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binman: Add more documentation about binman usage
This is an attempt to answer the comments provided by Xavier [1]. [1] https://lore.kernel.org/all/Yulcol7HpTHtjXTX@begut/ Signed-off-by: Simon Glass <sjg@chromium.org> Acked-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
This commit is contained in:
Simon Glass
Heinrich Schuchardt
parent
228c9b8629
commit
7d6fadef84
@ -56,6 +56,7 @@ quiet_cmd_sphinx = SPHINX $@ --> file://$(abspath $(BUILDDIR)/$3/$4)
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PYTHONDONTWRITEBYTECODE=1 \
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BUILDDIR=$(abspath $(BUILDDIR)) SPHINX_CONF=$(abspath $(srctree)/$(src)/$5/$(SPHINX_CONF)) \
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$(SPHINXBUILD) \
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-j$(shell nproc) \
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-b $2 \
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-c $(abspath $(srctree)/$(src)) \
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-d $(abspath $(BUILDDIR)/.doctrees/$3) \
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@ -42,7 +42,7 @@ the devicetree description of the image.
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Binman is designed primarily for use with U-Boot and associated binaries such
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as ARM Trusted Firmware, but it is suitable for use with other projects, such
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as Zephyr. Binman also provides facilities useful in Chromium OS, such as CBFS,
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vblocks and and the like.
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vblocks and the like.
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Binman provides a way to process binaries before they are included, by adding a
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Python plug-in.
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@ -118,6 +118,10 @@ flash.
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For U-Boot, binman should not be used to create ad-hoc images in place of
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FIT.
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Note that binman can itself create a FIT. This helps to move mkimage
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invocations out of the Makefile and into binman image descriptions. It also
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helps by removing the need for ad-hoc tools like `make_fit_atf.py`.
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Relationship to mkimage
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-----------------------
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@ -140,6 +144,9 @@ seems better to use the mkimage tool to generate binaries and avoid blurring
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the boundaries between building input files (mkimage) and packaging then
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into a final image (binman).
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Note that binman can itself invoke mkimage. This helps to move mkimage
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invocations out of the Makefile and into binman image descriptions.
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Using binman
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============
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@ -170,6 +177,164 @@ This simplifies the U-Boot Makefile somewhat, since various pieces of logic
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can be replaced by a call to binman.
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Invoking binman within U-Boot
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-----------------------------
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Within U-Boot, binman is invoked by the build system, i.e. when you type 'make'
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or use buildman to build U-Boot. There is no need to run binman independently
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during development. Everything happens automatically and is set up for your
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SoC or board so that binman produced the right things.
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The general policy is that the Makefile builds all the binaries in INPUTS-y
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(the 'inputs' rule), then binman is run to produce the final images (the 'all'
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rule).
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There should be only one invocation of binman in Makefile, the very last step
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that pulls everything together. At present there are some arch-specific
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invocations as well, but these should be dropped when those architectures are
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converted to use binman properly.
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As above, the term 'binary' is used for something in INPUTS-y and 'image' is
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used for the things that binman creates. So the binaries are inputs to the
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image(s) and it is the image that is actually loaded on the board.
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Again, at present, there are a number of things created in Makefile which should
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be done by binman (when we get around to it), like `u-boot-ivt.img`,
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`lpc32xx-spl.img`, `u-boot-with-nand-spl.imx`, `u-boot-spl-padx4.sfp` and
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`u-boot-mtk.bin`, just to pick on a few. When completed this will remove about
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400 lines from `Makefile`.
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Since binman is invoked only once, it must of course create all the images that
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are needed, in that one invocation. It does this by working through the image
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descriptions one by one, collecting the input binaries, processing them as
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needed and producing the final images.
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The same binaries may be used by multiple images. For example binman may be used
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to produce an SD-card image and a SPI-flash image. In this case the binaries
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going into the process are the same, but binman produces slightly different
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images in each case.
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For some SoCs, U-Boot is not the only project that produces the necessary
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binaries. For example, ARM Trusted Firmware (ATF) is a project that produces
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binaries which must be incorporate, such as `bl31.elf` or `bl31.bin`. For this
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to work you must have built ATF before you build U-Boot and you must tell U-Boot
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where to find the bl31 image, using the BL31 environment variable.
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How do you know how to incorporate ATF? It is handled by the atf-bl31 entry type
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(etype). An etype is an implementation of reading a binary into binman, in this
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case the `bl31.bin` file. When you build U-Boot but do not set the BL31
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environment variable, binman provides a help message, which comes from
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`missing-blob-help`::
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See the documentation for your board. You may need to build ARM Trusted
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Firmware and build with BL31=/path/to/bl31.bin
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The mechanism by which binman is advised of this is also in the Makefile. See
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the `-a atf-bl31-path=${BL31}` piece in `cmd_binman`. This tells binman to
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set the EntryArg `atf-bl31-path` to the value of the `BL31` environment
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variable. Within binman, this EntryArg is picked up by the `Entry_atf_bl31`
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etype. An EntryArg is simply an argument to the entry. The `atf-bl31-path`
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name is documented in :ref:`etype_atf_bl31`.
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Invoking binman outside U-Boot
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------------------------------
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While binman is invoked from within the U-Boot build system, it is also possible
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to invoke it separately. This is typically used in a production build system,
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where signing is completed (with real keys) and any missing binaries are
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provided.
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For example, for build testing there is no need to provide a real signature,
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nor is there any need to provide a real ATF BL31 binary (for example). These can
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be added later by invoking binman again, providing all the required inputs
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from the first time, plus any that were missing or placeholders.
