[Buildroot] [Patch v2 3/3] rust: new package

[Romain Naour <romain.naour@gmail.com>]

Hi Eric,

Le 24/06/2016 ? 21:46, Eric Le Bihan a ?crit :
> This new package provides the compiler for the Rust programming language.
> 
> Currently, only the host variant is built.
> 
> The internal build process is as follows:
> 
>  1. rustc-stage0, provided by rust-bootstrap, is used to build
>     rustc-stage1.
>  2. rust-stage1 builds the final Rust compiler (rust-stage2)
>     and the standard library for the host architecture.
>  3. the standard library for the target architecture is build.
> 
> The Rust compiler uses LLVM as its backend, compiled with support for
> x86, ARM, PowerPC and MIPS architectures.

rust build it's own bundled copy of llvm if it's not available on the host.
If host-rust require a llvm compiler we need to add llvm support in Buildroot first.

I have some WIP patches about llvm/clang, if you want to take a look:
https://github.com/RomainNaour/buildroot/tree/clang-llvm

Best regards,
Romain

> 
> To properly build the standard library for the target, two files are
> needed:
> 
>  - the target configuration: a Makefile fragment telling the build system
>    about the cross-compiler and such.
>  - the target specification: a JSON file describing the target
>    architecture to the LLVM backend.
> 
> These files are generated with a Python script which takes info from the
> Buildroot configuration: `rust-target-gen`.
> 
> When compiling Rust code with this compiler, the generated program only
> depends on the target C library, as it is statically linked to the Rust
> standard library.
> 
> Signed-off-by: Eric Le Bihan <eric.le.bihan.dev@free.fr>
> ---
>  package/Config.in.host                             |   1 +
>  ...monize-use-of-CROSS_PREFIX_-in-mk-cfg-.mk.patch |  53 ++++
>  .../0002-Expand-CC-to-gcc-in-x86-mk-cfg-.cfg.patch |  71 +++++
>  ...eclaration-in-mipsel-unknown-linux-gnu.mk.patch |  26 ++
>  package/rust/Config.in.host                        |   7 +
>  package/rust/rust-target-gen                       | 315 +++++++++++++++++++++
>  package/rust/rust.hash                             |   2 +
>  package/rust/rust.mk                               |  67 +++++
>  8 files changed, 542 insertions(+)
>  create mode 100644 package/rust/0001-Harmonize-use-of-CROSS_PREFIX_-in-mk-cfg-.mk.patch
>  create mode 100644 package/rust/0002-Expand-CC-to-gcc-in-x86-mk-cfg-.cfg.patch
>  create mode 100644 package/rust/0003-Fix-CPP-declaration-in-mipsel-unknown-linux-gnu.mk.patch
>  create mode 100644 package/rust/Config.in.host
>  create mode 100755 package/rust/rust-target-gen
>  create mode 100644 package/rust/rust.hash
>  create mode 100644 package/rust/rust.mk
> 
> diff --git a/package/Config.in.host b/package/Config.in.host
> index 04b7f19..5d3df08 100644
> --- a/package/Config.in.host
> +++ b/package/Config.in.host
> @@ -30,6 +30,7 @@ menu "Host utilities"
>  	source "package/patchelf/Config.in.host"
>  	source "package/pwgen/Config.in.host"
>  	source "package/qemu/Config.in.host"
> +	source "package/rust/Config.in.host"
>  	source "package/sam-ba/Config.in.host"
>  	source "package/squashfs/Config.in.host"
>  	source "package/sunxi-tools/Config.in.host"
> diff --git a/package/rust/0001-Harmonize-use-of-CROSS_PREFIX_-in-mk-cfg-.mk.patch b/package/rust/0001-Harmonize-use-of-CROSS_PREFIX_-in-mk-cfg-.mk.patch
> new file mode 100644
> index 0000000..6c09495
> --- /dev/null
> +++ b/package/rust/0001-Harmonize-use-of-CROSS_PREFIX_-in-mk-cfg-.mk.patch
> @@ -0,0 +1,53 @@
> +From 23d9dbfb3ad4a8d5d5997738e8b1436d076898e9 Mon Sep 17 00:00:00 2001
> +From: Eric Le Bihan <eric.le.bihan.dev@free.fr>
> +Date: Tue, 19 Apr 2016 10:49:20 +0200
> +Subject: [PATCH 1/3] Harmonize use of CROSS_PREFIX_* in mk/cfg/*.mk
> +
> +Use CROSS_PREFIX_ in Makefile fragments for cross-compiling on Linux
> +wherever possible.
