binman: Introduce binman, a tool for building binary images
This adds the basic code for binman, including command parsing, processing
of entries and generation of images.
So far no entry types are supported. These will be added in future commits
as examples of how to add new types.
See the README for documentation.
Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/tools/binman/README b/tools/binman/README
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+# Copyright (c) 2016 Google, Inc
+#
+# SPDX-License-Identifier: GPL-2.0+
+#
+
+Introduction
+------------
+
+Firmware often consists of several components which must be packaged together.
+For example, we may have SPL, U-Boot, a device tree and an environment area
+grouped together and placed in MMC flash. When the system starts, it must be
+able to find these pieces.
+
+So far U-Boot has not provided a way to handle creating such images in a
+general way. Each SoC does what it needs to build an image, often packing or
+concatenating images in the U-Boot build system.
+
+Binman aims to provide a mechanism for building images, from simple
+SPL + U-Boot combinations, to more complex arrangements with many parts.
+
+
+What it does
+------------
+
+Binman reads your board's device tree and finds a node which describes the
+required image layout. It uses this to work out what to place where. The
+output file normally contains the device tree, so it is in principle possible
+to read an image and extract its constituent parts.
+
+
+Features
+--------
+
+So far binman is pretty simple. It supports binary blobs, such as 'u-boot',
+'spl' and 'fdt'. It supports empty entries (such as setting to 0xff). It can
+place entries at a fixed location in the image, or fit them together with
+suitable padding and alignment. It provides a way to process binaries before
+they are included, by adding a Python plug-in. The device tree is available
+to U-Boot at run-time so that the images can be interpreted.
+
+Binman does not yet update the device tree with the final location of
+everything when it is done. A simple C structure could be generated for
+constrained environments like SPL (using dtoc) but this is also not
+implemented.
+
+Binman can also support incorporating filesystems in the image if required.
+For example x86 platforms may use CBFS in some cases.
+
+Binman is intended for use with U-Boot but is designed to be general enough
+to be useful in other image-packaging situations.
+
+
+Motivation
+----------
+
+Packaging of firmware is quite a different task from building the various
+parts. In many cases the various binaries which go into the image come from
+separate build systems. For example, ARM Trusted Firmware is used on ARMv8
+devices but is not built in the U-Boot tree. If a Linux kernel is included
+in the firmware image, it is built elsewhere.
+
+It is of course possible to add more and more build rules to the U-Boot
+build system to cover these cases. It can shell out to other Makefiles and
+build scripts. But it seems better to create a clear divide between building
+software and packaging it.
+
+At present this is handled by manual instructions, different for each board,
+on how to create images that will boot. By turning these instructions into a
+standard format, we can support making valid images for any board without
+manual effort, lots of READMEs, etc.
+
+Benefits:
+- Each binary can have its own build system and tool chain without creating
+any dependencies between them
+- Avoids the need for a single-shot build: individual parts can be updated
+and brought in as needed
+- Provides for a standard image description available in the build and at
+run-time
+- SoC-specific image-signing tools can be accomodated
+- Avoids cluttering the U-Boot build system with image-building code
+- The image description is automatically available at run-time in U-Boot,
+SPL. It can be made available to other software also
+- The image description is easily readable (it's a text file in device-tree
+format) and permits flexible packing of binaries
+
+
+Terminology
+-----------
+
+Binman uses the following terms:
+
+- image - an output file containing a firmware image
+- binary - an input binary that goes into the image
+
+
+Relationship to FIT
+-------------------
+
+FIT is U-Boot's official image format. It supports multiple binaries with
+load / execution addresses, compression. It also supports verification
+through hashing and RSA signatures.
+
+FIT was originally designed to support booting a Linux kernel (with an
+optional ramdisk) and device tree chosen from various options in the FIT.
+Now that U-Boot supports configuration via device tree, it is possible to
+load U-Boot from a FIT, with the device tree chosen by SPL.
+
+Binman considers FIT to be one of the binaries it can place in the image.
+
+Where possible it is best to put as much as possible in the FIT, with binman
+used to deal with cases not covered by FIT. Examples include initial
+execution (since FIT itself does not have an executable header) and dealing
+with device boundaries, such as the read-only/read-write separation in SPI
+flash.
+
+For U-Boot, binman should not be used to create ad-hoc images in place of
+FIT.
