Re: [PATCH v7 2/2] arm64: boot: Support Flat Image Tree

[Nicolas Schier]

Simon,

thanks for the patch!  Below are some nitpicks and bike-shedding 
questions.

On Wed 29 Nov 2023 10:21:53 GMT, Simon Glass wrote:
> Add a script which produces a Flat Image Tree (FIT), a single file
> containing the built kernel and associated devicetree files.
> Compression defaults to gzip which gives a good balance of size and
> performance.
> 
> The files compress from about 86MB to 24MB using this approach.
> 
> The FIT can be used by bootloaders which support it, such as U-Boot
> and Linuxboot. It permits automatic selection of the correct
> devicetree, matching the compatible string of the running board with
> the closest compatible string in the FIT. There is no need for
> filenames or other workarounds.

Have you thought about updating the arch/mips ITB rules to also use the 
new scripts/make_fit.py?  Or is the FIT/ITB format for mips different 
from the one for arm64?

> Add a 'make image.fit' build target for arm64, as well.
> 
> The FIT can be examined using 'dumpimage -l'.
> 
> This features requires pylibfdt (use 'pip install libfdt'). It also
> requires compression utilities for the algorithm being used. Supported
> compression options are the same as the Image.xxx files. For now there
> is no way to change the compression other than by editing the rule for
> $(obj)/image.fit
> 
> While FIT supports a ramdisk / initrd, no attempt is made to support
> this here, since it must be built separately from the Linux build.
> 
> Signed-off-by: Simon Glass <sjg@xxxxxxxxxxxx>
> ---
> 
> Changes in v7:
> - Add Image as a dependency of image.fit
> - Drop kbuild tag
> - Add dependency on dtbs
> - Drop unnecessary path separator for dtbs
> - Rebase to -next
> 
> Changes in v5:
> - Drop patch previously applied
> - Correct compression rule which was broken in v4
> 
> Changes in v4:
> - Use single quotes for UIMAGE_NAME
> 
> Changes in v3:
> - Drop temporary file image.itk
> - Drop patch 'Use double quotes for image name'
> - Drop double quotes in use of UIMAGE_NAME
> - Drop unnecessary CONFIG_EFI_ZBOOT condition for help
> - Avoid hard-coding "arm64" for the DT architecture
> 
> Changes in v2:
> - Drop patch previously applied
> - Add .gitignore file
> - Move fit rule to Makefile.lib using an intermediate file
> - Drop dependency on CONFIG_EFI_ZBOOT
> - Pick up .dtb files separately from the kernel
> - Correct pylint too-many-args warning for write_kernel()
> - Include the kernel image in the file count
> - Add a pointer to the FIT spec and mention of its wide industry usage
> - Mention the kernel version in the FIT description
> 
>  MAINTAINERS                |   7 +
>  arch/arm64/Makefile        |   9 +-
>  arch/arm64/boot/.gitignore |   1 +
>  arch/arm64/boot/Makefile   |   6 +-
>  scripts/Makefile.lib       |  13 ++
>  scripts/make_fit.py        | 289 +++++++++++++++++++++++++++++++++++++
>  6 files changed, 322 insertions(+), 3 deletions(-)
>  create mode 100755 scripts/make_fit.py
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 14587be87a33..d609f0e8deb3 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1585,6 +1585,13 @@ F:	Documentation/process/maintainer-soc*.rst
>  F:	arch/arm/boot/dts/Makefile
>  F:	arch/arm64/boot/dts/Makefile
>  
> +ARM64 FIT SUPPORT
> +M:	Simon Glass <sjg@xxxxxxxxxxxx>
> +L:	linux-arm-kernel@xxxxxxxxxxxxxxxxxxx (moderated for non-subscribers)
> +S:	Maintained
> +F:	arch/arm64/boot/Makefile
> +F:	scripts/make_fit.py
> +

I'm afraid that the location does not match the requested sorting, it 
should be right before "ARM64 PORT".

