1 # SPDX-License-Identifier: GPL-2.0+
2 # Copyright (c) 2016 Google, Inc
7 Firmware often consists of several components which must be packaged together.
8 For example, we may have SPL, U-Boot, a device tree and an environment area
9 grouped together and placed in MMC flash. When the system starts, it must be
10 able to find these pieces.
12 So far U-Boot has not provided a way to handle creating such images in a
13 general way. Each SoC does what it needs to build an image, often packing or
14 concatenating images in the U-Boot build system.
16 Binman aims to provide a mechanism for building images, from simple
17 SPL + U-Boot combinations, to more complex arrangements with many parts.
23 Binman reads your board's device tree and finds a node which describes the
24 required image layout. It uses this to work out what to place where. The
25 output file normally contains the device tree, so it is in principle possible
26 to read an image and extract its constituent parts.
32 So 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
34 place entries at a fixed location in the image, or fit them together with
35 suitable padding and alignment. It provides a way to process binaries before
36 they are included, by adding a Python plug-in. The device tree is available
37 to U-Boot at run-time so that the images can be interpreted.
39 Binman does not yet update the device tree with the final location of
40 everything when it is done. A simple C structure could be generated for
41 constrained environments like SPL (using dtoc) but this is also not
44 Binman can also support incorporating filesystems in the image if required.
45 For example x86 platforms may use CBFS in some cases.
47 Binman is intended for use with U-Boot but is designed to be general enough
48 to be useful in other image-packaging situations.
54 Packaging of firmware is quite a different task from building the various
55 parts. In many cases the various binaries which go into the image come from
56 separate build systems. For example, ARM Trusted Firmware is used on ARMv8
57 devices but is not built in the U-Boot tree. If a Linux kernel is included
58 in the firmware image, it is built elsewhere.
60 It is of course possible to add more and more build rules to the U-Boot
61 build system to cover these cases. It can shell out to other Makefiles and
62 build scripts. But it seems better to create a clear divide between building
63 software and packaging it.
65 At present this is handled by manual instructions, different for each board,
66 on how to create images that will boot. By turning these instructions into a
67 standard format, we can support making valid images for any board without
68 manual effort, lots of READMEs, etc.
71 - Each binary can have its own build system and tool chain without creating
72 any dependencies between them
73 - Avoids the need for a single-shot build: individual parts can be updated
74 and brought in as needed
75 - Provides for a standard image description available in the build and at
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,
80 SPL. It can be made available to other software also
81 - The image description is easily readable (it's a text file in device-tree
82 format) and permits flexible packing of binaries
88 Binman uses the following terms:
90 - image - an output file containing a firmware image
91 - binary - an input binary that goes into the image
97 FIT is U-Boot's official image format. It supports multiple binaries with
98 load / execution addresses, compression. It also supports verification
99 through hashing and RSA signatures.
101 FIT was originally designed to support booting a Linux kernel (with an
102 optional ramdisk) and device tree chosen from various options in the FIT.
103 Now that U-Boot supports configuration via device tree, it is possible to
104 load U-Boot from a FIT, with the device tree chosen by SPL.
106 Binman considers FIT to be one of the binaries it can place in the image.
108 Where possible it is best to put as much as possible in the FIT, with binman
109 used to deal with cases not covered by FIT. Examples include initial
110 execution (since FIT itself does not have an executable header) and dealing
111 with device boundaries, such as the read-only/read-write separation in SPI
114 For U-Boot, binman should not be used to create ad-hoc images in place of
118 Relationship to mkimage
119 -----------------------
121 The mkimage tool provides a means to create a FIT. Traditionally it has
122 needed an image description file: a device tree, like binman, but in a
123 different format. More recently it has started to support a '-f auto' mode
124 which can generate that automatically.
126 More relevant to binman, mkimage also permits creation of many SoC-specific
127 image types. These can be listed by running 'mkimage -T list'. Examples
128 include 'rksd', the Rockchip SD/MMC boot format. The mkimage tool is often
129 called from the U-Boot build system for this reason.
131 Binman considers the output files created by mkimage to be binary blobs
132 which it can place in an image. Binman does not replace the mkimage tool or
133 this purpose. It would be possible in some situtions to create a new entry
134 type for the images in mkimage, but this would not add functionality. It
135 seems better to use the mkiamge tool to generate binaries and avoid blurring
136 the boundaries between building input files (mkimage) and packaging then
137 into a final image (binman).
