core/build/def.bzl - monogon - Gitiles

 #  Copyright 2020 The Monogon Project Authors.
 #
 #  SPDX-License-Identifier: Apache-2.0
 #
 #  Licensed under the Apache License, Version 2.0 (the "License");
 #  you may not use this file except in compliance with the License.
 #  You may obtain a copy of the License at
 #
 #      http://www.apache.org/licenses/LICENSE-2.0
 #
 #  Unless required by applicable law or agreed to in writing, software
 #  distributed under the License is distributed on an "AS IS" BASIS,
 #  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 #  See the License for the specific language governing permissions and
 #  limitations under the License.

 def _build_pure_transition_impl(settings, attr):
     """
     Transition that enables pure, static build of Go binaries.
     """
     return {
         "@io_bazel_rules_go//go/config:pure": True,
         "@io_bazel_rules_go//go/config:static": True,
     }

 build_pure_transition = transition(
     implementation = _build_pure_transition_impl,
     inputs = [],
     outputs = [
         "@io_bazel_rules_go//go/config:pure",
         "@io_bazel_rules_go//go/config:static",
     ],
 )

 def _smalltown_initramfs_impl(ctx):
     """
     Generate an lz4-compressed initramfs based on a label/file list.
     """

     # Generate config file for gen_init_cpio that describes the initramfs to build.
     cpio_list_name = ctx.label.name + ".cpio_list"
     cpio_list = ctx.actions.declare_file(cpio_list_name)

     # Start out with some standard initramfs device files.
     cpio_list_content = [
         "dir /dev 0755 0 0",
         "nod /dev/console 0600 0 0 c 5 1",
         "nod /dev/null 0644 0 0 c 1 3",
         "nod /dev/kmsg 0644 0 0 c 1 11",
         "nod /dev/ptmx 0644 0 0 c 5 2",
     ]

     # Find all directories that need to be created.
     directories_needed = []
     for _, p in ctx.attr.files.items():
         if not p.startswith("/"):
             fail("file {} invalid: must begin with /".format(p))

         # Get all intermediate directories on path to file
         parts = p.split("/")[1:-1]
         directories_needed.append(parts)

     # Extend with extra directories defined by user.
     for p in ctx.attr.extra_dirs:
         if not p.startswith("/"):
             fail("directory {} invalid: must begin with /".format(p))

         parts = p.split("/")[1:]
         directories_needed.append(parts)

     directories = []
     for parts in directories_needed:
         # Turn directory parts [usr, local, bin] into successive subpaths [/usr, /usr/local, /usr/local/bin].
         last = ""
         for part in parts:
             last += "/" + part

             # TODO(q3k): this is slow - this should be a set instead, but starlark doesn't implement them.
             # For the amount of files we're dealing with this doesn't matter, but all stars are pointing towards this
             # becoming accidentally quadratic at some point in the future.
             if last not in directories:
                 directories.append(last)

     # Append instructions to create directories.
     # Serendipitously, the directories should already be in the right order due to us not using a set to create the
     # list. They might not be in an elegant order (ie, if files [/foo/one/one, /bar, /foo/two/two] are request, the
     # order will be [/foo, /foo/one, /bar, /foo/two]), but that's fine.
     for d in directories:
         cpio_list_content.append("dir {} 0755 0 0".format(d))

     # Append instructions to add files.
     inputs = []
     for label, p in ctx.attr.files.items():
         # Figure out if this is an executable.
         is_executable = True

         di = label[DefaultInfo]
         if di.files_to_run.executable == None:
             # Generated non-executable files will have DefaultInfo.files_to_run.executable == None
             is_executable = False
         elif di.files_to_run.executable.is_source:
             # Source files will have executable.is_source == True
             is_executable = False

         # Ensure only single output is declared.
         # If you hit this error, figure out a better logic to find what file you need, maybe looking at providers other
         # than DefaultInfo.
         files = di.files.to_list()
         if len(files) > 1:
             fail("file {} has more than one output: {}", p, files)
         src = files[0]
         inputs.append(src)

         mode = "0755" if is_executable else "0444"

         cpio_list_content.append("file {} {} {} 0 0".format(p, src.path, mode))

     # Write cpio_list.
     ctx.actions.write(cpio_list, "\n".join(cpio_list_content))

     gen_init_cpio = ctx.executable._gen_init_cpio
     savestdout = ctx.executable._savestdout
     lz4 = ctx.executable._lz4