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So in practice binman is often used twice:
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- once within the U-Boot build system, for development and testing
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- again outside U-Boot to assembly and final production images
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While the same input binaries are used in each case, you will of course you will
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need to create your own binman command line, similar to that in `cmd_binman` in
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the Makefile. You may find the -I and --toolpath options useful. The
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device tree file is provided to binman in binary form, so there is no need to
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have access to the original `.dts` sources.
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Assembling the image description
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--------------------------------
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Since binman uses the device tree for its image description, you can use the
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same files that describe your board's hardware to describe how the image is
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assembled. Typically the images description is in a common file used by all
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boards with a particular SoC (e.g. `imx8mp-u-boot.dtsi`).
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Where a particular boards needs to make changes, it can override properties in
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the SoC file, just as it would for any other device tree property. It can also
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add a image that is specific to the board.
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Another way to control the image description to make use of CONFIG options in
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the description. For example, if the start offset of a particular entry varies
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by board, you can add a Kconfig for that and reference it in the description::
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u-boot-spl {
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};
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fit {
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offset = <CONFIG_SPL_PAD_TO>;
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...
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};
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The SoC can provide a default value but boards can override that as needed and
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binman will take care of it.
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It is even possible to control which entries appear in the image, by using the
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C preprocessor::
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#ifdef CONFIG_HAVE_MRC
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intel-mrc {
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offset = <CONFIG_X86_MRC_ADDR>;
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};
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#endif
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Only boards which enable `HAVE_MRC` will include this entry.
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Obviously a similar approach can be used to control which images are produced,
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with a Kconfig option to enable a SPI image, for example. However there is
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generally no harm in producing an image that is not used. If a board uses MMC
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but not SPI, but the SoC supports booting from both, then both images can be
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produced, with only on or other being used by particular boards. This can help
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reduce the need for having multiple defconfig targets for a board where the
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only difference is the boot media, enabling / disabling secure boot, etc.
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Of course you can use the device tree itself to pass any board-specific
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information that is needed by U-Boot at runtime (see binman_syms_ for how to
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make binman insert these values directly into executables like SPL).
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There is one more way this can be done: with individual .dtsi files for each
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image supported by the SoC. Then the board `.dts` file can include the ones it
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wants. This is not recommended, since it is likely to be difficult to maintain
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and harder to understand the relationship between the different boards.
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Producing images for multiple boards
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------------------------------------
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When invoked within U-Boot, binman only builds a single set of images, for
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the chosen board. This is set by the `CONFIG_DEFAULT_DEVICE_TREE` option.
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However, U-Boot generally builds all the device tree files associated with an
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SoC. These are written to the (e.g. for ARM) `arch/arm/dts` directory. Each of
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these contains the full binman description for that board. Often the best
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approach is to build a single image that includes all these device tree binaries
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and allow SPL to select the correct one on boot.
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However, it is also possible to build separate images for each board, simply by
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invoking binman multiple times, once for each device tree file, using a
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different output directory. This will produce one set of images for each board.
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Example use of binman for x86
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-----------------------------
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@ -188,19 +353,25 @@ the configuration of the Intel-format descriptor.
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Installing binman
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-----------------
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First install prerequisites, e.g::
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First install prerequisites, e.g:
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.. code-block:: bash
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sudo apt-get install python-pyelftools python3-pyelftools lzma-alone \
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liblz4-tool
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You can run binman directly if you put it on your PATH. But if you want to
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install into your `~/.local` Python directory, use::
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install into your `~/.local` Python directory, use:
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.. code-block:: bash
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pip install tools/patman tools/dtoc tools/binman
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Note that binman makes use of libraries from patman and dtoc, which is why these
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need to be installed. Also you need `libfdt` and `pylibfdt` which can be
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installed like this::
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installed like this:
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.. code-block:: bash
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git clone git://git.kernel.org/pub/scm/utils/dtc/dtc.git
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cd dtc
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@ -209,7 +380,9 @@ installed like this::
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This installs the `libfdt.so` library into `~/lib` so you can use
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`LD_LIBRARY_PATH=~/lib` when running binman. If you want to install it in the
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system-library directory, replace the last line with::
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system-library directory, replace the last line with:
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.. code-block:: bash
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make NO_PYTHON=1 PREFIX=/ install
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@ -218,14 +391,20 @@ Running binman
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Type::
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.. code-block: bash
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make NO_PYTHON=1 PREFIX=/ install
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binman build -b <board_name>
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to build an image for a board. The board name is the same name used when
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configuring U-Boot (e.g. for sandbox_defconfig the board name is 'sandbox').
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Binman assumes that the input files for the build are in ../b/<board_name>.
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Or you can specify this explicitly::
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Or you can specify this explicitly:
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.. code-block:: bash
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make NO_PYTHON=1 PREFIX=/ install
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binman build -I <build_path>
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where <build_path> is the build directory containing the output of the U-Boot
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@ -254,6 +433,7 @@ file, typically <soc>-u-boot.dtsi, where <soc> is your CONFIG_SYS_SOC value.
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You can use other, more specific CONFIG options - see 'Automatic .dtsi
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inclusion' below.
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.. _binman_syms:
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Access to binman entry offsets at run time (symbols)
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----------------------------------------------------
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@ -264,13 +444,17 @@ is useful to be able to find the location of U-Boot so that it can be executed
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when SPL is finished.
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Binman allows you to declare symbols in the SPL image which are filled in
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with their correct values during the build. For example::
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with their correct values during the build. For example:
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.. code-block:: c
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binman_sym_declare(ulong, u_boot_any, image_pos);
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declares a ulong value which will be assigned to the image-pos of any U-Boot
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image (u-boot.bin, u-boot.img, u-boot-nodtb.bin) that is present in the image.
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You can access this value with something like::
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You can access this value with something like:
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.. code-block:: c
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ulong u_boot_offset = binman_sym(ulong, u_boot_any, image_pos);
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