140 Example use of binman in U-Boot
141 -------------------------------
143 Binman aims to replace some of the ad-hoc image creation in the U-Boot
146 Consider sunxi. It has the following steps:
148 1. It uses a custom mksunxiboot tool to build an SPL image called
149 sunxi-spl.bin. This should probably move into mkimage.
151 2. It uses mkimage to package U-Boot into a legacy image file (so that it can
152 hold the load and execution address) called u-boot.img.
154 3. It builds a final output image called u-boot-sunxi-with-spl.bin which
155 consists of sunxi-spl.bin, some padding and u-boot.img.
157 Binman is intended to replace the last step. The U-Boot build system builds
158 u-boot.bin and sunxi-spl.bin. Binman can then take over creation of
159 sunxi-spl.bin (by calling mksunxiboot, or hopefully one day mkimage). In any
160 case, it would then create the image from the component parts.
162 This simplifies the U-Boot Makefile somewhat, since various pieces of logic
163 can be replaced by a call to binman.
166 Example use of binman for x86
167 -----------------------------
169 In most cases x86 images have a lot of binary blobs, 'black-box' code
170 provided by Intel which must be run for the platform to work. Typically
171 these blobs are not relocatable and must be placed at fixed areas in the
174 Currently this is handled by ifdtool, which places microcode, FSP, MRC, VGA
175 BIOS, reference code and Intel ME binaries into a u-boot.rom file.
177 Binman is intended to replace all of this, with ifdtool left to handle only
178 the configuration of the Intel-format descriptor.
186 binman -b <board_name>
188 to build an image for a board. The board name is the same name used when
189 configuring U-Boot (e.g. for sandbox_defconfig the board name is 'sandbox').
190 Binman assumes that the input files for the build are in ../b/<board_name>.
192 Or you can specify this explicitly:
194 binman -I <build_path>
196 where <build_path> is the build directory containing the output of the U-Boot
199 (Future work will make this more configurable)
201 In either case, binman picks up the device tree file (u-boot.dtb) and looks
202 for its instructions in the 'binman' node.
204 Binman has a few other options which you can see by running 'binman -h'.
207 Enabling binman for a board
208 ---------------------------
210 At present binman is invoked from a rule in the main Makefile. Typically you
211 will have a rule like:
213 ifneq ($(CONFIG_ARCH_<something>),)
214 u-boot-<your_suffix>.bin: <input_file_1> <input_file_2> checkbinman FORCE
215 $(call if_changed,binman)
218 This assumes that u-boot-<your_suffix>.bin is a target, and is the final file
219 that you need to produce. You can make it a target by adding it to ALL-y
220 either in the main Makefile or in a config.mk file in your arch subdirectory.
222 Once binman is executed it will pick up its instructions from a device-tree
223 file, typically <soc>-u-boot.dtsi, where <soc> is your CONFIG_SYS_SOC value.
224 You can use other, more specific CONFIG options - see 'Automatic .dtsi
228 Image description format
229 ------------------------
231 The binman node is called 'binman'. An example image description is shown
235 filename = "u-boot-sunxi-with-spl.bin";
238 filename = "spl/sunxi-spl.bin";
241 pos = <CONFIG_SPL_PAD_TO>;
246 This requests binman to create an image file called u-boot-sunxi-with-spl.bin
247 consisting of a specially formatted SPL (spl/sunxi-spl.bin, built by the
248 normal U-Boot Makefile), some 0xff padding, and a U-Boot legacy image. The
249 padding comes from the fact that the second binary is placed at
250 CONFIG_SPL_PAD_TO. If that line were omitted then the U-Boot binary would
251 immediately follow the SPL binary.
253 The binman node describes an image. The sub-nodes describe entries in the
254 image. Each entry represents a region within the overall image. The name of
255 the entry (blob, u-boot) tells binman what to put there. For 'blob' we must
256 provide a filename. For 'u-boot', binman knows that this means 'u-boot.bin'.
258 Entries are normally placed into the image sequentially, one after the other.
259 The image size is the total size of all entries. As you can see, you can
260 specify the start position of an entry using the 'pos' property.
262 Note that due to a device tree requirement, all entries must have a unique
263 name. If you want to put the same binary in the image multiple times, you can
264 use any unique name, with the 'type' property providing the type.
266 The attributes supported for entries are described below.
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.
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.
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
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.
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.
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.
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. If 'align-end' is not provided, no alignment is performed.
307 Note: This is not yet implemented in binman.
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.
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"'
320 The attributes supported for images are described below. Several are similar
321 to those for entries.
