xref: /openbmc/u-boot/tools/binman/README (revision bbbb50f9)
1# SPDX-License-Identifier: GPL-2.0+
2# Copyright (c) 2016 Google, Inc
3
4Introduction
5------------
6
7Firmware often consists of several components which must be packaged together.
8For example, we may have SPL, U-Boot, a device tree and an environment area
9grouped together and placed in MMC flash. When the system starts, it must be
10able to find these pieces.
11
12So far U-Boot has not provided a way to handle creating such images in a
13general way. Each SoC does what it needs to build an image, often packing or
14concatenating images in the U-Boot build system.
15
16Binman aims to provide a mechanism for building images, from simple
17SPL + U-Boot combinations, to more complex arrangements with many parts.
18
19
20What it does
21------------
22
23Binman reads your board's device tree and finds a node which describes the
24required image layout. It uses this to work out what to place where. The
25output file normally contains the device tree, so it is in principle possible
26to read an image and extract its constituent parts.
27
28
29Features
30--------
31
32So far binman is pretty simple. It supports binary blobs, such as 'u-boot',
33'spl' and 'fdt'. It supports empty entries (such as setting to 0xff). It can
34place entries at a fixed location in the image, or fit them together with
35suitable padding and alignment. It provides a way to process binaries before
36they are included, by adding a Python plug-in. The device tree is available
37to U-Boot at run-time so that the images can be interpreted.
38
39Binman does not yet update the device tree with the final location of
40everything when it is done. A simple C structure could be generated for
41constrained environments like SPL (using dtoc) but this is also not
42implemented.
43
44Binman can also support incorporating filesystems in the image if required.
45For example x86 platforms may use CBFS in some cases.
46
47Binman is intended for use with U-Boot but is designed to be general enough
48to be useful in other image-packaging situations.
49
50
51Motivation
52----------
53
54Packaging of firmware is quite a different task from building the various
55parts. In many cases the various binaries which go into the image come from
56separate build systems. For example, ARM Trusted Firmware is used on ARMv8
57devices but is not built in the U-Boot tree. If a Linux kernel is included
58in the firmware image, it is built elsewhere.
59
60It is of course possible to add more and more build rules to the U-Boot
61build system to cover these cases. It can shell out to other Makefiles and
62build scripts. But it seems better to create a clear divide between building
63software and packaging it.
64
65At present this is handled by manual instructions, different for each board,
66on how to create images that will boot. By turning these instructions into a
67standard format, we can support making valid images for any board without
68manual effort, lots of READMEs, etc.
69
70Benefits:
71- Each binary can have its own build system and tool chain without creating
72any dependencies between them
73- Avoids the need for a single-shot build: individual parts can be updated
74and brought in as needed
75- Provides for a standard image description available in the build and at
76run-time
77- SoC-specific image-signing tools can be accomodated
78- Avoids cluttering the U-Boot build system with image-building code
79- The image description is automatically available at run-time in U-Boot,
80SPL. It can be made available to other software also
81- The image description is easily readable (it's a text file in device-tree
82format) and permits flexible packing of binaries
83
84
85Terminology
86-----------
87
88Binman uses the following terms:
89
90- image - an output file containing a firmware image
91- binary - an input binary that goes into the image
92
93
94Relationship to FIT
95-------------------
96
97FIT is U-Boot's official image format. It supports multiple binaries with
98load / execution addresses, compression. It also supports verification
99through hashing and RSA signatures.
100
101FIT was originally designed to support booting a Linux kernel (with an
102optional ramdisk) and device tree chosen from various options in the FIT.
103Now that U-Boot supports configuration via device tree, it is possible to
104load U-Boot from a FIT, with the device tree chosen by SPL.
105
106Binman considers FIT to be one of the binaries it can place in the image.
107
108Where possible it is best to put as much as possible in the FIT, with binman
109used to deal with cases not covered by FIT. Examples include initial
110execution (since FIT itself does not have an executable header) and dealing
111with device boundaries, such as the read-only/read-write separation in SPI
112flash.
113
114For U-Boot, binman should not be used to create ad-hoc images in place of
115FIT.