> +
> +Signed-off-by: Eric Le Bihan <eric.le.bihan.dev@free.fr>
> +---
> + mk/cfg/mips-unknown-linux-gnu.mk   | 9 +++++----
> + mk/cfg/mipsel-unknown-linux-gnu.mk | 9 +++++----
> + 2 files changed, 10 insertions(+), 8 deletions(-)
> +
> +diff --git a/mk/cfg/mips-unknown-linux-gnu.mk b/mk/cfg/mips-unknown-linux-gnu.mk
> +index 65b0877..0fe95de 100644
> +--- a/mk/cfg/mips-unknown-linux-gnu.mk
> ++++ b/mk/cfg/mips-unknown-linux-gnu.mk
> +@@ -1,8 +1,9 @@
> + # mips-unknown-linux-gnu configuration
> +-CC_mips-unknown-linux-gnu=mips-linux-gnu-gcc
> +-CXX_mips-unknown-linux-gnu=mips-linux-gnu-g++
> +-CPP_mips-unknown-linux-gnu=mips-linux-gnu-gcc -E
> +-AR_mips-unknown-linux-gnu=mips-linux-gnu-ar
> ++CROSS_PREFIX_mips-unknown-linux-gnu=mips-linux-gnu-
> ++CC_mips-unknown-linux-gnu=gcc
> ++CXX_mips-unknown-linux-gnu=g++
> ++CPP_mips-unknown-linux-gnu=gcc -E
> ++AR_mips-unknown-linux-gnu=ar
> + CFG_LIB_NAME_mips-unknown-linux-gnu=lib$(1).so
> + CFG_STATIC_LIB_NAME_mips-unknown-linux-gnu=lib$(1).a
> + CFG_LIB_GLOB_mips-unknown-linux-gnu=lib$(1)-*.so
> +diff --git a/mk/cfg/mipsel-unknown-linux-gnu.mk b/mk/cfg/mipsel-unknown-linux-gnu.mk
> +index 4dadfc2..9340c46 100644
> +--- a/mk/cfg/mipsel-unknown-linux-gnu.mk
> ++++ b/mk/cfg/mipsel-unknown-linux-gnu.mk
> +@@ -1,8 +1,9 @@
> + # mipsel-unknown-linux-gnu configuration
> +-CC_mipsel-unknown-linux-gnu=mipsel-linux-gnu-gcc
> +-CXX_mipsel-unknown-linux-gnu=mipsel-linux-gnu-g++
> +-CPP_mipsel-unknown-linux-gnu=mipsel-linux-gnu-gcc
> +-AR_mipsel-unknown-linux-gnu=mipsel-linux-gnu-ar
> ++CROSS_PREFIX_mipsel-unknown-linux-gnu=mipsel-linux-gnu-
> ++CC_mipsel-unknown-linux-gnu=gcc
> ++CXX_mipsel-unknown-linux-gnu=g++
> ++CPP_mipsel-unknown-linux-gnu=gcc
> ++AR_mipsel-unknown-linux-gnu=ar
> + CFG_LIB_NAME_mipsel-unknown-linux-gnu=lib$(1).so
> + CFG_STATIC_LIB_NAME_mipsel-unknown-linux-gnu=lib$(1).a
> + CFG_LIB_GLOB_mipsel-unknown-linux-gnu=lib$(1)-*.so
> +--
> +2.1.4
> +
> diff --git a/package/rust/0002-Expand-CC-to-gcc-in-x86-mk-cfg-.cfg.patch b/package/rust/0002-Expand-CC-to-gcc-in-x86-mk-cfg-.cfg.patch
> new file mode 100644
> index 0000000..e473e18
> --- /dev/null
> +++ b/package/rust/0002-Expand-CC-to-gcc-in-x86-mk-cfg-.cfg.patch
> @@ -0,0 +1,71 @@
> +From a371eb06fef803dcf9894fa0ad6941341887d2d8 Mon Sep 17 00:00:00 2001
> +From: Eric Le Bihan <eric.le.bihan.dev@free.fr>
> +Date: Tue, 19 Apr 2016 12:51:29 +0200
> +Subject: [PATCH 2/3] Expand $(CC) to gcc in x86 mk/cfg/*.cfg
> +
> +Expand $(CC) and friends to gcc and introduce empty CROSS_PREFIX_ in
> +Makefile fragments for cross-compilation of i586, i686 and x86_64 Linux
> +platforms to allow use of Sourcery CodeBench toolchains.