+
+
+Relationship to mkimage
+-----------------------
+
+The mkimage tool provides a means to create a FIT. Traditionally it has
+needed an image description file: a device tree, like binman, but in a
+different format. More recently it has started to support a '-f auto' mode
+which can generate that automatically.
+
+More relevant to binman, mkimage also permits creation of many SoC-specific
+image types. These can be listed by running 'mkimage -T list'. Examples
+include 'rksd', the Rockchip SD/MMC boot format. The mkimage tool is often
+called from the U-Boot build system for this reason.
+
+Binman considers the output files created by mkimage to be binary blobs
+which it can place in an image. Binman does not replace the mkimage tool or
+this purpose. It would be possible in some situtions to create a new entry
+type for the images in mkimage, but this would not add functionality. It
+seems better to use the mkiamge tool to generate binaries and avoid blurring
+the boundaries between building input files (mkimage) and packaging then
+into a final image (binman).
+
+
+Example use of binman in U-Boot
+-------------------------------
+
+Binman aims to replace some of the ad-hoc image creation in the U-Boot
+build system.
+
+Consider sunxi. It has the following steps:
+
+1. It uses a custom mksunxiboot tool to build an SPL image called
+sunxi-spl.bin. This should probably move into mkimage.
+
+2. It uses mkimage to package U-Boot into a legacy image file (so that it can
+hold the load and execution address) called u-boot.img.
+
+3. It builds a final output image called u-boot-sunxi-with-spl.bin which
+consists of sunxi-spl.bin, some padding and u-boot.img.
+
+Binman is intended to replace the last step. The U-Boot build system builds
+u-boot.bin and sunxi-spl.bin. Binman can then take over creation of
+sunxi-spl.bin (by calling mksunxiboot, or hopefully one day mkimage). In any
+case, it would then create the image from the component parts.
+
+This simplifies the U-Boot Makefile somewhat, since various pieces of logic
+can be replaced by a call to binman.
+
+
+Example use of binman for x86
+-----------------------------
+
+In most cases x86 images have a lot of binary blobs, 'black-box' code
+provided by Intel which must be run for the platform to work. Typically
+these blobs are not relocatable and must be placed at fixed areas in the
+firmare image.
+
+Currently this is handled by ifdtool, which places microcode, FSP, MRC, VGA
+BIOS, reference code and Intel ME binaries into a u-boot.rom file.
+
+Binman is intended to replace all of this, with ifdtool left to handle only
+the configuration of the Intel-format descriptor.
+
+
+Running binman
+--------------
+
+Type:
+
+ binman -b <board_name>
+
+to build an image for a board. The board name is the same name used when
+configuring U-Boot (e.g. for sandbox_defconfig the board name is 'sandbox').
+Binman assumes that the input files for the build are in ../b/<board_name>.
+
+Or you can specify this explicitly:
+
+ binman -I <build_path>
+
+where <build_path> is the build directory containing the output of the U-Boot
+build.
+
+(Future work will make this more configurable)
+
+In either case, binman picks up the device tree file (u-boot.dtb) and looks
+for its instructions in the 'binman' node.
+
+Binman has a few other options which you can see by running 'binman -h'.
+
+
+Image description format
+------------------------
+
+The binman node is called 'binman'. An example image description is shown
+below:
+
+ binman {
+ filename = "u-boot-sunxi-with-spl.bin";
+ pad-byte = <0xff>;
+ blob {
+ filename = "spl/sunxi-spl.bin";
+ };
+ u-boot {
+ pos = <CONFIG_SPL_PAD_TO>;
+ };
+ };
+
+
+This requests binman to create an image file called u-boot-sunxi-with-spl.bin
+consisting of a specially formatted SPL (spl/sunxi-spl.bin, built by the
+normal U-Boot Makefile), some 0xff padding, and a U-Boot legacy image. The
+padding comes from the fact that the second binary is placed at
+CONFIG_SPL_PAD_TO. If that line were omitted then the U-Boot binary would
+immediately follow the SPL binary.
+
+The binman node describes an image. The sub-nodes describe entries in the
+image. Each entry represents a region within the overall image. The name of
+the entry (blob, u-boot) tells binman what to put there. For 'blob' we must
+provide a filename. For 'u-boot', binman knows that this means 'u-boot.bin'.
+
+Entries are normally placed into the image sequentially, one after the other.
+The image size is the total size of all entries. As you can see, you can
+specify the start position of an entry using the 'pos' property.