116
117
118Relationship to mkimage
119-----------------------
120
121The mkimage tool provides a means to create a FIT. Traditionally it has
122needed an image description file: a device tree, like binman, but in a
123different format. More recently it has started to support a '-f auto' mode
124which can generate that automatically.
125
126More relevant to binman, mkimage also permits creation of many SoC-specific
127image types. These can be listed by running 'mkimage -T list'. Examples
128include 'rksd', the Rockchip SD/MMC boot format. The mkimage tool is often
129called from the U-Boot build system for this reason.
130
131Binman considers the output files created by mkimage to be binary blobs
132which it can place in an image. Binman does not replace the mkimage tool or
133this purpose. It would be possible in some situtions to create a new entry
134type for the images in mkimage, but this would not add functionality. It
135seems better to use the mkiamge tool to generate binaries and avoid blurring
136the boundaries between building input files (mkimage) and packaging then
137into a final image (binman).
138
139
140Example use of binman in U-Boot
141-------------------------------
142
143Binman aims to replace some of the ad-hoc image creation in the U-Boot
144build system.
145
146Consider sunxi. It has the following steps:
147
1481. It uses a custom mksunxiboot tool to build an SPL image called
149sunxi-spl.bin. This should probably move into mkimage.
150
1512. It uses mkimage to package U-Boot into a legacy image file (so that it can
152hold the load and execution address) called u-boot.img.
153
1543. It builds a final output image called u-boot-sunxi-with-spl.bin which
155consists of sunxi-spl.bin, some padding and u-boot.img.
156
157Binman is intended to replace the last step. The U-Boot build system builds
158u-boot.bin and sunxi-spl.bin. Binman can then take over creation of
159sunxi-spl.bin (by calling mksunxiboot, or hopefully one day mkimage). In any
160case, it would then create the image from the component parts.
161
162This simplifies the U-Boot Makefile somewhat, since various pieces of logic
163can be replaced by a call to binman.
164
165
166Example use of binman for x86
167-----------------------------
168
169In most cases x86 images have a lot of binary blobs, 'black-box' code
170provided by Intel which must be run for the platform to work. Typically
171these blobs are not relocatable and must be placed at fixed areas in the
172firmare image.
173
174Currently this is handled by ifdtool, which places microcode, FSP, MRC, VGA
175BIOS, reference code and Intel ME binaries into a u-boot.rom file.
176
177Binman is intended to replace all of this, with ifdtool left to handle only
178the configuration of the Intel-format descriptor.
179
180
181Running binman
182--------------
183
184Type:
185
186	binman -b <board_name>
187
188to build an image for a board. The board name is the same name used when
189configuring U-Boot (e.g. for sandbox_defconfig the board name is 'sandbox').
190Binman assumes that the input files for the build are in ../b/<board_name>.
191
192Or you can specify this explicitly:
193
194	binman -I <build_path>
195
196where <build_path> is the build directory containing the output of the U-Boot
197build.
198
199(Future work will make this more configurable)
200
201In either case, binman picks up the device tree file (u-boot.dtb) and looks
202for its instructions in the 'binman' node.
203
204Binman has a few other options which you can see by running 'binman -h'.
205
206
207Enabling binman for a board
208---------------------------
209
210At present binman is invoked from a rule in the main Makefile. Typically you
211will have a rule like:
212
213ifneq ($(CONFIG_ARCH_<something>),)
214u-boot-<your_suffix>.bin: <input_file_1> <input_file_2> checkbinman FORCE
215	$(call if_changed,binman)
216endif
217
218This assumes that u-boot-<your_suffix>.bin is a target, and is the final file
219that you need to produce. You can make it a target by adding it to ALL-y
220either in the main Makefile or in a config.mk file in your arch subdirectory.
221
222Once binman is executed it will pick up its instructions from a device-tree
223file, typically <soc>-u-boot.dtsi, where <soc> is your CONFIG_SYS_SOC value.
224You can use other, more specific CONFIG options - see 'Automatic .dtsi
225inclusion' below.