>  ARM ARCHITECTED TIMER DRIVER
>  M:	Mark Rutland <mark.rutland@xxxxxxx>
>  M:	Marc Zyngier <maz@xxxxxxxxxx>
> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> index 1bd4fae6e806..18e092de7cdb 100644
> --- a/arch/arm64/Makefile
> +++ b/arch/arm64/Makefile
> @@ -36,6 +36,8 @@ ifeq ($(CONFIG_BROKEN_GAS_INST),y)
>  $(warning Detected assembler with broken .inst; disassembly will be unreliable)
>  endif
>  
> +KBUILD_DTBS      := dtbs

Might you want to use tabs here as in the lines below?

> +
>  KBUILD_CFLAGS	+= -mgeneral-regs-only	\
>  		   $(compat_vdso) $(cc_has_k_constraint)
>  KBUILD_CFLAGS	+= $(call cc-disable-warning, psabi)
> @@ -150,7 +152,7 @@ libs-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
>  # Default target when executing plain make
>  boot		:= arch/arm64/boot
>  
> -BOOT_TARGETS	:= Image vmlinuz.efi
> +BOOT_TARGETS	:= Image vmlinuz.efi image.fit
>  
>  PHONY += $(BOOT_TARGETS)
>  
> @@ -162,7 +164,9 @@ endif
>  
>  all:	$(notdir $(KBUILD_IMAGE))
>  
> -vmlinuz.efi: Image
> +image.fit: $(KBUILD_DTBS)
> +
> +vmlinuz.efi image.fit: Image
>  $(BOOT_TARGETS): vmlinux
>  	$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
>  
> @@ -215,6 +219,7 @@ virtconfig:
>  define archhelp
>    echo  '* Image.gz      - Compressed kernel image (arch/$(ARCH)/boot/Image.gz)'
>    echo  '  Image         - Uncompressed kernel image (arch/$(ARCH)/boot/Image)'
> +  echo  '  image.fit     - Flat Image Tree (arch/$(ARCH)/boot/image.fit)'
>    echo  '  install       - Install uncompressed kernel'
>    echo  '  zinstall      - Install compressed kernel'
>    echo  '                  Install using (your) ~/bin/installkernel or'
> diff --git a/arch/arm64/boot/.gitignore b/arch/arm64/boot/.gitignore
> index af5dc61f8b43..abaae9de1bdd 100644
> --- a/arch/arm64/boot/.gitignore
> +++ b/arch/arm64/boot/.gitignore
> @@ -2,3 +2,4 @@
>  Image
>  Image.gz
>  vmlinuz*
> +image.fit
> diff --git a/arch/arm64/boot/Makefile b/arch/arm64/boot/Makefile
> index 1761f5972443..8d591fda078f 100644
> --- a/arch/arm64/boot/Makefile
> +++ b/arch/arm64/boot/Makefile
> @@ -16,7 +16,8 @@
>  
>  OBJCOPYFLAGS_Image :=-O binary -R .note -R .note.gnu.build-id -R .comment -S
>  
> -targets := Image Image.bz2 Image.gz Image.lz4 Image.lzma Image.lzo Image.zst
> +targets := Image Image.bz2 Image.gz Image.lz4 Image.lzma Image.lzo \
> +	Image.zst image.fit

Do you introduce the first lower-case image.* target by intention?  
(All others have a capital 'I'.)

>  
>  $(obj)/Image: vmlinux FORCE
>  	$(call if_changed,objcopy)
> @@ -39,6 +40,9 @@ $(obj)/Image.lzo: $(obj)/Image FORCE
>  $(obj)/Image.zst: $(obj)/Image FORCE
>  	$(call if_changed,zstd)
>  
> +$(obj)/image.fit: $(obj)/Image FORCE
> +	$(call cmd,fit,gzip)
> +
>  EFI_ZBOOT_PAYLOAD	:= Image
>  EFI_ZBOOT_BFD_TARGET	:= elf64-littleaarch64
>  EFI_ZBOOT_MACH_TYPE	:= ARM64
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index 1a965fe68e01..e1c06ca3c847 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -496,6 +496,19 @@ quiet_cmd_uimage = UIMAGE  $@
>  			-a $(UIMAGE_LOADADDR) -e $(UIMAGE_ENTRYADDR) \
>  			-n '$(UIMAGE_NAME)' -d $< $@
>  
> +# Flat Image Tree (FIT)
> +# This allows for packaging of a kernel and all devicetrees files, using
> +# compression.
> +# ---------------------------------------------------------------------------
> +
> +MAKE_FIT := $(srctree)/scripts/make_fit.py
> +
> +quiet_cmd_fit = FIT     $@
> +      cmd_fit = $(MAKE_FIT) -f $@ --arch $(UIMAGE_ARCH) --os linux \
> +			--name '$(UIMAGE_NAME)' \
> +			--compress $(UIMAGE_COMPRESSION) -k $< \
> +			$(dir $<)dts

