Commit aab94339 authored by Dirk Brandewie's avatar Dirk Brandewie Committed by Grant Likely
Browse files

of: Add support for linking device tree blobs into vmlinux 



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: default avatarDirk Brandewie <dirk.brandewie@gmail.com>
Acked-by: default avatarMichal Marek <mmarek@suse.cz>
[grant.likely@secretlab.ca: cleaned up whitespace inconsistencies]
Signed-off-by: default avatarGrant Likely <grant.likely@secretlab.ca>
parent cfb13c5d

Documentation/kbuild/makefiles.txt

+15 −0
Original line number Diff line number Diff line
@@ -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

include/asm-generic/vmlinux.lds.h

+11 −2
Original line number Diff line number Diff line
@@ -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)							\

scripts/Makefile.lib

+23 −0
Original line number Diff line number Diff line
@@ -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

# ---------------------------------------------------------------------------

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