226
227
228Image description format
229------------------------
230
231The binman node is called 'binman'. An example image description is shown
232below:
233
234	binman {
235		filename = "u-boot-sunxi-with-spl.bin";
236		pad-byte = <0xff>;
237		blob {
238			filename = "spl/sunxi-spl.bin";
239		};
240		u-boot {
241			pos = <CONFIG_SPL_PAD_TO>;
242		};
243	};
244
245
246This requests binman to create an image file called u-boot-sunxi-with-spl.bin
247consisting of a specially formatted SPL (spl/sunxi-spl.bin, built by the
248normal U-Boot Makefile), some 0xff padding, and a U-Boot legacy image. The
249padding comes from the fact that the second binary is placed at
250CONFIG_SPL_PAD_TO. If that line were omitted then the U-Boot binary would
251immediately follow the SPL binary.
252
253The binman node describes an image. The sub-nodes describe entries in the
254image. Each entry represents a region within the overall image. The name of
255the entry (blob, u-boot) tells binman what to put there. For 'blob' we must
256provide a filename. For 'u-boot', binman knows that this means 'u-boot.bin'.
257
258Entries are normally placed into the image sequentially, one after the other.
259The image size is the total size of all entries. As you can see, you can
260specify the start position of an entry using the 'pos' property.
261
262Note that due to a device tree requirement, all entries must have a unique
263name. If you want to put the same binary in the image multiple times, you can
264use any unique name, with the 'type' property providing the type.
265
266The attributes supported for entries are described below.
267
268pos:
269	This sets the position of an entry within the image. The first byte
270	of the image is normally at position 0. If 'pos' is not provided,
271	binman sets it to the end of the previous region, or the start of
272	the image's entry area (normally 0) if there is no previous region.
273
274align:
275	This sets the alignment of the entry. The entry position is adjusted
276	so that the entry starts on an aligned boundary within the image. For
277	example 'align = <16>' means that the entry will start on a 16-byte
278	boundary. Alignment shold be a power of 2. If 'align' is not
279	provided, no alignment is performed.
280
281size:
282	This sets the size of the entry. The contents will be padded out to
283	this size. If this is not provided, it will be set to the size of the
284	contents.
285
286pad-before:
287	Padding before the contents of the entry. Normally this is 0, meaning
288	that the contents start at the beginning of the entry. This can be
289	offset the entry contents a little. Defaults to 0.
290
291pad-after:
292	Padding after the contents of the entry. Normally this is 0, meaning
293	that the entry ends at the last byte of content (unless adjusted by
294	other properties). This allows room to be created in the image for
295	this entry to expand later. Defaults to 0.
296
297align-size:
298	This sets the alignment of the entry size. For example, to ensure
299	that the size of an entry is a multiple of 64 bytes, set this to 64.
300	If 'align-size' is not provided, no alignment is performed.
301
302align-end:
303	This sets the alignment of the end of an entry. Some entries require
304	that they end on an alignment boundary, regardless of where they
305	start. This does not move the start of the entry, so the contents of
306	the entry will still start at the beginning. But there may be padding
307	at the end. If 'align-end' is not provided, no alignment is performed.
308
309filename:
310	For 'blob' types this provides the filename containing the binary to
311	put into the entry. If binman knows about the entry type (like
312	u-boot-bin), then there is no need to specify this.
313
314type:
315	Sets the type of an entry. This defaults to the entry name, but it is
316	possible to use any name, and then add (for example) 'type = "u-boot"'
317	to specify the type.
318
319pos-unset:
320	Indicates that the position of this entry should not be set by placing
321	it immediately after the entry before. Instead, is set by another
322	entry which knows where this entry should go. When this boolean
323	property is present, binman will give an error if another entry does
324	not set the position (with the GetPositions() method).
325
326
327The attributes supported for images are described below. Several are similar
328to those for entries.
329
330size:
331	Sets the image size in bytes, for example 'size = <0x100000>' for a
332	1MB image.
333
334align-size:
335	This sets the alignment of the image size. For example, to ensure
336	that the image ends on a 512-byte boundary, use 'align-size = <512>'.
