This patch provides the ability to boot using a device tree that is appended
to the raw binary bzImage (e.g. cat bzImage <filename>.dtb > bzImage_w_dtb).
Based on Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx> work on x86
builtin dtb support.
Signed-off-by: Franck Jullien <franck.jullien@xxxxxxxxx>
---
arch/x86/Kconfig | 19 ++++++++++++
arch/x86/boot/compressed/head_32.S | 61 ++++++++++++++++++++++++++++++++++++++
arch/x86/boot/compressed/head_64.S | 53 +++++++++++++++++++++++++++++++++
arch/x86/boot/compressed/misc.c | 40 +++++++++++++++++++++++++
4 files changed, 173 insertions(+)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index bada636..722d846 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2222,6 +2222,25 @@ config MODIFY_LDT_SYSCALL
Saying 'N' here may make sense for embedded or server kernels.
+config X86_APPENDED_DTB
+ bool "Use appended device tree blob to bzImage"
+ depends on OF
+ select OF_EARLY_FLATTREE
+ help
+ With this option, the boot code will look for a device tree binary
+ (DTB) appended to bzImage
+ (e.g. cat bzImage <filename>.dtb > bzImage_w_dtb).
+
+ This is meant as a backward compatibility convenience for those
+ systems with a bootloader that can't be upgraded to accommodate
+ the documented boot protocol using a device tree.
+
+ Beware that there is very little in terms of protection against
+ this option being confused by leftover garbage in memory that might
+ look like a DTB header after a reboot if no actual DTB is appended
+ to bzImage. Do not leave this option active in a production kernel
+ if you don't intend to always append a DTB.
+
source "kernel/livepatch/Kconfig"
endmenu
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index fd0b6a2..e28a586 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -201,6 +201,40 @@ preferred_addr:
cld
popl %esi
+#if CONFIG_X86_APPENDED_DTB
+/*
+ * Check if an appended device tree blob is present.
+ */
+
+ movl $0, dtb_sz(%ebp)
+
+ movl $(_edata - startup_32), %ecx
+ leal startup_32(%ebp), %edx
+
+ /* Calculate the appended DTB address. We need to add 4 bytes for
+ * CRC and padding to the next 16-byte paragraph (see ../tools/build.c)
+ */
+ addl $19, %ecx
+ andl $0xfffffff0, %ecx
+ addl %edx, %ecx
+
+ movl (%ecx), %eax
+
+ /* DTB sig is 0xd00dfeed big endian */
+ movl $0xedfe0dd0, %edx
+
+ cmpl %eax, %edx
+ jne 2f
+
+ /* Get DTB size */
+ movl 4(%ecx), %edx
+ bswap %edx
+
+ movl %edx, dtb_sz(%ebp)
+ movl %ecx, dtb_address(%ebp)
+2:
+#endif
+
/*
* Jump to the relocated address.
*/
@@ -234,6 +268,7 @@ relocated:
jmp 1b
2:
+ pushl %ebp
/*
* Do the extraction, and jump to the new kernel..
*/
@@ -255,12 +290,38 @@ relocated:
call extract_kernel /* returns kernel location in %eax */
addl $24, %esp
+
+ popl %ebp
+
+#if CONFIG_X86_APPENDED_DTB
+ pushl %eax
+
+ movl dtb_sz(%ebp), %edi /* dtb size */
+ cmpl $0, %edi
+ je 1f
+ movl dtb_address(%ebp), %eax /* dtb start */
+
+ pushl %edi /* dtb_size */
+ pushl %eax /* dtb_start */
+ pushl %esi /* real mode pointer */
+ call relocate_dtb
+ addl $12,%esp
+1:
+ popl %eax
+#endif
+
/*
* Jump to the extracted kernel.
*/
xorl %ebx, %ebx
jmp *%eax
+ .data
+dtb_address:
+ .long 0
+dtb_sz:
+ .long 0
+
#ifdef CONFIG_EFI_STUB
.data
efi32_config:
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index efdfba2..3ad2086 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -365,6 +365,45 @@ preferred_addr:
cld
popq %rsi
+#ifdef CONFIG_X86_APPENDED_DTB
+/*
+ * Check if an appended device tree blob is present.
+ * r13 = appended dtb size (0 if not present)
+ * r12 = address of the appended dtb
+ */
+ pushq %rax
+ pushq %rdx
+
+ xorq %r13, %r13
+
+ movq $(_edata - startup_32), %rcx
+ leaq startup_32(%rip), %rdx
+
+ /* Calculate the appended DTB address. We need to add 4 bytes for
+ * CRC and padding to the next 16-byte paragraph (see ../tools/build.c)
+ */
+ addq $19, %rcx
+ andq $0xfffffffffffffff0, %rcx
+ addq %rdx, %rcx
+ movq %rcx, %r12
+
+ movq (%rcx), %rax
+
+ /* DTB sig is 0xd00dfeed big endian */
+ movl $0xedfe0dd0, %edx
+
+ cmpl %eax, %edx
+ jne 1f
+
+ /* Get DTB size */
+ movl 4(%rcx), %edx
+ bswap %edx
+ movq %rdx, %r13
+1:
+ popq %rdx
+ popq %rax
+#endif
+
/*
* Jump to the relocated address.
*/
@@ -424,6 +463,20 @@ relocated:
call extract_kernel /* returns kernel location in %rax */
popq %rsi
+#ifdef CONFIG_X86_APPENDED_DTB
+ cmpq $0,%r13
+ je 2f
+ pushq %rsi
+ pushq %rax /* save address */
+ movq %rsi, %rdi /* real mode address */
+ movq %r12, %rsi /* dtb start */
+ movq %r13, %rdx /* dtb size */
+ call relocate_dtb
+ popq %rax
+ popq %rsi
+2:
+#endif
+
/*
* Jump to the decompressed kernel.
*/
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index b3c5a5f0..1b66a74 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -409,3 +409,43 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
debug_putstr("done.\nBooting the kernel.\n");
return output;
}
+
+#ifdef CONFIG_X86_APPENDED_DTB
+asmlinkage __visible void relocate_dtb(void *rmode,
+ unsigned char *dtb_data,
+ unsigned long dtb_size)
+{
+
+ struct boot_params *boot_params = rmode;
+ struct setup_data *data;
+ u32 pa_data, pa_next;
+ u32 data_len, data_type;
+
+ /* first iterate over the setup data to find a DTB if it exists */
+ pa_data = boot_params->hdr.setup_data;
+ while (pa_data) {
+ data = (void *)(unsigned long)pa_data;
+ data_len = data->len + sizeof(struct setup_data);
+ data_type = data->type;
+ pa_next = data->next;
+
+ if (data_type == SETUP_DTB) {
+ debug_putstr("Using bootloader DTB\n");
+ return;
+ }
+
+ pa_data = pa_next;
+ }
+
+ /* insert the DTB in the beginning */
+ data = malloc(sizeof(*data) + dtb_size);
+ data->type = SETUP_DTB;
+ data->next = boot_params->hdr.setup_data;
+ data->len = dtb_size;
+ memcpy(&data->data[0], dtb_data, dtb_size);
+ boot_params->hdr.setup_data = (uintptr_t)data;
+
+ debug_putstr("Using appended DTB\n");
+
+}
+#endif
--
2.7.4
--
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