> +---
> + mk/cfg/i586-unknown-linux-gnu.mk   | 9 +++++----
> + mk/cfg/i686-unknown-linux-gnu.mk   | 9 +++++----
> + mk/cfg/x86_64-unknown-linux-gnu.mk | 9 +++++----
> + 3 files changed, 15 insertions(+), 12 deletions(-)
> +
> +diff --git a/mk/cfg/i586-unknown-linux-gnu.mk b/mk/cfg/i586-unknown-linux-gnu.mk
> +index 0609f36..45af3b8 100644
> +--- a/mk/cfg/i586-unknown-linux-gnu.mk
> ++++ b/mk/cfg/i586-unknown-linux-gnu.mk
> +@@ -1,8 +1,9 @@
> + # i586-unknown-linux-gnu configuration
> +-CC_i586-unknown-linux-gnu=$(CC)
> +-CXX_i586-unknown-linux-gnu=$(CXX)
> +-CPP_i586-unknown-linux-gnu=$(CPP)
> +-AR_i586-unknown-linux-gnu=$(AR)
> ++CROSS_PREFIX_i686-unknown-linux-gnu=
> ++CC_i586-unknown-linux-gnu=gcc
> ++CXX_i586-unknown-linux-gnu=g++
> ++CPP_i586-unknown-linux-gnu=gcc -E
> ++AR_i586-unknown-linux-gnu=ar
> + CFG_LIB_NAME_i586-unknown-linux-gnu=lib$(1).so
> + CFG_STATIC_LIB_NAME_i586-unknown-linux-gnu=lib$(1).a
> + CFG_LIB_GLOB_i586-unknown-linux-gnu=lib$(1)-*.so
> +diff --git a/mk/cfg/i686-unknown-linux-gnu.mk b/mk/cfg/i686-unknown-linux-gnu.mk
> +index 88c0907..aa4ce42 100644
> +--- a/mk/cfg/i686-unknown-linux-gnu.mk
> ++++ b/mk/cfg/i686-unknown-linux-gnu.mk
> +@@ -1,8 +1,9 @@
> + # i686-unknown-linux-gnu configuration
> +-CC_i686-unknown-linux-gnu=$(CC)
> +-CXX_i686-unknown-linux-gnu=$(CXX)
> +-CPP_i686-unknown-linux-gnu=$(CPP)
> +-AR_i686-unknown-linux-gnu=$(AR)
> ++CROSS_PREFIX_i686-unknown-linux-gnu=
> ++CC_i686-unknown-linux-gnu=gcc
> ++CXX_i686-unknown-linux-gnu=g++
> ++CPP_i686-unknown-linux-gnu=gcc -E
> ++AR_i686-unknown-linux-gnu=ar
> + CFG_LIB_NAME_i686-unknown-linux-gnu=lib$(1).so
> + CFG_STATIC_LIB_NAME_i686-unknown-linux-gnu=lib$(1).a
> + CFG_LIB_GLOB_i686-unknown-linux-gnu=lib$(1)-*.so
> +diff --git a/mk/cfg/x86_64-unknown-linux-gnu.mk b/mk/cfg/x86_64-unknown-linux-gnu.mk
> +index 044c687..bdd88cd 100644
> +--- a/mk/cfg/x86_64-unknown-linux-gnu.mk
> ++++ b/mk/cfg/x86_64-unknown-linux-gnu.mk
> +@@ -1,8 +1,9 @@
> + # x86_64-unknown-linux-gnu configuration
> +-CC_x86_64-unknown-linux-gnu=$(CC)
> +-CXX_x86_64-unknown-linux-gnu=$(CXX)
> +-CPP_x86_64-unknown-linux-gnu=$(CPP)
> +-AR_x86_64-unknown-linux-gnu=$(AR)
> ++CROSS_PREFIX_x86_64-unknown-linux-gnu=
> ++CC_x86_64-unknown-linux-gnu=gcc
> ++CXX_x86_64-unknown-linux-gnu=g++
> ++CPP_x86_64-unknown-linux-gnu=gcc -E
> ++AR_x86_64-unknown-linux-gnu=ar
> + CFG_LIB_NAME_x86_64-unknown-linux-gnu=lib$(1).so
> + CFG_STATIC_LIB_NAME_x86_64-unknown-linux-gnu=lib$(1).a