337	If 'align-size' is not provided, no alignment is performed.
338
339pad-before:
340	This sets the padding before the image entries. The first entry will
341	be positionad after the padding. This defaults to 0.
342
343pad-after:
344	This sets the padding after the image entries. The padding will be
345	placed after the last entry. This defaults to 0.
346
347pad-byte:
348	This specifies the pad byte to use when padding in the image. It
349	defaults to 0. To use 0xff, you would add 'pad-byte = <0xff>'.
350
351filename:
352	This specifies the image filename. It defaults to 'image.bin'.
353
354sort-by-pos:
355	This causes binman to reorder the entries as needed to make sure they
356	are in increasing positional order. This can be used when your entry
357	order may not match the positional order. A common situation is where
358	the 'pos' properties are set by CONFIG options, so their ordering is
359	not known a priori.
360
361	This is a boolean property so needs no value. To enable it, add a
362	line 'sort-by-pos;' to your description.
363
364multiple-images:
365	Normally only a single image is generated. To create more than one
366	image, put this property in the binman node. For example, this will
367	create image1.bin containing u-boot.bin, and image2.bin containing
368	both spl/u-boot-spl.bin and u-boot.bin:
369
370	binman {
371		multiple-images;
372		image1 {
373			u-boot {
374			};
375		};
376
377		image2 {
378			spl {
379			};
380			u-boot {
381			};
382		};
383	};
384
385end-at-4gb:
386	For x86 machines the ROM positions start just before 4GB and extend
387	up so that the image finished at the 4GB boundary. This boolean
388	option can be enabled to support this. The image size must be
389	provided so that binman knows when the image should start. For an
390	8MB ROM, the position of the first entry would be 0xfff80000 with
391	this option, instead of 0 without this option.
392
393
394Examples of the above options can be found in the tests. See the
395tools/binman/test directory.
396
397It is possible to have the same binary appear multiple times in the image,
398either by using a unit number suffix (u-boot@0, u-boot@1) or by using a
399different name for each and specifying the type with the 'type' attribute.
400
401
402Sections and hiearchical images
403-------------------------------
404
405Sometimes it is convenient to split an image into several pieces, each of which
406contains its own set of binaries. An example is a flash device where part of
407the image is read-only and part is read-write. We can set up sections for each
408of these, and place binaries in them independently. The image is still produced
409as a single output file.
410
411This feature provides a way of creating hierarchical images. For example here
412is an example image with two copies of U-Boot. One is read-only (ro), intended
413to be written only in the factory. Another is read-write (rw), so that it can be
414upgraded in the field. The sizes are fixed so that the ro/rw boundary is known
415and can be programmed:
416
417	binman {
418		section@0 {
419			read-only;
420			name-prefix = "ro-";
421			size = <0x100000>;
422			u-boot {
423			};
424		};
425		section@1 {
426			name-prefix = "rw-";
427			size = <0x100000>;
428			u-boot {
429			};
430		};
431	};
432
433This image could be placed into a SPI flash chip, with the protection boundary
434set at 1MB.
435
436A few special properties are provided for sections:
437
438read-only:
439	Indicates that this section is read-only. This has no impact on binman's
440	operation, but his property can be read at run time.
441
442name-prefix:
443	This string is prepended to all the names of the binaries in the
444	section. In the example above, the 'u-boot' binaries which actually be
445	renamed to 'ro-u-boot' and 'rw-u-boot'. This can be useful to
446	distinguish binaries with otherwise identical names.
447
448
449Special properties
450------------------
451
452Some entries support special properties, documented here:
453
454u-boot-with-ucode-ptr:
455	optional-ucode: boolean property to make microcode optional. If the
456		u-boot.bin image does not include microcode, no error will
457		be generated.
458
459
460Order of image creation
461-----------------------
462
463Image creation proceeds in the following order, for each entry in the image.
464
4651. AddMissingProperties() - binman can add calculated values to the device
466tree as part of its processing, for example the position and size of each
467entry. This method adds any properties associated with this, expanding the
468device tree as needed. These properties can have placeholder values which are
469set later by SetCalculatedProperties(). By that stage the size of sections
470cannot be changed (since it would cause the images to need to be repacked),
471but the correct values can be inserted.