+
+Note that due to a device tree requirement, all entries must have a unique
+name. If you want to put the same binary in the image multiple times, you can
+use any unique name, with the 'type' property providing the type.
+
+The attributes supported for entries are described below.
+
+pos:
+ This sets the position of an entry within the image. The first byte
+ of the image is normally at position 0. If 'pos' is not provided,
+ binman sets it to the end of the previous region, or the start of
+ the image's entry area (normally 0) if there is no previous region.
+
+align:
+ This sets the alignment of the entry. The entry position is adjusted
+ so that the entry starts on an aligned boundary within the image. For
+ example 'align = <16>' means that the entry will start on a 16-byte
+ boundary. Alignment shold be a power of 2. If 'align' is not
+ provided, no alignment is performed.
+
+size:
+ This sets the size of the entry. The contents will be padded out to
+ this size. If this is not provided, it will be set to the size of the
+ contents.
+
+pad-before:
+ Padding before the contents of the entry. Normally this is 0, meaning
+ that the contents start at the beginning of the entry. This can be
+ offset the entry contents a little. Defaults to 0.
+
+pad-after:
+ Padding after the contents of the entry. Normally this is 0, meaning
+ that the entry ends at the last byte of content (unless adjusted by
+ other properties). This allows room to be created in the image for
+ this entry to expand later. Defaults to 0.
+
+align-size:
+ This sets the alignment of the entry size. For example, to ensure
+ that the size of an entry is a multiple of 64 bytes, set this to 64.
+ If 'align-size' is not provided, no alignment is performed.
+
+align-end:
+ This sets the alignment of the end of an entry. Some entries require
+ that they end on an alignment boundary, regardless of where they
+ start. If 'align-end' is not provided, no alignment is performed.
+
+ Note: This is not yet implemented in binman.
+
+filename:
+ For 'blob' types this provides the filename containing the binary to
+ put into the entry. If binman knows about the entry type (like
+ u-boot-bin), then there is no need to specify this.
+
+type:
+ Sets the type of an entry. This defaults to the entry name, but it is
+ possible to use any name, and then add (for example) 'type = "u-boot"'
+ to specify the type.
+
+
+The attributes supported for images are described below. Several are similar
+to those for entries.
+
+size:
+ Sets the image size in bytes, for example 'size = <0x100000>' for a
+ 1MB image.
+
+align-size:
+ This sets the alignment of the image size. For example, to ensure
+ that the image ends on a 512-byte boundary, use 'align-size = <512>'.
+ If 'align-size' is not provided, no alignment is performed.
+
+pad-before:
+ This sets the padding before the image entries. The first entry will
+ be positionad after the padding. This defaults to 0.
+
+pad-after:
+ This sets the padding after the image entries. The padding will be
+ placed after the last entry. This defaults to 0.
+
+pad-byte:
+ This specifies the pad byte to use when padding in the image. It
+ defaults to 0. To use 0xff, you would add 'pad-byte = <0xff>'.
+
+filename:
+ This specifies the image filename. It defaults to 'image.bin'.
+
+sort-by-pos:
+ This causes binman to reorder the entries as needed to make sure they
+ are in increasing positional order. This can be used when your entry
+ order may not match the positional order. A common situation is where
+ the 'pos' properties are set by CONFIG options, so their ordering is
+ not known a priori.
+
+ This is a boolean property so needs no value. To enable it, add a
+ line 'sort-by-pos;' to your description.
+
+multiple-images:
+ Normally only a single image is generated. To create more than one
+ image, put this property in the binman node. For example, this will
+ create image1.bin containing u-boot.bin, and image2.bin containing
+ both spl/u-boot-spl.bin and u-boot.bin:
+
+ binman {
+ multiple-images;
+ image1 {
+ u-boot {
+ };
+ };
+
+ image2 {
+ spl {
+ };
+ u-boot {
+ };
+ };
+ };
+
+end-at-4gb:
+ For x86 machines the ROM positions start just before 4GB and extend
+ up so that the image finished at the 4GB boundary. This boolean
+ option can be enabled to support this. The image size must be
+ provided so that binman knows when the image should start. For an
+ 8MB ROM, the position of the first entry would be 0xfff80000 with
+ this option, instead of 0 without this option.
+
+
+Examples of the above options can be found in the tests. See the
+tools/binman/test directory.
+
+
+Order of image creation
+-----------------------
+
+Image creation proceeds in the following order, for each entry in the image.