     # Generate 'raw' (uncompressed) initramfs
     initramfs_raw_name = ctx.label.name
     initramfs_raw = ctx.actions.declare_file(initramfs_raw_name)
     ctx.actions.run(
         outputs = [initramfs_raw],
         inputs = [cpio_list] + inputs,
         tools = [savestdout, gen_init_cpio],
         executable = savestdout,
         arguments = [initramfs_raw.path, gen_init_cpio.path, cpio_list.path],
     )

     # Compress raw initramfs using lz4c.
     initramfs_name = ctx.label.name + ".lz4"
     initramfs = ctx.actions.declare_file(initramfs_name)
     ctx.actions.run(
         outputs = [initramfs],
         inputs = [initramfs_raw],
         tools = [savestdout, lz4],
         executable = lz4.path,
         arguments = ["-l", initramfs_raw.path, initramfs.path],
     )

     return [DefaultInfo(files = depset([initramfs]))]

 smalltown_initramfs = rule(
     implementation = _smalltown_initramfs_impl,
     doc = """
         Build a Smalltown initramfs. The initramfs will contain a basic /dev directory and all the files specified by the
         `files` attribute. Executable files will have their permissions set to 0755, non-executable files will have
         their permissions set to 0444. All parent directories will be created with 0755 permissions.
     """,
     attrs = {
         "files": attr.label_keyed_string_dict(
             mandatory = True,
             allow_files = True,
             doc = """
                 Dictionary of Labels to String, placing a given Label's output file in the initramfs at the location
                 specified by the String value. The specified labels must only have a single output.
             """,
             # Attach pure transition to ensure all binaries added to the initramfs are pure/static binaries.
             cfg = build_pure_transition,
         ),
         "extra_dirs": attr.string_list(
             default = [],
             doc = """
                 Extra directories to create. These will be created in addition to all the directories required to
                 contain the files specified in the `files` attribute.
             """,
         ),

         # Tools, implicit dependencies.
         "_gen_init_cpio": attr.label(
             default = Label("@linux//:gen_init_cpio"),
             executable = True,
             cfg = "host",
         ),
         "_lz4": attr.label(
             default = Label("@com_github_lz4_lz4//programs:lz4"),
             executable = True,
             cfg = "host",
         ),
         "_savestdout": attr.label(
             default = Label("//build/savestdout"),
             executable = True,
             cfg = "host",
         ),

         # Allow for transitions to be attached to this rule.
         "_whitelist_function_transition": attr.label(
             default = "@bazel_tools//tools/whitelists/function_transition_whitelist",
         ),
     },
 )
	# Copyright 2020 The Monogon Project Authors.
	#
	# SPDX-License-Identifier: Apache-2.0
	#
	# Licensed under the Apache License, Version 2.0 (the "License");
	# you may not use this file except in compliance with the License.
	# You may obtain a copy of the License at
	#
	# http://www.apache.org/licenses/LICENSE-2.0
	#
	# Unless required by applicable law or agreed to in writing, software
	# distributed under the License is distributed on an "AS IS" BASIS,
	# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	# See the License for the specific language governing permissions and
	# limitations under the License.

	def _build_pure_transition_impl(settings, attr):
	"""
	Transition that enables pure, static build of Go binaries.
	"""
	return {
	"@io_bazel_rules_go//go/config:pure": True,
	"@io_bazel_rules_go//go/config:static": True,
	}

	build_pure_transition = transition(
	implementation = _build_pure_transition_impl,
	inputs = [],
	outputs = [
	"@io_bazel_rules_go//go/config:pure",
	"@io_bazel_rules_go//go/config:static",
	],
	)

	def _smalltown_initramfs_impl(ctx):
	"""
	Generate an lz4-compressed initramfs based on a label/file list.
	"""

	# Generate config file for gen_init_cpio that describes the initramfs to build.
	cpio_list_name = ctx.label.name + ".cpio_list"
	cpio_list = ctx.actions.declare_file(cpio_list_name)

	# Start out with some standard initramfs device files.
	cpio_list_content = [
	"dir /dev 0755 0 0",
	"nod /dev/console 0600 0 0 c 5 1",
	"nod /dev/null 0644 0 0 c 1 3",
	"nod /dev/kmsg 0644 0 0 c 1 11",
	"nod /dev/ptmx 0644 0 0 c 5 2",
	]

	# Find all directories that need to be created.
	directories_needed = []
	for _, p in ctx.attr.files.items():
	if not p.startswith("/"):
	fail("file {} invalid: must begin with /".format(p))

	# Get all intermediate directories on path to file
	parts = p.split("/")[1:-1]
	directories_needed.append(parts)

	# Extend with extra directories defined by user.
	for p in ctx.attr.extra_dirs:
	if not p.startswith("/"):
	fail("directory {} invalid: must begin with /".format(p))

	parts = p.split("/")[1:]
	directories_needed.append(parts)

	directories = []
	for parts in directories_needed:
	# Turn directory parts [usr, local, bin] into successive subpaths [/usr, /usr/local, /usr/local/bin].
	last = ""
	for part in parts:
	last += "/" + part