> + CFG_LIB_GLOB_x86_64-unknown-linux-gnu=lib$(1)-*.so
> +--
> +2.1.4
> +
> diff --git a/package/rust/0003-Fix-CPP-declaration-in-mipsel-unknown-linux-gnu.mk.patch b/package/rust/0003-Fix-CPP-declaration-in-mipsel-unknown-linux-gnu.mk.patch
> new file mode 100644
> index 0000000..00d338f
> --- /dev/null
> +++ b/package/rust/0003-Fix-CPP-declaration-in-mipsel-unknown-linux-gnu.mk.patch
> @@ -0,0 +1,26 @@
> +From f6d8c8f6dcdbabead3a06ed8f592143afaad16ba Mon Sep 17 00:00:00 2001
> +From: Eric Le Bihan <eric.le.bihan.dev@free.fr>
> +Date: Tue, 19 Apr 2016 12:57:24 +0200
> +Subject: [PATCH 3/3] Fix CPP declaration in mipsel-unknown-linux-gnu.mk
> +
> +Signed-off-by: Eric Le Bihan <eric.le.bihan.dev@free.fr>
> +---
> + mk/cfg/mipsel-unknown-linux-gnu.mk | 2 +-
> + 1 file changed, 1 insertion(+), 1 deletion(-)
> +
> +diff --git a/mk/cfg/mipsel-unknown-linux-gnu.mk b/mk/cfg/mipsel-unknown-linux-gnu.mk
> +index 9340c46..aaa18c2 100644
> +--- a/mk/cfg/mipsel-unknown-linux-gnu.mk
> ++++ b/mk/cfg/mipsel-unknown-linux-gnu.mk
> +@@ -2,7 +2,7 @@
> + CROSS_PREFIX_mipsel-unknown-linux-gnu=mipsel-linux-gnu-
> + CC_mipsel-unknown-linux-gnu=gcc
> + CXX_mipsel-unknown-linux-gnu=g++
> +-CPP_mipsel-unknown-linux-gnu=gcc
> ++CPP_mipsel-unknown-linux-gnu=gcc -E
> + AR_mipsel-unknown-linux-gnu=ar
> + CFG_LIB_NAME_mipsel-unknown-linux-gnu=lib$(1).so
> + CFG_STATIC_LIB_NAME_mipsel-unknown-linux-gnu=lib$(1).a
> +--
> +2.1.4
> +
> diff --git a/package/rust/Config.in.host b/package/rust/Config.in.host
> new file mode 100644
> index 0000000..138e74e
> --- /dev/null
> +++ b/package/rust/Config.in.host
> @@ -0,0 +1,7 @@
> +config BR2_PACKAGE_HOST_RUST_ARCH_SUPPORTS
> +	bool
> +	default y
> +	depends on BR2_HOSTARCH = "x86_64" || BR2_HOSTARCH = "x86"
> +	depends on BR2_arm  || BR2_aarch64 || BR2_i386 \
> +		|| BR2_mips || BR2_mipsel  || BR2_x86_64
> +	depends on !BR2_ARM_CPU_ARMV4 && !BR2_ARM_CPU_ARMV5
> diff --git a/package/rust/rust-target-gen b/package/rust/rust-target-gen
> new file mode 100755
> index 0000000..b34b72a
> --- /dev/null
> +++ b/package/rust/rust-target-gen
> @@ -0,0 +1,315 @@
> +#!/usr/bin/env python2.7
> +# -*- coding: utf-8 -*-
> +#
> +# Copyright (C) 2016 Eric Le Bihan <eric.le.bihan.dev@free.fr>
> +#
> +# This program is free software: you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation, either version 2 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program. If not, see <http://www.gnu.org/licenses/>.
