ARMv8: add optional Linux kernel image header

PATCH Superseded Stephen Warren 3 participants 8 messages Jan 2, 2018 – Jan 8, 2018

Subsystems (3)

Arm (32-bit) Arm sub-architectures Tegra architecture support

lore

Share & tools

lore

Stephen Warren

author

2018-01-02 23:54 UTC #0 lore raw

PATCH 1/2 ARMv8: add optional Linux kernel image header

From: Stephen Warren <[email protected]>

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 <[email protected]>

---
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

arch/arm/Kconfig +16 -0

index 93b93c142929..69f304b6d7e6 100644
@@ -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

arch/arm/cpu/armv8/linux-kernel-image-header-vars.h new file +86 -0

86 lines not on this page · raw message

arch/arm/cpu/armv8/start.S +3 -1

index 03e744e4a673..7c6807f4e1fd 100644
@@ -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

arch/arm/cpu/armv8/u-boot.lds +4 -0

index 22195b8834b5..7b76e0f9f08e 100644
@@ -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
 }

arch/arm/include/asm/boot0-linux-kernel-header.h new file +49 -0

49 lines not on this page · raw message

Signature · 1 line

2.15.1

Stephen Warren

author

2018-01-02 23:54 UTC #1 lore raw

PATCH 2/2 ARM: tegra: use LINUX_KERNEL_IMAGE_HEADER

From: Stephen Warren <[email protected]>

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 <[email protected]>

---
 arch/arm/mach-tegra/Kconfig | 6 ++++++
 1 file changed, 6 insertions(+)

arch/arm/mach-tegra/Kconfig +6 -0

index 51d143687b06..fd0082d22a33 100644
@@ -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

Signature · 1 line

2.15.1

Simon Glass

2018-01-08 04:50 UTC #2 lore raw

PATCH 2/2 ARM: tegra: use LINUX_KERNEL_IMAGE_HEADER

Hi Stephen,

Quoted 5 lines · Stephen Warren

From: Stephen Warren <[email protected]>
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?

Quoted 26 lines

Signed-off-by Stephen Warren <[email protected]>

---
 arch/arm/mach-tegra/Kconfig | 6 ++++++
 1 file changed, 6 insertions(+)

arch/arm/mach-tegra/Kconfig +6 -1

index 51d143687b06..fd0082d22a33 100644
@@ -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
--

Quoted 2 lines

2.15.1

Regards,
Simon

Stephen Warren

author

2018-01-08 18:23 UTC #3 lore raw

PATCH 2/2 ARM: tegra: use LINUX_KERNEL_IMAGE_HEADER

Quoted 10 lines · Simon Glass

Hi Stephen,
Quoted 5 lines · Stephen Warren
From: Stephen Warren <[email protected]>
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.

Tom Rini

2018-01-03 13:45 UTC #4 lore raw

PATCH 1/2 ARMv8: add optional Linux kernel image header

In reply to Stephen Warren

Quoted 8 lines · Stephen Warren

From: Stephen Warren <[email protected]>
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.

Quoted 5 lines

Signed-off-by Stephen Warren <[email protected]>
---
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!

Signature · 8 lines

Tom
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: not available
URL: <http://lists.denx.de/pipermail/u-boot/attachments/20180103/fd04853e/attachment.sig>

Stephen Warren

author

2018-01-03 17:42 UTC #5 lore raw

PATCH 1/2 ARMv8: add optional Linux kernel image header

Quoted 10 lines · Tom Rini

Quoted 8 lines · Stephen Warren
From: Stephen Warren <[email protected]>
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.

Quoted 8 lines

Quoted 5 lines
Signed-off-by Stephen Warren <[email protected]>
---
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.

Quoted 2 lines

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?

Tom Rini

2018-01-03 17:56 UTC #6 lore raw

PATCH 1/2 ARMv8: add optional Linux kernel image header

Quoted 34 lines · Stephen Warren

Quoted 10 lines · Tom Rini
Quoted 8 lines · Stephen Warren
From: Stephen Warren <[email protected]>
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.
Quoted 8 lines
Quoted 5 lines
Signed-off-by Stephen Warren <[email protected]>
---
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.

Quoted 5 lines

Quoted 2 lines
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.

Signature · 8 lines

Tom
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: not available
URL: <http://lists.denx.de/pipermail/u-boot/attachments/20180103/68583c20/attachment.sig>

Stephen Warren

author

2018-01-03 21:31 UTC #7 lore raw

PATCH 1/2 ARMv8: add optional Linux kernel image header

Quoted 38 lines · Tom Rini

Quoted 37 lines · Stephen Warren
Quoted 10 lines · Tom Rini
Quoted 8 lines · Stephen Warren
From: Stephen Warren <[email protected]>
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.
Quoted 8 lines
Quoted 5 lines
Signed-off-by Stephen Warren <[email protected]>
---
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.
Quoted 2 lines
Is there somewhere we can point to as reference for the format for the Kconfig help as well, not just the text? Thanks!

Quoted 7 lines

Quoted 2 lines
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.