8/linux-kernel-image-header-vars.h
new file mode 100644
index 000000000000..3e720937f012
--- /dev/null
+++ b/arch/arm/cpu/armv8/linux-kernel-image-header-vars.h
@@ -0,0 +1,86 @@
+/*
+ * (C) Copyright 2017 NVIDIA Corporation <www.nvidia.com>
+ *
+ * Derived from Linux kernel v4.14 files:
+ *
+ * arch/arm64/include/asm/assembler.h:
+ * Based on arch/arm/include/asm/assembler.h, arch/arm/mm/proc-macros.S
+ * Copyright (C) 1996-2000 Russell King
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * arch/arm64/kernel/head.S:
+ * Based on arch/arm/kernel/head.S
+ * Copyright (C) 1994-2002 Russell King
+ * Copyright (C) 2003-2012 ARM Ltd.
+ * Authors:	Catalin Marinas <catalin.marinas@arm.com>
+ *		Will Deacon <will.deacon@arm.com>
+ *
+ * arch/arm64/kernel/image.h:
+ * Copyright (C) 2014 ARM Ltd.
+ *
+ * SPDX-License-Identifier:     GPL-2.0
+ */
+
+/*
+ * There aren't any ELF relocations we can use to endian-swap values known only
+ * at link time (e.g. the subtraction of two symbol addresses), so we must get
+ * the linker to endian-swap certain values before emitting them.
+ *
+ * Note that, in order for this to work when building the ELF64 PIE executable
+ * (for KASLR), these values should not be referenced via R_AARCH64_ABS64
+ * relocations, since these are fixed up at runtime rather than at build time
+ * when PIE is in effect. So we need to split them up in 32-bit high and low
+ * words.
+ */
+#ifdef CONFIG_CPU_BIG_ENDIAN
+#define DATA_LE32(data)				\
+	((((data) & 0x000000ff) << 24) |	\
+	 (((data) & 0x0000ff00) << 8)  |	\
+	 (((data) & 0x00ff0000) >> 8)  |	\
+	 (((data) & 0xff000000) >> 24))
+#else
+#define DATA_LE32(data) ((data) & 0xffffffff)
+#endif
+
+#define DEFINE_IMAGE_LE64(sym, data)				\
+	sym##_lo32 = DATA_LE32((data) & 0xffffffff);		\
+	sym##_hi32 = DATA_LE32((data) >> 32)
+
+#define __MAX(a, b)		(((a) > (b)) ? (a) : (b))
+#define __CODE_DATA_SIZE	(__bss_start - _start)
+#define __BSS_SIZE		(__bss_end - __bss_start)
+#ifdef CONFIG_SYS_INIT_SP_BSS_OFFSET
+#define __MAX_EXTRA_RAM_USAGE	__MAX(__BSS_SIZE, CONFIG_SYS_INIT_SP_BSS_OFFSET)
+#else
+#define __MAX_EXTRA_RAM_USAGE	__BSS_SIZE
+#endif
+#define __MEM_USAGE		(__CODE_DATA_SIZE + __MAX_EXTRA_RAM_USAGE)
+
+#ifdef CONFIG_CPU_BIG_ENDIAN
+#define __HEAD_FLAG_BE		1
+#else
+#define __HEAD_FLAG_BE		0
+#endif
+
+#define __HEAD_FLAG_PAGE_SIZE	1 /* 4K hard-coded */
+
+#define __HEAD_FLAG_PHYS_BASE	1
+
+#define __HEAD_FLAGS		((__HEAD_FLAG_BE << 0) |	\
+				 (__HEAD_FLAG_PAGE_SIZE << 1) |	\
+				 (__HEAD_FLAG_PHYS_BASE << 3))
+
+#define TEXT_OFFSET (CONFIG_SYS_TEXT_BASE - \
+			CONFIG_LNX_KRNL_IMG_TEXT_OFFSET_BASE)
+
+/*
+ * These will output as part of the Image header, which should be little-endian
+ * regardless of the endianness of the kernel. While constant values could be
+ * endian swapped in head.S, all are done here for consistency.
+ */
+#define HEAD_SYMBOLS						\
+	DEFINE_IMAGE_LE64(_kernel_size_le, __MEM_USAGE);	\
+	DEFINE_IMAGE_LE64(_kernel_offset_le, TEXT_OFFSET);	\
+	DEFINE_IMAGE_LE64(_kernel_flags_le, __HEAD_FLAGS);
+
+	HEAD_SYMBOLS
diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S
index 03e744e4a673..7c6807f4e1fd 100644
--- a/arch/arm/cpu/armv8/start.S
+++ b/arch/arm/cpu/armv8/start.S
@@ -19,7 +19,9 @@
 