472
4732. ProcessFdt() - process the device tree information as required by the
474particular entry. This may involve adding or deleting properties. If the
475processing is complete, this method should return True. If the processing
476cannot complete because it needs the ProcessFdt() method of another entry to
477run first, this method should return False, in which case it will be called
478again later.
479
4803. GetEntryContents() - the contents of each entry are obtained, normally by
481reading from a file. This calls the Entry.ObtainContents() to read the
482contents. The default version of Entry.ObtainContents() calls
483Entry.GetDefaultFilename() and then reads that file. So a common mechanism
484to select a file to read is to override that function in the subclass. The
485functions must return True when they have read the contents. Binman will
486retry calling the functions a few times if False is returned, allowing
487dependencies between the contents of different entries.
488
4894. GetEntryPositions() - calls Entry.GetPositions() for each entry. This can
490return a dict containing entries that need updating. The key should be the
491entry name and the value is a tuple (pos, size). This allows an entry to
492provide the position and size for other entries. The default implementation
493of GetEntryPositions() returns {}.
494
4955. PackEntries() - calls Entry.Pack() which figures out the position and
496size of an entry. The 'current' image position is passed in, and the function
497returns the position immediately after the entry being packed. The default
498implementation of Pack() is usually sufficient.
499
5006. CheckSize() - checks that the contents of all the entries fits within
501the image size. If the image does not have a defined size, the size is set
502large enough to hold all the entries.
503
5047. CheckEntries() - checks that the entries do not overlap, nor extend
505outside the image.
506
5078. SetCalculatedProperties() - update any calculated properties in the device
508tree. This sets the correct 'pos' and 'size' vaues, for example.
509
5109. ProcessEntryContents() - this calls Entry.ProcessContents() on each entry.
511The default implementatoin does nothing. This can be overriden to adjust the
512contents of an entry in some way. For example, it would be possible to create
513an entry containing a hash of the contents of some other entries. At this
514stage the position and size of entries should not be adjusted.
515
51610. WriteSymbols() - write the value of symbols into the U-Boot SPL binary.
517See 'Access to binman entry positions at run time' below for a description of
518what happens in this stage.
519
52011. BuildImage() - builds the image and writes it to a file. This is the final
521step.
522
523
524Automatic .dtsi inclusion
525-------------------------
526
527It is sometimes inconvenient to add a 'binman' node to the .dts file for each
528board. This can be done by using #include to bring in a common file. Another
529approach supported by the U-Boot build system is to automatically include
530a common header. You can then put the binman node (and anything else that is
531specific to U-Boot, such as u-boot,dm-pre-reloc properies) in that header
532file.
533
534Binman will search for the following files in arch/<arch>/dts:
535
536   <dts>-u-boot.dtsi where <dts> is the base name of the .dts file
537   <CONFIG_SYS_SOC>-u-boot.dtsi
538   <CONFIG_SYS_CPU>-u-boot.dtsi
539   <CONFIG_SYS_VENDOR>-u-boot.dtsi
540   u-boot.dtsi
541
542U-Boot will only use the first one that it finds. If you need to include a
543more general file you can do that from the more specific file using #include.
544If you are having trouble figuring out what is going on, you can uncomment
545the 'warning' line in scripts/Makefile.lib to see what it has found:
546
547   # Uncomment for debugging
548   # This shows all the files that were considered and the one that we chose.
549   # u_boot_dtsi_options_debug = $(u_boot_dtsi_options_raw)
550
551
552Access to binman entry positions at run time
553--------------------------------------------
554
555Binman assembles images and determines where each entry is placed in the image.
556This information may be useful to U-Boot at run time. For example, in SPL it
557is useful to be able to find the location of U-Boot so that it can be executed
558when SPL is finished.
559
560Binman allows you to declare symbols in the SPL image which are filled in
561with their correct values during the build. For example:
562
563    binman_sym_declare(ulong, u_boot_any, pos);
564
565declares a ulong value which will be assigned to the position of any U-Boot
566image (u-boot.bin, u-boot.img, u-boot-nodtb.bin) that is present in the image.