Alternatively, you could use '$(<D)/dts' instead of '$(dir $<)dts' 
(bike-shedding).

> +
>  # XZ
>  # ---------------------------------------------------------------------------
>  # Use xzkern to compress the kernel image and xzmisc to compress other things.
> diff --git a/scripts/make_fit.py b/scripts/make_fit.py
> new file mode 100755
> index 000000000000..e1059825de9c
> --- /dev/null
> +++ b/scripts/make_fit.py
> @@ -0,0 +1,289 @@
> +#!/usr/bin/env python3
> +# SPDX-License-Identifier: GPL-2.0+
> +#
> +# Copyright 2023 Google LLC
> +# Written by Simon Glass <sjg@xxxxxxxxxxxx>
> +#
> +
> +"""Build a FIT containing a lot of devicetree files
> +
> +Usage:
> +    make_fit.py -A arm64 -n 'Linux-6.6' -O linux
> +        -f arch/arm64/boot/image.fit -k /tmp/kern/arch/arm64/boot/image.itk
> +        /tmp/kern/arch/arm64/boot/dts/ -E -c gzip
> +
> +Creates a FIT containing the supplied kernel and a directory containing the
> +devicetree files.
> +
> +Use -E to generate an external FIT (where the data is placed after the
> +FIT data structure). This allows parsing of the data without loading
> +the entire FIT.
> +
> +Use -c to compress the data, using bzip2, gzip, lz4, lzma, lzo and
> +zstd

Lost a dot at EOL?