 .globl	_start
 _start:
-#ifdef CONFIG_ENABLE_ARM_SOC_BOOT0_HOOK
+#if defined(LINUX_KERNEL_IMAGE_HEADER)
+#include <asm/boot0-linux-kernel-header.h>
+#elif defined(CONFIG_ENABLE_ARM_SOC_BOOT0_HOOK)
 /*
  * Various SoCs need something special and SoC-specific up front in
  * order to boot, allow them to set that in their boot0.h file and then
diff --git a/arch/arm/cpu/armv8/u-boot.lds b/arch/arm/cpu/armv8/u-boot.lds
index 22195b8834b5..7b76e0f9f08e 100644
--- a/arch/arm/cpu/armv8/u-boot.lds
+++ b/arch/arm/cpu/armv8/u-boot.lds
@@ -159,4 +159,8 @@ SECTIONS
 	/DISCARD/ : { *(.plt*) }
 	/DISCARD/ : { *(.interp*) }
 	/DISCARD/ : { *(.gnu*) }
+
+#ifdef CONFIG_LINUX_KERNEL_IMAGE_HEADER
+#include "linux-kernel-image-header-vars.h"
+#endif
 }
diff --git a/arch/arm/include/asm/boot0-linux-kernel-header.h b/arch/arm/include/asm/boot0-linux-kernel-header.h
new file mode 100644
index 000000000000..ca28780daac5
--- /dev/null
+++ b/arch/arm/include/asm/boot0-linux-kernel-header.h
@@ -0,0 +1,49 @@
+/*
+ * (C) Copyright 2017 NVIDIA Corporation <www.nvidia.com>
+ *
+ * Derived from Linux kernel v4.14 files:
+ *
+ * arch/arm64/include/asm/assembler.h:
+ * Based on arch/arm/include/asm/assembler.h, arch/arm/mm/proc-macros.S
+ * Copyright (C) 1996-2000 Russell King
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * arch/arm64/kernel/head.S:
+ * Based on arch/arm/kernel/head.S
+ * Copyright (C) 1994-2002 Russell King
+ * Copyright (C) 2003-2012 ARM Ltd.
+ * Authors:	Catalin Marinas <catalin.marinas@arm.com>
+ *		Will Deacon <will.deacon@arm.com>
+ *
+ * arch/arm64/kernel/image.h:
+ * Copyright (C) 2014 ARM Ltd.
+ *
+ * SPDX-License-Identifier:     GPL-2.0
+ */
+
+	/*
+	 * Emit a 64-bit absolute little endian symbol reference in a way that
+	 * ensures that it will be resolved at build time, even when building a
+	 * PIE binary. This requires cooperation from the linker script, which
+	 * must emit the lo32/hi32 halves individually.
+	 */
+	.macro	le64sym, sym
+	.long	\sym\()_lo32
+	.long	\sym\()_hi32
+	.endm
+
+.globl _start
+_start:
+	/*
+	 * DO NOT MODIFY. Image header expected by Linux boot-loaders.
+	 */
+	b	reset				/* branch to kernel start, magic */
+	.long	0				/* reserved */
+	le64sym	_kernel_offset_le		/* Image load offset from start of RAM, little-endian */
+	le64sym	_kernel_size_le			/* Effective size of kernel image, little-endian */
+	le64sym	_kernel_flags_le		/* Informative flags, little-endian */
+	.quad	0				/* reserved */
+	.quad	0				/* reserved */
+	.quad	0				/* reserved */
+	.ascii	"ARM\x64"			/* Magic number */
+	.long	0				/* reserved */
-- 
2.15.1