> +#
> +
> +"""
> +`rust-target-gen ` generates the target configuration or the specification
> +file for the Rust compiler.
> +
> +These files will be used when cross-compiling the standard library or any
> +program.
> +
> +The name of the target is to be formatted in one of the following schemes:
> +
> +- <cpu>-<vendor>-<os>-<system>
> +- <cpu>-<os>-<system>
> +
> +By default, the contents of the configuration file is generated and printed to
> +standard output. Add *-m spec* to the command line to generate the contents of
> +the specification file. Add *-o FILE* to write contents to file FILE.
> +
> +It is possible to explicitly set the type of CPU using the *--cpu* option. To
> +set one or more additional LLVM attributes (a.k.a. "features"), add as many as
> +*--feature* options as needed.
> +
> +"""
> +
> +import os
> +import re
> +import sys
> +import csv
> +import StringIO
> +import argparse
> +
> +__version__ = "0.1.1"
> +
> +
> +class GenerationError(Exception):
> +    """Error raised when generating file contents"""
> +
> +
> +class Target:
> +    """Store information about a target"""
> +    def __init__(self, name):
> +        match = re.match(r'([\w]+)(?:-([\w]+))?-linux-([\w]+)', name)
> +        if not match:
> +            raise ValueError("Invalid target name")
> +        self.cpu = match.group(1)
> +        self.vendor = match.group(2) or 'unknown'
> +        self.system = match.group(3)
> +        self.name = name
> +        self.prefix = name + "-"
> +
> +    def to_pattern(self):
> +        """Format the target name as search pattern"""
> +        if self.vendor == 'unknown':
> +            pattern = "{0.cpu}-[\w]+-linux-{0.system}"
> +        else:
> +            pattern = "{0.cpu}-(?!{0.vendor})[\w]+-linux-{0.system}"
> +        return pattern.format(self)
> +
> +    @property
> +    def canonical_name(self):
> +        """Return the canonical name of the target"""
> +        return "{0.cpu}-{0.vendor}-linux-{0.system}".format(self)
> +
> +
> +#: Default list of pre-link-args
> +DEFAULT_PRE_LINK_ARGS = ["-Wl,--as-needed", "-Wl,-z,noexecstack"]
> +
> +#: Template for the target specifiation JSON file
> +SPEC_TEMPLATE = """{{
> +      "llvm-target": "{name}",
> +      "target-endian": "{endianness}",
> +      "target-pointer-width": "{ptr-width}",
> +      "data-layout": "{data-layout}",
> +      "target-env": "{environment}",
> +      "target-vendor": "{vendor}",
> +      "arch": "{arch}",
> +      "os": "linux",
> +      "cpu": "{cpu}",
> +      "features": "{features}",
> +      "dynamic-linking": true,
> +      "executables": true,
> +      "morestack": true,
> +      "linker-is-gnu": true,
> +      "has-rpath": true,
> +      "pre-link-args": [
> +          {pre-link-args}
> +       ],
> +      "position-independent-executables": true,
> +      "archive-format": "gnu"
> +}}
> +"""
> +
> +#: Contents of the target specifiation database.
> +#: The information has been extracted from the Rust source code
> +#: (src/libbrust_back/target/*.rs) and formatted as CSV.
> +#: The first line is the header of the file, listing the fields of the table.