> +
> +The resulting FIT can be booted by bootloaders which support FIT, such
> +as U-Boot, Linuxboot, Tianocore, etc.
> +
> +Note that this tool does not yet support adding a ramdisk / initrd.
> +"""
> +
> +import argparse
> +import collections
> +import os
> +import subprocess
> +import sys
> +import tempfile
> +import time
> +
> +import libfdt
> +
> +
> +# Tool extension and the name of the command-line tools
> +CompTool = collections.namedtuple('CompTool', 'ext,tools')
> +
> +COMP_TOOLS = {
> +    'bzip2': CompTool('.bz2', 'bzip2'),
> +    'gzip': CompTool('.gz', 'pigz,gzip'),
> +    'lz4': CompTool('.lz4', 'lz4'),
> +    'lzma': CompTool('.lzma', 'lzma'),
> +    'lzo': CompTool('.lzo', 'lzop'),
> +    'zstd': CompTool('.zstd', 'zstd'),
> +}
> +
> +def parse_args():
> +    """Parse the program ArgumentParser
> +
> +    Returns:
> +        Namespace object containing the arguments
> +    """
> +    epilog = 'Build a FIT from a directory tree containing .dtb files'
> +    parser = argparse.ArgumentParser(epilog=epilog)
> +    parser.add_argument('-A', '--arch', type=str, required=True,
> +          help='Specifies the architecture')
> +    parser.add_argument('-c', '--compress', type=str, default='none',
> +          help='Specifies the compression')
> +    parser.add_argument('-E', '--external', action='store_true',
> +          help='Convert the FIT to use external data')
> +    parser.add_argument('-n', '--name', type=str, required=True,
> +          help='Specifies the name')
> +    parser.add_argument('-O', '--os', type=str, required=True,
> +          help='Specifies the operating system')
> +    parser.add_argument('-f', '--fit', type=str, required=True,
> +          help='Specifies the output file (.fit)')
> +    parser.add_argument('-k', '--kernel', type=str, required=True,
> +          help='Specifies the (uncompressed) kernel input file (.itk)')
> +    parser.add_argument('srcdir', type=str, nargs='*',
> +          help='Specifies the directory tree that contains .dtb files')
> +
> +    return parser.parse_args()
> +
> +def setup_fit(fsw, name):
> +    """Make a start on writing the FIT
> +
> +    Outputs the root properties and the 'images' node
> +
> +    Args:
> +        fsw (libfdt.FdtSw): Object to use for writing
> +        name (str): Name of kernel image
> +    """
> +    fsw.INC_SIZE = 65536
> +    fsw.finish_reservemap()
> +    fsw.begin_node('')
> +    fsw.property_string('description', f'{name} with devicetree set')
> +    fsw.property_u32('#address-cells', 1)
> +
> +    fsw.property_u32('timestamp', int(time.time()))
> +    fsw.begin_node('images')
> +
> +
> +def write_kernel(fsw, data, args):
> +    """Write out the kernel image
> +
> +    Writes a kernel node along with the required properties
> +
> +    Args:
> +        fsw (libfdt.FdtSw): Object to use for writing
> +        data (bytes): Data to write (possibly compressed)
> +        args (Namespace): Contains necessary strings:
> +            arch: FIT architecture, e.g. 'arm64'
> +            fit_os: Operating Systems, e.g. 'linux'
> +            name: Name of OS, e.g. 'Linux-6.6.0-rc7'
> +            compress: Compression algorithm to use, e.g. 'gzip'
> +    """
> +    with fsw.add_node('kernel'):
> +        fsw.property_string('description', args.name)
> +        fsw.property_string('type', 'kernel_noload')
> +        fsw.property_string('arch', args.arch)
> +        fsw.property_string('os', args.os)
> +        fsw.property_string('compression', args.compress)
> +        fsw.property('data', data)
> +        fsw.property_u32('load', 0)
> +        fsw.property_u32('entry', 0)
> +
> +
> +def finish_fit(fsw, entries):
> +    """Finish the FIT ready for use
> +
> +    Writes the /configurations node and subnodes
> +
> +    Args:
> +        fsw (libfdt.FdtSw): Object to use for writing
> +        entries (list of tuple): List of configurations:
> +            str: Description of model
> +            str: Compatible stringlist
> +    """
> +    fsw.end_node()
> +    seq = 0
> +    with fsw.add_node('configurations'):
> +        for model, compat in entries:
> +            seq += 1
> +            with fsw.add_node(f'conf-{seq}'):
> +                fsw.property('compatible', bytes(compat))
> +                fsw.property_string('description', model)
> +                fsw.property_string('fdt', f'fdt-{seq}')
> +                fsw.property_string('kernel', 'kernel')
> +    fsw.end_node()
> +
> +
> +def compress_data(inf, compress):
> +    """Compress data using a selected algorithm
> +
> +    Args:
> +        inf (IOBase): Filename containing the data to compress
> +        compress (str): Compression algorithm, e.g. 'gzip'
> +
> +    Return:
> +        bytes: Compressed data
> +    """
> +    if compress == 'none':