[U-Boot] [PATCH 2/2] ARM: tegra: use LINUX_KERNEL_IMAGE_HEADER

[Stephen Warren]

From: Stephen Warren <swarren@nvidia.com>

Enable CONFIG_LINUX_KERNEL_IMAGE_HEADER for all 64-bit Tegra boards.
cboot (the boot SW that runs before U-Boot) will eventually use this
information.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
---
 arch/arm/mach-tegra/Kconfig | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm/mach-tegra/Kconfig b/arch/arm/mach-tegra/Kconfig
index 51d143687b06..fd0082d22a33 100644
--- a/arch/arm/mach-tegra/Kconfig
+++ b/arch/arm/mach-tegra/Kconfig
@@ -60,8 +60,14 @@ config TEGRA_ARMV7_COMMON
 config TEGRA_ARMV8_COMMON
 	bool "Tegra 64-bit common options"
 	select ARM64
+	select LINUX_KERNEL_IMAGE_HEADER
 	select TEGRA_COMMON
 
+if TEGRA_ARMV8_COMMON
+config LNX_KRNL_IMG_TEXT_OFFSET_BASE
+	default 0x80000000
+endif
+
 choice
 	prompt "Tegra SoC select"
 	optional
-- 
2.15.1

[U-Boot] [PATCH 1/2] ARMv8: add optional Linux kernel image header

[Tom Rini]

On Tue, Jan 02, 2018 at 04:54:21PM -0700, Stephen Warren wrote:

> From: Stephen Warren <swarren@nvidia.com>
> 
> Allow placing a Linux kernel image header at the start of the U-Boot
> binary. This is useful since the image header reports the amount of memory
> (BSS and similar) that U-Boot needs to use, but that isn't part of the
> binary size. This can be used by the code that loads U-Boot into memory to
> determine where to load U-Boot, based on other users of memory.
> 
> Signed-off-by: Stephen Warren <swarren@nvidia.com>
> ---
> This series relies (at the very least for diff context) on the previous
> series I sent Dec 19: ARM: tegra: don't use CONFIG_SPL_TEXT_BASE when no
> SPL ... ARM: tegra: use CONFIG_SYS_INIT_SP_BSS_OFFSET.

Neat.  Are the Linux folks encouraging other projects to re-use this
header?  Is there somewhere we can point to as reference for the format
for the Kconfig help as well, not just the text?  Thanks!

-- 
Tom
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[U-Boot] [PATCH 1/2] ARMv8: add optional Linux kernel image header

[Stephen Warren]

On 01/03/2018 06:45 AM, Tom Rini wrote:
> On Tue, Jan 02, 2018 at 04:54:21PM -0700, Stephen Warren wrote:
> 
>> From: Stephen Warren <swarren@nvidia.com>
>>
>> Allow placing a Linux kernel image header at the start of the U-Boot
>> binary. This is useful since the image header reports the amount of memory
>> (BSS and similar) that U-Boot needs to use, but that isn't part of the
>> binary size. This can be used by the code that loads U-Boot into memory to
>> determine where to load U-Boot, based on other users of memory.
>>
>> Signed-off-by: Stephen Warren <swarren@nvidia.com>
>> ---
>> This series relies (at the very least for diff context) on the previous
>> series I sent Dec 19: ARM: tegra: don't use CONFIG_SPL_TEXT_BASE when no
>> SPL ... ARM: tegra: use CONFIG_SYS_INIT_SP_BSS_OFFSET.
> 
> Neat.  Are the Linux folks encouraging other projects to re-use this
> header?

Not that I'm aware of, but mainly because I haven't talked to upstream 
kernel people about this at all. I implemented this because in recent 
versions of Linux4Tegra, for all 64-bit SoCs, our main CPU EL2/EL1 boot 
path is either:

cboot -> Linux kernel
cboot -> U-Boot -> Linux kernel

cboot is an NVIDIA binary bootloader. cboot wants to know about BSS/... 
usage of the binary it loads, which can be determined from the Linux 
kernel image header, but we don't want cboot to take different paths 
when booting Linux or U-Boot (or indeed anything at all), so the 
simplest thing was to make U-Boot look as identical to a Linux kernel as 
possible.

