[U-Boot] [PATCH 1/2] ARMv8: add optional Linux kernel image header
Stephen Warren
swarren at wwwdotorg.org
Tue Jan 2 23:54:21 UTC 2018
From: Stephen Warren <swarren at 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 at 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 at arm.com>
+ * Will Deacon <will.deacon at 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 at arm.com>
+ * Will Deacon <will.deacon at 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
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