+
+1. GetEntryContents() - the contents of each entry are obtained, normally by
+reading from a file. This calls the Entry.ObtainContents() to read the
+contents. The default version of Entry.ObtainContents() calls
+Entry.GetDefaultFilename() and then reads that file. So a common mechanism
+to select a file to read is to override that function in the subclass. The
+functions must return True when they have read the contents. Binman will
+retry calling the functions a few times if False is returned, allowing
+dependencies between the contents of different entries.
+
+2. GetEntryPositions() - calls Entry.GetPositions() for each entry. This can
+return a dict containing entries that need updating. The key should be the
+entry name and the value is a tuple (pos, size). This allows an entry to
+provide the position and size for other entries. The default implementation
+of GetEntryPositions() returns {}.
+
+3. PackEntries() - calls Entry.Pack() which figures out the position and
+size of an entry. The 'current' image position is passed in, and the function
+returns the position immediately after the entry being packed. The default
+implementation of Pack() is usually sufficient.
+
+4. CheckSize() - checks that the contents of all the entries fits within
+the image size. If the image does not have a defined size, the size is set
+large enough to hold all the entries.
+
+5. CheckEntries() - checks that the entries do not overlap, nor extend
+outside the image.
+
+6. ProcessEntryContents() - this calls Entry.ProcessContents() on each entry.
+The default implementatoin does nothing. This can be overriden to adjust the
+contents of an entry in some way. For example, it would be possible to create
+an entry containing a hash of the contents of some other entries. At this
+stage the position and size of entries should not be adjusted.
+
+7. BuildImage() - builds the image and writes it to a file. This is the final
+step.
+
+
+Advanced Features / Technical docs
+----------------------------------
+
+The behaviour of entries is defined by the Entry class. All other entries are
+a subclass of this. An important subclass is Entry_blob which takes binary
+data from a file and places it in the entry. In fact most entry types are
+subclasses of Entry_blob.
+
+Each entry type is a separate file in the tools/binman/etype directory. Each
+file contains a class called Entry_<type> where <type> is the entry type.
+New entry types can be supported by adding new files in that directory.
+These will automatically be detected by binman when needed.
+
+Entry properties are documented in entry.py. The entry subclasses are free
+to change the values of properties to support special behaviour. For example,
+when Entry_blob loads a file, it sets content_size to the size of the file.
+Entry classes can adjust other entries. For example, an entry that knows
+where other entries should be positioned can set up those entries' positions
+so they don't need to be set in the binman decription. It can also adjust
+entry contents.
+
+Most of the time such essoteric behaviour is not needed, but it can be
+essential for complex images.
+
+
+History / Credits
+-----------------
+
+Binman takes a lot of inspiration from a Chrome OS tool called
+'cros_bundle_firmware', which I wrote some years ago. That tool was based on
+a reasonably simple and sound design but has expanded greatly over the
+years. In particular its handling of x86 images is convoluted.
+
+Quite a few lessons have been learned which are hopefully be applied here.
+
+
+Design notes
+------------
+
+On the face of it, a tool to create firmware images should be fairly simple:
+just find all the input binaries and place them at the right place in the
+image. The difficulty comes from the wide variety of input types (simple
+flat binaries containing code, packaged data with various headers), packing
+requirments (alignment, spacing, device boundaries) and other required
+features such as hierarchical images.
+
+The design challenge is to make it easy to create simple images, while
+allowing the more complex cases to be supported. For example, for most
+images we don't much care exactly where each binary ends up, so we should
+not have to specify that unnecessarily.
+
+New entry types should aim to provide simple usage where possible. If new
+core features are needed, they can be added in the Entry base class.
+
+
+To do
+-----
+
+Some ideas:
+- Fill out the device tree to include the final position and size of each
+ entry (since the input file may not always specify these)
+- Use of-platdata to make the information available to code that is unable
+ to use device tree (such as a very small SPL image)
+- Write an image map to a text file
+- Allow easy building of images by specifying just the board name
+- Produce a full Python binding for libfdt (for upstream)
+- Add an option to decode an image into the constituent binaries
+- Suppoort hierarchical images (packing of binaries into another binary
+ which is then placed in the image)
+- Support building an image for a board (-b) more completely, with a
+ configurable build directory
+- Consider making binman work with buildman, although if it is used in the
+ Makefile, this will be automatic
+- Implement align-end
+
+--
+Simon Glass <sjg@chromium.org>
+7/7/2016