> Is there somewhere we can point to as reference for the format
> for the Kconfig help as well, not just the text?  Thanks!

The Linux kernel file Documentation/arm64/booting.txt does describe the 
format. Should I respin and add that filename to the Kconfig text?

[U-Boot] [PATCH 1/2] ARMv8: add optional Linux kernel image header

[Tom Rini]

On Wed, Jan 03, 2018 at 10:42:56AM -0700, Stephen Warren wrote:
> On 01/03/2018 06:45 AM, Tom Rini wrote:
> >On Tue, Jan 02, 2018 at 04:54:21PM -0700, Stephen Warren wrote:
> >
> >>From: Stephen Warren <swarren@nvidia.com>
> >>
> >>Allow placing a Linux kernel image header at the start of the U-Boot
> >>binary. This is useful since the image header reports the amount of memory
> >>(BSS and similar) that U-Boot needs to use, but that isn't part of the
> >>binary size. This can be used by the code that loads U-Boot into memory to
> >>determine where to load U-Boot, based on other users of memory.
> >>
> >>Signed-off-by: Stephen Warren <swarren@nvidia.com>
> >>---
> >>This series relies (at the very least for diff context) on the previous
> >>series I sent Dec 19: ARM: tegra: don't use CONFIG_SPL_TEXT_BASE when no
> >>SPL ... ARM: tegra: use CONFIG_SYS_INIT_SP_BSS_OFFSET.
> >
> >Neat.  Are the Linux folks encouraging other projects to re-use this
> >header?
> 
> Not that I'm aware of, but mainly because I haven't talked to upstream
> kernel people about this at all. I implemented this because in recent
> versions of Linux4Tegra, for all 64-bit SoCs, our main CPU EL2/EL1 boot path
> is either:
> 
> cboot -> Linux kernel
> cboot -> U-Boot -> Linux kernel
> 
> cboot is an NVIDIA binary bootloader. cboot wants to know about BSS/...
> usage of the binary it loads, which can be determined from the Linux kernel
> image header, but we don't want cboot to take different paths when booting
> Linux or U-Boot (or indeed anything at all), so the simplest thing was to
> make U-Boot look as identical to a Linux kernel as possible.
> 
> >Is there somewhere we can point to as reference for the format
> >for the Kconfig help as well, not just the text?  Thanks!
> 
> The Linux kernel file Documentation/arm64/booting.txt does describe the
> format. Should I respin and add that filename to the Kconfig text?

Yes, and I feel like it can't hurt to let the arm64 maintainers know too
as frankly it's a good idea and more projects should make use of it, so
maybe it should be a bit more formally documented (in one of those fancy
new rst files?) or something.

-- 
Tom
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[U-Boot] [PATCH 1/2] ARMv8: add optional Linux kernel image header

[Stephen Warren]

