This patch provides the ability to boot using a device tree that is appended
to the raw binary Image (e.g. cat Image <filename>.dtb > Image_w_dtb).
Both BE and LE conditions are tested.
Got references from e2a6a3aa ("ARM: zImage: Allow the appending of a device
tree binary").
Signed-off-by: Yang Yingliang <yangyingli...@huawei.com>
---
arch/arm64/Kconfig | 11 +++++++++++
arch/arm64/kernel/head.S | 12 ++++++++++++
arch/arm64/kernel/vmlinux.lds.S | 17 +++++++++++++++++
3 files changed, 40 insertions(+)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 7796af4..d402448 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -660,6 +660,17 @@ endmenu
menu "Boot options"
+config ARM64_APPENDED_DTB
+ bool "Use appended device tree blob to Image"
+ depends on OF
+ help
+ With this option, the boot code will look for a device tree binary
+ (DTB) appended to Image
+ (e.g. cat Image <filename>.dtb > Image_w_dtb).
+
+ With this option, the size of Image will be extended to be 2MB
aligned.
+ The 2MB memory followed by Image is used for FDT blob.
+
config CMDLINE
string "Default kernel command string"
default ""
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 19f915e..ac00c8a 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -274,6 +274,18 @@ ENDPROC(preserve_boot_args)
* The dtb must be 8-byte aligned and live in the first 512M of memory.
*/
__vet_fdt:
+#ifdef CONFIG_ARM64_APPENDED_DTB
+ ldr x21, =_edata
+ add x21, x21, x28
+ ldr w0, [x21]
+#ifndef __AARCH64EB__
+ ldr w1, =0xedfe0dd0 // FDT magic word
+#else
+ ldr w1, =0xd00dfeed
+#endif
+ cmp w0, w1
+ b.ne 1f // no FDT found
+#endif
tst x21, #0x7
b.ne 1f
cmp x21, x24
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index a2c2986..c71bac3 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -54,6 +54,18 @@ PECOFF_FILE_ALIGNMENT = 0x200;
#define PECOFF_EDATA_PADDING
#endif
+/*
+ * Set FDT pointer 2MB aligned to ensure
+ * it don't cross a 2-megabyte boundary.
+ */
+FDT_FILE_ALIGNMENT = (1 << 21);
+#ifdef CONFIG_ARM64_APPENDED_DTB
+#define FDT_EDATA_PADDING \
+ .fdt_edata_padding : { BYTE(0); . = ALIGN(FDT_FILE_ALIGNMENT); }
+#else
+#define FDT_EDATA_PADDING
+#endif
+
#ifdef CONFIG_DEBUG_ALIGN_RODATA
#define ALIGN_DEBUG_RO . = ALIGN(1<<SECTION_SHIFT);
#define ALIGN_DEBUG_RO_MIN(min) ALIGN_DEBUG_RO
@@ -149,8 +161,13 @@ SECTIONS
_sdata = .;
RW_DATA_SECTION(64, PAGE_SIZE, THREAD_SIZE)
PECOFF_EDATA_PADDING
+ FDT_EDATA_PADDING /* 2MB aligned */
_edata = .;
+#ifdef CONFIG_ARM64_APPENDED_DTB
+ . += (1 << 21); /* maximum 2MB for FDT blob */
+#endif
+
BSS_SECTION(0, 0, 0)
. = ALIGN(PAGE_SIZE);
--
1.8.0
--
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