567You can access this value with something like:
568
569    ulong u_boot_pos = binman_sym(ulong, u_boot_any, pos);
570
571Thus u_boot_pos will be set to the position of U-Boot in memory, assuming that
572the whole image has been loaded, or is available in flash. You can then jump to
573that address to start U-Boot.
574
575At present this feature is only supported in SPL. In principle it is possible
576to fill in such symbols in U-Boot proper, as well.
577
578
579Map files
580---------
581
582The -m option causes binman to output a .map file for each image that it
583generates. This shows the position and size of each entry. For example:
584
585    Position      Size  Name
586    00000000  00000010  section@0
587     00000000  00000004  u-boot
588    00000010  00000010  section@1
589     00000000  00000004  u-boot
590
591This shows a hierarchical image with two sections, each with a single entry. The
592positions of the sections are absolute hex byte offsets within the image. The
593positions of the entries are relative to their respective sections. The size of
594each entry is also shown, in bytes (hex). The indentation shows the entries
595nested inside their sections.
596
597
598Code coverage
599-------------
600
601Binman is a critical tool and is designed to be very testable. Entry
602implementations target 100% test coverage. Run 'binman -T' to check this.
603
604To enable Python test coverage on Debian-type distributions (e.g. Ubuntu):
605
606   $ sudo apt-get install python-coverage python-pytest
607
608
609Advanced Features / Technical docs
610----------------------------------
611
612The behaviour of entries is defined by the Entry class. All other entries are
613a subclass of this. An important subclass is Entry_blob which takes binary
614data from a file and places it in the entry. In fact most entry types are
615subclasses of Entry_blob.
616
617Each entry type is a separate file in the tools/binman/etype directory. Each
618file contains a class called Entry_<type> where <type> is the entry type.
619New entry types can be supported by adding new files in that directory.
620These will automatically be detected by binman when needed.
621
622Entry properties are documented in entry.py. The entry subclasses are free
623to change the values of properties to support special behaviour. For example,
624when Entry_blob loads a file, it sets content_size to the size of the file.
625Entry classes can adjust other entries. For example, an entry that knows
626where other entries should be positioned can set up those entries' positions
627so they don't need to be set in the binman decription. It can also adjust
628entry contents.
629
630Most of the time such essoteric behaviour is not needed, but it can be
631essential for complex images.
632
633If you need to specify a particular device-tree compiler to use, you can define
634the DTC environment variable. This can be useful when the system dtc is too
635old.
636
637
638History / Credits
639-----------------
640
641Binman takes a lot of inspiration from a Chrome OS tool called
642'cros_bundle_firmware', which I wrote some years ago. That tool was based on
643a reasonably simple and sound design but has expanded greatly over the
644years. In particular its handling of x86 images is convoluted.
645
646Quite a few lessons have been learned which are hopefully applied here.
647
648
649Design notes
650------------
651
652On the face of it, a tool to create firmware images should be fairly simple:
653just find all the input binaries and place them at the right place in the
654image. The difficulty comes from the wide variety of input types (simple
655flat binaries containing code, packaged data with various headers), packing
656requirments (alignment, spacing, device boundaries) and other required
657features such as hierarchical images.
658
659The design challenge is to make it easy to create simple images, while
660allowing the more complex cases to be supported. For example, for most
661images we don't much care exactly where each binary ends up, so we should
662not have to specify that unnecessarily.
663
664New entry types should aim to provide simple usage where possible. If new
665core features are needed, they can be added in the Entry base class.
666
667
668To do
669-----
670
671Some ideas:
672- Use of-platdata to make the information available to code that is unable
673  to use device tree (such as a very small SPL image)
674- Allow easy building of images by specifying just the board name
675- Produce a full Python binding for libfdt (for upstream). This is nearing
676    completion but some work remains
677- Add an option to decode an image into the constituent binaries
678- Support building an image for a board (-b) more completely, with a
679  configurable build directory
680- Consider making binman work with buildman, although if it is used in the
681  Makefile, this will be automatic
682
683--
684Simon Glass <sjg@chromium.org>
6857/7/2016
686