On 01/03/2018 10:56 AM, Tom Rini wrote:
> On Wed, Jan 03, 2018 at 10:42:56AM -0700, Stephen Warren wrote:
>> On 01/03/2018 06:45 AM, Tom Rini wrote:
>>> On Tue, Jan 02, 2018 at 04:54:21PM -0700, Stephen Warren wrote:
>>>
>>>> From: Stephen Warren <swarren@nvidia.com>
>>>>
>>>> Allow placing a Linux kernel image header at the start of the U-Boot
>>>> binary. This is useful since the image header reports the amount of memory
>>>> (BSS and similar) that U-Boot needs to use, but that isn't part of the
>>>> binary size. This can be used by the code that loads U-Boot into memory to
>>>> determine where to load U-Boot, based on other users of memory.
>>>>
>>>> Signed-off-by: Stephen Warren <swarren@nvidia.com>
>>>> ---
>>>> This series relies (at the very least for diff context) on the previous
>>>> series I sent Dec 19: ARM: tegra: don't use CONFIG_SPL_TEXT_BASE when no
>>>> SPL ... ARM: tegra: use CONFIG_SYS_INIT_SP_BSS_OFFSET.
>>>
>>> Neat.  Are the Linux folks encouraging other projects to re-use this
>>> header?
>>
>> Not that I'm aware of, but mainly because I haven't talked to upstream
>> kernel people about this at all. I implemented this because in recent
>> versions of Linux4Tegra, for all 64-bit SoCs, our main CPU EL2/EL1 boot path
>> is either:
>>
>> cboot -> Linux kernel
>> cboot -> U-Boot -> Linux kernel
>>
>> cboot is an NVIDIA binary bootloader. cboot wants to know about BSS/...
>> usage of the binary it loads, which can be determined from the Linux kernel
>> image header, but we don't want cboot to take different paths when booting
>> Linux or U-Boot (or indeed anything at all), so the simplest thing was to
>> make U-Boot look as identical to a Linux kernel as possible.
>>
>>> Is there somewhere we can point to as reference for the format
>>> for the Kconfig help as well, not just the text?  Thanks!
>>
>> The Linux kernel file Documentation/arm64/booting.txt does describe the
>> format. Should I respin and add that filename to the Kconfig text?
> 
> Yes, and I feel like it can't hurt to let the arm64 maintainers know too
> as frankly it's a good idea and more projects should make use of it, so
> maybe it should be a bit more formally documented (in one of those fancy
> new rst files?) or something.

I talked to Catalin Marinas (one of the arch/arm64 maintainers) on IRC 
and he said he didn't see any issue with this approach.

[U-Boot] [PATCH 2/2] ARM: tegra: use LINUX_KERNEL_IMAGE_HEADER

[Simon Glass]

Hi Stephen,

On 2 January 2018 at 16:54, Stephen Warren <swarren@wwwdotorg.org> wrote:
> From: Stephen Warren <swarren@nvidia.com>
>
> Enable CONFIG_LINUX_KERNEL_IMAGE_HEADER for all 64-bit Tegra boards.
> cboot (the boot SW that runs before U-Boot) will eventually use this
> information.

How does U-Boot use it? Does it not come from the FIT?

>
> Signed-off-by: Stephen Warren <swarren@nvidia.com>
> ---
>  arch/arm/mach-tegra/Kconfig | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/arch/arm/mach-tegra/Kconfig b/arch/arm/mach-tegra/Kconfig
> index 51d143687b06..fd0082d22a33 100644
> --- a/arch/arm/mach-tegra/Kconfig
> +++ b/arch/arm/mach-tegra/Kconfig
> @@ -60,8 +60,14 @@ config TEGRA_ARMV7_COMMON
>  config TEGRA_ARMV8_COMMON
>         bool "Tegra 64-bit common options"
>         select ARM64
> +       select LINUX_KERNEL_IMAGE_HEADER
>         select TEGRA_COMMON
>
> +if TEGRA_ARMV8_COMMON
> +config LNX_KRNL_IMG_TEXT_OFFSET_BASE
> +       default 0x80000000
> +endif
> +
>  choice
>         prompt "Tegra SoC select"
>         optional
> --
> 2.15.1
>

Regards,
Simon

[U-Boot] [PATCH 2/2] ARM: tegra: use LINUX_KERNEL_IMAGE_HEADER

[Stephen Warren]

On 01/07/2018 09:50 PM, Simon Glass wrote:
> Hi Stephen,
> 
> On 2 January 2018 at 16:54, Stephen Warren <swarren@wwwdotorg.org> wrote:
>> From: Stephen Warren <swarren@nvidia.com>
>>
>> Enable CONFIG_LINUX_KERNEL_IMAGE_HEADER for all 64-bit Tegra boards.
>> cboot (the boot SW that runs before U-Boot) will eventually use this
>> information.
> 
> How does U-Boot use it? Does it not come from the FIT?

U-Boot doesn't use the header itself. Rather, the header provides 
information (e.g. BSS usage) to whatever SW is loading U-Boot into RAM. 
We don't use FIT at all; I'd rather our boot flow not know about 
bootloader-specific data formats.