	# TODO(q3k): this is slow - this should be a set instead, but starlark doesn't implement them.
	# For the amount of files we're dealing with this doesn't matter, but all stars are pointing towards this
	# becoming accidentally quadratic at some point in the future.
	if last not in directories:
	directories.append(last)

	# Append instructions to create directories.
	# Serendipitously, the directories should already be in the right order due to us not using a set to create the
	# list. They might not be in an elegant order (ie, if files [/foo/one/one, /bar, /foo/two/two] are request, the
	# order will be [/foo, /foo/one, /bar, /foo/two]), but that's fine.
	for d in directories:
	cpio_list_content.append("dir {} 0755 0 0".format(d))

	# Append instructions to add files.
	inputs = []
	for label, p in ctx.attr.files.items():
	# Figure out if this is an executable.
	is_executable = True

	di = label[DefaultInfo]
	if di.files_to_run.executable == None:
	# Generated non-executable files will have DefaultInfo.files_to_run.executable == None
	is_executable = False
	elif di.files_to_run.executable.is_source:
	# Source files will have executable.is_source == True
	is_executable = False

	# Ensure only single output is declared.
	# If you hit this error, figure out a better logic to find what file you need, maybe looking at providers other
	# than DefaultInfo.
	files = di.files.to_list()
	if len(files) > 1:
	fail("file {} has more than one output: {}", p, files)
	src = files[0]
	inputs.append(src)

	mode = "0755" if is_executable else "0444"

	cpio_list_content.append("file {} {} {} 0 0".format(p, src.path, mode))

	# Write cpio_list.
	ctx.actions.write(cpio_list, "\n".join(cpio_list_content))

	gen_init_cpio = ctx.executable._gen_init_cpio
	savestdout = ctx.executable._savestdout
	lz4 = ctx.executable._lz4

	# Generate 'raw' (uncompressed) initramfs
	initramfs_raw_name = ctx.label.name
	initramfs_raw = ctx.actions.declare_file(initramfs_raw_name)
	ctx.actions.run(
	outputs = [initramfs_raw],
	inputs = [cpio_list] + inputs,
	tools = [savestdout, gen_init_cpio],
	executable = savestdout,
	arguments = [initramfs_raw.path, gen_init_cpio.path, cpio_list.path],
	)

	# Compress raw initramfs using lz4c.
	initramfs_name = ctx.label.name + ".lz4"
	initramfs = ctx.actions.declare_file(initramfs_name)
	ctx.actions.run(
	outputs = [initramfs],
	inputs = [initramfs_raw],
	tools = [savestdout, lz4],
	executable = lz4.path,
	arguments = ["-l", initramfs_raw.path, initramfs.path],
	)

	return [DefaultInfo(files = depset([initramfs]))]

	smalltown_initramfs = rule(
	implementation = _smalltown_initramfs_impl,
	doc = """
	Build a Smalltown initramfs. The initramfs will contain a basic /dev directory and all the files specified by the
	`files` attribute. Executable files will have their permissions set to 0755, non-executable files will have
	their permissions set to 0444. All parent directories will be created with 0755 permissions.
	""",
	attrs = {
	"files": attr.label_keyed_string_dict(
	mandatory = True,
	allow_files = True,
	doc = """
	Dictionary of Labels to String, placing a given Label's output file in the initramfs at the location
	specified by the String value. The specified labels must only have a single output.
	""",
	# Attach pure transition to ensure all binaries added to the initramfs are pure/static binaries.
	cfg = build_pure_transition,
	),
	"extra_dirs": attr.string_list(
	default = [],
	doc = """
	Extra directories to create. These will be created in addition to all the directories required to
	contain the files specified in the `files` attribute.
	""",
	),

	# Tools, implicit dependencies.
	"_gen_init_cpio": attr.label(
	default = Label("@linux//:gen_init_cpio"),
	executable = True,
	cfg = "host",
	),
	"_lz4": attr.label(
	default = Label("@com_github_lz4_lz4//programs:lz4"),
	executable = True,
	cfg = "host",
	),
	"_savestdout": attr.label(
	default = Label("//build/savestdout"),
	executable = True,
	cfg = "host",
	),

	# Allow for transitions to be attached to this rule.
	"_whitelist_function_transition": attr.label(
	default = "@bazel_tools//tools/whitelists/function_transition_whitelist",
	),
	},
	)