324 Sets the image size in bytes, for example 'size = <0x100000>' for a
328 This sets the alignment of the image size. For example, to ensure
329 that the image ends on a 512-byte boundary, use 'align-size = <512>'.
330 If 'align-size' is not provided, no alignment is performed.
333 This sets the padding before the image entries. The first entry will
334 be positionad after the padding. This defaults to 0.
337 This sets the padding after the image entries. The padding will be
338 placed after the last entry. This defaults to 0.
341 This specifies the pad byte to use when padding in the image. It
342 defaults to 0. To use 0xff, you would add 'pad-byte = <0xff>'.
345 This specifies the image filename. It defaults to 'image.bin'.
348 This causes binman to reorder the entries as needed to make sure they
349 are in increasing positional order. This can be used when your entry
350 order may not match the positional order. A common situation is where
351 the 'pos' properties are set by CONFIG options, so their ordering is
354 This is a boolean property so needs no value. To enable it, add a
355 line 'sort-by-pos;' to your description.
358 Normally only a single image is generated. To create more than one
359 image, put this property in the binman node. For example, this will
360 create image1.bin containing u-boot.bin, and image2.bin containing
361 both spl/u-boot-spl.bin and u-boot.bin:
379 For x86 machines the ROM positions start just before 4GB and extend
380 up so that the image finished at the 4GB boundary. This boolean
381 option can be enabled to support this. The image size must be
382 provided so that binman knows when the image should start. For an
383 8MB ROM, the position of the first entry would be 0xfff80000 with
384 this option, instead of 0 without this option.
387 Examples of the above options can be found in the tests. See the
388 tools/binman/test directory.
394 Some entries support special properties, documented here:
396 u-boot-with-ucode-ptr:
397 optional-ucode: boolean property to make microcode optional. If the
398 u-boot.bin image does not include microcode, no error will
402 Order of image creation
403 -----------------------
405 Image creation proceeds in the following order, for each entry in the image.
407 1. GetEntryContents() - the contents of each entry are obtained, normally by
408 reading from a file. This calls the Entry.ObtainContents() to read the
409 contents. The default version of Entry.ObtainContents() calls
410 Entry.GetDefaultFilename() and then reads that file. So a common mechanism
411 to select a file to read is to override that function in the subclass. The
412 functions must return True when they have read the contents. Binman will
413 retry calling the functions a few times if False is returned, allowing
414 dependencies between the contents of different entries.
416 2. GetEntryPositions() - calls Entry.GetPositions() for each entry. This can
417 return a dict containing entries that need updating. The key should be the
418 entry name and the value is a tuple (pos, size). This allows an entry to
419 provide the position and size for other entries. The default implementation
420 of GetEntryPositions() returns {}.
422 3. PackEntries() - calls Entry.Pack() which figures out the position and
423 size of an entry. The 'current' image position is passed in, and the function
424 returns the position immediately after the entry being packed. The default
425 implementation of Pack() is usually sufficient.
427 4. CheckSize() - checks that the contents of all the entries fits within
428 the image size. If the image does not have a defined size, the size is set
429 large enough to hold all the entries.
431 5. CheckEntries() - checks that the entries do not overlap, nor extend
434 6. ProcessEntryContents() - this calls Entry.ProcessContents() on each entry.
435 The default implementatoin does nothing. This can be overriden to adjust the
436 contents of an entry in some way. For example, it would be possible to create
437 an entry containing a hash of the contents of some other entries. At this
438 stage the position and size of entries should not be adjusted.
442 7. BuildImage() - builds the image and writes it to a file. This is the final
446 Automatic .dtsi inclusion
447 -------------------------
449 It is sometimes inconvenient to add a 'binman' node to the .dts file for each
450 board. This can be done by using #include to bring in a common file. Another
451 approach supported by the U-Boot build system is to automatically include
452 a common header. You can then put the binman node (and anything else that is
453 specific to U-Boot, such as u-boot,dm-pre-reloc properies) in that header
456 Binman will search for the following files in arch/<arch>/dts:
458 <dts>-u-boot.dtsi where <dts> is the base name of the .dts file
459 <CONFIG_SYS_SOC>-u-boot.dtsi
460 <CONFIG_SYS_CPU>-u-boot.dtsi
461 <CONFIG_SYS_VENDOR>-u-boot.dtsi
464 U-Boot will only use the first one that it finds. If you need to include a
465 more general file you can do that from the more specific file using #include.
