Re: [PATCH 1/4] of: Add support for linking device tree blobs into vmlinux

Michal Marek
2010-12-22T22:36:36Z

On 22.12.2010 20:57, dirk.brandewie@gmail.com wrote:
> From: Dirk Brandewie<dirk.brandewie@gmail.com>
>
> This patch adds support for linking device tree blob(s) into
> vmlinux. Modifies asm-generic/vmlinux.lds.h to add linking
> .dtb sections into vmlinux. To maintain compatiblity with the of/fdt
> driver code platforms MUST copy the blob to a non-init memory location
> before the kernel frees the .init.* sections in the image.
>
> Modifies scripts/Makefile.lib to add a kbuild command to
> compile DTS files to device tree blobs and a rule to create objects to
> wrap the blobs for linking.
>
> STRUCT_ALIGNMENT is defined in vmlinux.lds.h for use in the rule to
> create wrapper objects for the dtb in Makefile.lib. The
> STRUCT_ALIGN() macro in vmlinux.lds.h is modified to use the
> STRUCT_ALIGNMENT definition.
>
> The DTB's are placed on 32 byte boundries to allow parsing the blob
> with driver/of/fdt.c during early boot without having to copy the blob
> to get the structure alignment GCC expects.
>
> A DTB is linked in by adding the DTB object to the list of objects to
> be linked into vmlinux in the archtecture specific Makefile using
> obj-y += foo.dtb.o
>
> Signed-off-by: Dirk Brandewie<dirk.brandewie@gmail.com>

Hi,

you can add
Acked-by: Michal Marek <mmarek@suse.cz>
but I thing this series should go through the tip tree, as your primary
target seems to be x86 and patch 2/4 depends on the ce4100 code that is
only in tip.

Michal

> ---
> Documentation/kbuild/makefiles.txt | 15 +++++++++++++++
> include/asm-generic/vmlinux.lds.h | 13 +++++++++++--
> scripts/Makefile.lib | 23 +++++++++++++++++++++++
> 3 files changed, 49 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
> index 0ef00bd..86e3cd0 100644
> --- a/Documentation/kbuild/makefiles.txt
> +++ b/Documentation/kbuild/makefiles.txt
> @@ -1136,6 +1136,21 @@ When kbuild executes, the following steps are followed (roughly):
> resulting in the target file being recompiled for no
> obvious reason.
>
> + dtc
> + Create flattend device tree blob object suitable for linking
> + into vmlinux. Device tree blobs linked into vmlinux are placed
> + in an init section in the image. Platform code *must* copy the
> + blob to non-init memory prior to calling unflatten_device_tree().
> +
> + Example:
> + #arch/x86/platform/ce4100/Makefile
> + clean-files := *dtb.S
> +
> + DTC_FLAGS := -p 1024
> + obj-y += foo.dtb.o
> +
> + $(obj)/%.dtb: $(src)/%.dts
> + $(call cmd,dtc)
>
> --- 6.7 Custom kbuild commands
>
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index bd69d79..05cbad0 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -67,7 +67,8 @@
> * Align to a 32 byte boundary equal to the
> * alignment gcc 4.5 uses for a struct
> */
> -#define STRUCT_ALIGN() . = ALIGN(32)
> +#define STRUCT_ALIGNMENT 32
> +#define STRUCT_ALIGN() . = ALIGN(STRUCT_ALIGNMENT)
>
> /* The actual configuration determine if the init/exit sections
> * are handled as text/data or they can be discarded (which
> @@ -146,6 +147,13 @@
> #define TRACE_SYSCALLS()
> #endif
>
> +
> +#define KERNEL_DTB() \
> + STRUCT_ALIGN(); \
> + VMLINUX_SYMBOL(__dtb_start) = .; \
> + *(.dtb.init.rodata) \
> + VMLINUX_SYMBOL(__dtb_end) = .;
> +
> /* .data section */
> #define DATA_DATA \
> *(.data) \
> @@ -468,7 +476,8 @@
> MCOUNT_REC() \
> DEV_DISCARD(init.rodata) \
> CPU_DISCARD(init.rodata) \
> - MEM_DISCARD(init.rodata)
> + MEM_DISCARD(init.rodata) \
> + KERNEL_DTB()
>
> #define INIT_TEXT \
> *(.init.text) \
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index 4c72c11..7df8eb5 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -200,6 +200,29 @@ quiet_cmd_gzip = GZIP $@
> cmd_gzip = (cat $(filter-out FORCE,$^) | gzip -f -9> $@) || \
> (rm -f $@ ; false)
>
> +# DTC
> +# ---------------------------------------------------------------------------
> +
> +# Generate an assembly file to wrap the output of the device tree compiler
> +quiet_cmd_dt_S_dtb= DTB $@
> +cmd_dt_S_dtb= \
> +( \
> + echo '\#include<asm-generic/vmlinux.lds.h>'; \
> + echo '.section .dtb.init.rodata,"a"'; \
> + echo '.balign STRUCT_ALIGNMENT'; \
> + echo '.global __dtb_$(*F)_begin'; \
> + echo '__dtb_$(*F)_begin:'; \
> + echo '.incbin "$<" '; \
> + echo '__dtb_$(*F)_end:'; \
> + echo '.global __dtb_$(*F)_end'; \
> + echo '.balign STRUCT_ALIGNMENT'; \
> +)> $@
> +
> +$(obj)/%.dtb.S: $(obj)/%.dtb
> + $(call cmd,dt_S_dtb)
> +
> +quiet_cmd_dtc = DTC $@
> + cmd_dtc = $(objtree)/scripts/dtc/dtc -O dtb -o $@ -b 0 $(DTC_FLAGS) $<
>
> # Bzip2
> # ---------------------------------------------------------------------------