> +        return inf.read()
> +
> +    comp = COMP_TOOLS.get(compress)
> +    if not comp:
> +        raise ValueError(f"Unknown compression algorithm '{compress}'")
> +
> +    with tempfile.NamedTemporaryFile() as comp_fname:
> +        with open(comp_fname.name, 'wb') as outf:
> +            done = False
> +            for tool in comp.tools.split(','):
> +                try:
> +                    subprocess.call([tool, '-c'], stdin=inf, stdout=outf)
> +                    done = True
> +                    break
> +                except FileNotFoundError:
> +                    pass
> +            if not done:
> +                raise ValueError(f'Missing tool(s): {comp.tools}\n')
> +            with open(comp_fname.name, 'rb') as compf:
> +                comp_data = compf.read()
> +    return comp_data
> +
> +
> +def output_dtb(fsw, seq, fname, arch, compress):
> +    """Write out a single devicetree to the FIT
> +
> +    Args:
> +        fsw (libfdt.FdtSw): Object to use for writing
> +        seq (int): Sequence number (1 for first)
> +        fmame (str): Filename containing the DTB
> +        arch: FIT architecture, e.g. 'arm64'
> +        compress (str): Compressed algorithm, e.g. 'gzip'
> +
> +    Returns:
> +        tuple:
> +            str: Model name
> +            bytes: Compatible stringlist
> +    """
> +    with fsw.add_node(f'fdt-{seq}'):
> +        # Get the compatible / model information
> +        with open(fname, 'rb') as inf:
> +            data = inf.read()
> +        fdt = libfdt.FdtRo(data)
> +        model = fdt.getprop(0, 'model').as_str()
> +        compat = fdt.getprop(0, 'compatible')
> +
> +        fsw.property_string('description', model)
> +        fsw.property_string('type', 'flat_dt')
> +        fsw.property_string('arch', arch)
> +        fsw.property_string('compression', compress)
> +        fsw.property('compatible', bytes(compat))
> +
> +        with open(fname, 'rb') as inf:
> +            compressed = compress_data(inf, compress)
> +        fsw.property('data', compressed)
> +    return model, compat
> +
> +
> +def build_fit(args):
> +    """Build the FIT from the provided files and arguments
> +
> +    Args:
> +        args (Namespace): Program arguments
> +
> +    Returns:
> +        tuple:
> +            bytes: FIT data
> +            int: Number of configurations generated
> +            size: Total uncompressed size of data
> +    """
> +    fsw = libfdt.FdtSw()
> +    setup_fit(fsw, args.name)
> +    seq = 0
> +    size = 0
> +    entries = []
> +
> +    # Handle the kernel
> +    with open(args.kernel, 'rb') as inf:
> +        comp_data = compress_data(inf, args.compress)
> +    size += os.path.getsize(args.kernel)
> +    write_kernel(fsw, comp_data, args)
> +
> +    for path in args.srcdir:
> +        # Handle devicetree files
> +        if os.path.isdir(path):
> +            for dirpath, _, fnames in os.walk(path):
> +                for fname in fnames:
> +                    if os.path.splitext(fname)[1] != '.dtb':
> +                        continue
> +                    pathname = os.path.join(dirpath, fname)
> +                    seq += 1
> +                    size += os.path.getsize(pathname)
> +                    model, compat = output_dtb(fsw, seq, pathname,
> +                                               args.arch, args.compress)
> +                    entries.append([model, compat])
> +
> +    finish_fit(fsw, entries)
> +
> +    # Include the kernel itself in the returned file count
> +    return fsw.as_fdt().as_bytearray(), seq + 1, size
> +
> +
> +def run_make_fit():
> +    """Run the tool's main logic"""
> +    args = parse_args()
> +
> +    out_data, count, size = build_fit(args)
> +    with open(args.fit, 'wb') as outf:
> +        outf.write(out_data)
> +
> +    ext_fit_size = None
> +    if args.external:
> +        mkimage = os.environ.get('MKIMAGE', 'mkimage')

Do we need to add a 'mkimage' line in 
Documentation/process/changes.rst?

Kind regards,
Nicolas


> +        subprocess.check_call([mkimage, '-E', '-F', args.fit],
> +                              stdout=subprocess.DEVNULL)
> +
> +        with open(args.fit, 'rb') as inf:
> +            data = inf.read()
> +        ext_fit = libfdt.FdtRo(data)
> +        ext_fit_size = ext_fit.totalsize()
> +
> +    comp_size = len(out_data)
> +    print(f'FIT size {comp_size:#x}/{comp_size / 1024 / 1024:.1f} MB', end='')
> +    if ext_fit_size:
> +        print(f', header {ext_fit_size:#x}/{ext_fit_size / 1024:.1f} KB', end='')
> +    print(f', {count} files, uncompressed {size / 1024 / 1024:.1f} MB')
> +
> +
> +if __name__ == "__main__":
> +    sys.exit(run_make_fit())
> -- 
> 2.43.0.rc2.451.g8631bc7472-goog
>

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