466 If you are having trouble figuring out what is going on, you can uncomment
467 the 'warning' line in scripts/Makefile.lib to see what it has found:
469 # Uncomment for debugging
470 # This shows all the files that were considered and the one that we chose.
471 # u_boot_dtsi_options_debug = $(u_boot_dtsi_options_raw)
474 Access to binman entry positions at run time
475 --------------------------------------------
477 Binman assembles images and determines where each entry is placed in the image.
478 This information may be useful to U-Boot at run time. For example, in SPL it
479 is useful to be able to find the location of U-Boot so that it can be executed
480 when SPL is finished.
482 Binman allows you to declare symbols in the SPL image which are filled in
483 with their correct values during the build. For example:
485 binman_sym_declare(ulong, u_boot_any, pos);
487 declares a ulong value which will be assigned to the position of any U-Boot
488 image (u-boot.bin, u-boot.img, u-boot-nodtb.bin) that is present in the image.
489 You can access this value with something like:
491 ulong u_boot_pos = binman_sym(ulong, u_boot_any, pos);
493 Thus u_boot_pos will be set to the position of U-Boot in memory, assuming that
494 the whole image has been loaded, or is available in flash. You can then jump to
495 that address to start U-Boot.
497 At present this feature is only supported in SPL. In principle it is possible
498 to fill in such symbols in U-Boot proper, as well.
504 Binman is a critical tool and is designed to be very testable. Entry
505 implementations target 100% test coverage. Run 'binman -T' to check this.
507 To enable Python test coverage on Debian-type distributions (e.g. Ubuntu):
509 $ sudo apt-get install python-pip python-pytest
510 $ sudo pip install coverage
513 Advanced Features / Technical docs
514 ----------------------------------
516 The behaviour of entries is defined by the Entry class. All other entries are
517 a subclass of this. An important subclass is Entry_blob which takes binary
518 data from a file and places it in the entry. In fact most entry types are
519 subclasses of Entry_blob.
521 Each entry type is a separate file in the tools/binman/etype directory. Each
522 file contains a class called Entry_<type> where <type> is the entry type.
523 New entry types can be supported by adding new files in that directory.
524 These will automatically be detected by binman when needed.
526 Entry properties are documented in entry.py. The entry subclasses are free
527 to change the values of properties to support special behaviour. For example,
528 when Entry_blob loads a file, it sets content_size to the size of the file.
529 Entry classes can adjust other entries. For example, an entry that knows
530 where other entries should be positioned can set up those entries' positions
531 so they don't need to be set in the binman decription. It can also adjust
534 Most of the time such essoteric behaviour is not needed, but it can be
535 essential for complex images.
537 If you need to specify a particular device-tree compiler to use, you can define
538 the DTC environment variable. This can be useful when the system dtc is too
545 Binman takes a lot of inspiration from a Chrome OS tool called
546 'cros_bundle_firmware', which I wrote some years ago. That tool was based on
547 a reasonably simple and sound design but has expanded greatly over the
548 years. In particular its handling of x86 images is convoluted.
550 Quite a few lessons have been learned which are hopefully be applied here.
556 On the face of it, a tool to create firmware images should be fairly simple:
557 just find all the input binaries and place them at the right place in the
558 image. The difficulty comes from the wide variety of input types (simple
559 flat binaries containing code, packaged data with various headers), packing
560 requirments (alignment, spacing, device boundaries) and other required
561 features such as hierarchical images.
563 The design challenge is to make it easy to create simple images, while
564 allowing the more complex cases to be supported. For example, for most
565 images we don't much care exactly where each binary ends up, so we should
566 not have to specify that unnecessarily.
568 New entry types should aim to provide simple usage where possible. If new
569 core features are needed, they can be added in the Entry base class.
576 - Fill out the device tree to include the final position and size of each
577 entry (since the input file may not always specify these). See also
578 'Access to binman entry positions at run time' above
579 - Use of-platdata to make the information available to code that is unable
580 to use device tree (such as a very small SPL image)
581 - Write an image map to a text file
582 - Allow easy building of images by specifying just the board name
583 - Produce a full Python binding for libfdt (for upstream)
584 - Add an option to decode an image into the constituent binaries
585 - Suppoort hierarchical images (packing of binaries into another binary
586 which is then placed in the image)
587 - Support building an image for a board (-b) more completely, with a
588 configurable build directory
589 - Consider making binman work with buildman, although if it is used in the
590 Makefile, this will be automatic
591 - Implement align-end
594 Simon Glass <sjg@chromium.org>