2016-10-15 8:29 GMT+02:00 Franck Jullien <franck.jullien@xxxxxxxxx>:
> 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
>
This patch result of a previous discussion [1] where the suggestion of
an appended DTB
would be better than the proposed empty builtin device tree.
Franck.
[1] http://comments.gmane.org/gmane.linux.drivers.devicetree/174636
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