> +SPEC_DATABASE_CONTENTS = """name;arch;endianness;ptr-width;data-layout;cpu;features;pre-link-args
> +aarch64-unknown-linux-gnu;aarch64;little;64;e-m:e-i64:64-i128:128-n32:64-S128;;;;
> +arm-unknown-linux-gnueabihf;arm;little;32;e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64;;+v6,+vfp2;;
> +arm-unknown-linux-gnueabi;arm;little;32;e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64;;+v6;;
> +i586-unknown-linux-gnu;x86;little;32;e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128;pentium;;-m32
> +i686-unknown-linux-gnu;x86;little;32;e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128;pentium4;;-m32
> +mips-unknown-linux-gnu;mips;big;32;E-m:m-p:32:32-i8:8:32-i16:16:32-i64:64-n32-S64;;+mips32r2,+soft-float;;
> +mipsel-unknown-linux-gnu;mips;little;32;e-m:m-p:32:32-i8:8:32-i16:16:32-i64:64-n32-S64;;+mips32;;
> +x86_64-unknown-linux-gnu;x86_64;little;64;e-m:e-i64:64-f80:128-n8:16:32:64-S128;;;-m64
> +"""
> +
> +
> +def join_quoted(strings, delimiter=','):
> +    """Quote strings and join them as a single string, using a delimiter.
> +
> +    :param strings: list of strings
> +    :type strings: list
> +
> +    :param delimiter: optional delimiter
> +    :type delimiter: Optional[str]
> +
> +    :return: a new string
> +    :rtype: str
> +    """
> +    return delimiter.join(["\"{}\"".format(s) for s in strings])
> +
> +
> +def find_similar_spec(target):
> +    """Find a target specification similar to a given one.
> +
> +    :param target: target to be created
> +    :type target: Target
> +
> +    :return: the reference target specification as a dict
> +    :rtype: dict of str to str
> +    """
> +    expr = re.compile(target.to_pattern() + '$')
> +    f = StringIO.StringIO(SPEC_DATABASE_CONTENTS)
> +    reader = csv.DictReader(f, delimiter=';', quotechar='"')
> +    for row in reader:
> +        if expr.match(row['name']):
> +            spec = dict(row)
> +            fields = spec['name'].split('-')
> +            spec['vendor'] = fields[1]
> +            spec['environment'] = fields[3]
> +            pre_links_args = DEFAULT_PRE_LINK_ARGS + spec['pre-link-args'].split()
> +            spec['pre-link-args'] = join_quoted(pre_links_args, ', ')
> +            spec['cpu'] = spec['cpu'] or 'generic'
> +            return spec
> +
> +    raise GenerationError("Can not find matching specification")
> +
> +
> +def gen_spec(target, cpu=None, features=[]):
> +    """Generate target specification file.
> +
> +    :param target: target to be created
> +    :type target: Target
> +
> +    :param cpu: optional CPU type
> +    :type cpu: Optional[str]
> +
> +    :param features: optional list of additional LLVM features
> +    :type features: Optional[list]
> +
> +    :return: contents of the configuration file
> +    :rtype: str
> +    """
> +    spec = find_similar_spec(target)
> +    spec['name'] = target.name
> +    spec['vendor'] = target.vendor
> +    if features:
> +        spec['features'] += ',' + ','.join(features)
> +    spec['cpu'] = cpu or spec['cpu']
> +    return SPEC_TEMPLATE.format(**spec)
> +
> +
> +def gen_conf_from(target, filename):
> +    """Generate target configuration file from an existing one.
> +
> +    :param target: target to be created
> +    :type target: Target
> +
> +    :param filename: path to an existing configuration file
> +    :type str:
> +
> +    :return: contents of the new configuration file
> +    :rtype: str
> +    """
> +    (name, e) = os.path.splitext(os.path.basename(filename))
> +    expr = re.compile(r'CROSS_PREFIX_[-\w]+=(?:[-\w]+)?\n')
> +    with open(filename) as input:
> +        contents = input.read()
> +        contents = contents.replace(name, target.name)
> +        line = "CROSS_PREFIX_{}={}\n".format(target.name, target.prefix)
> +        if expr.search(contents):
> +            contents = expr.sub(line, contents)
> +        else:
> +            contents += line
> +
> +    return contents
> +
> +
> +def find_similar_conf(target, srcdir):
> +    """Find a configuration file similar to a given target.
> +
> +    :param target: target to be created
> +    :type target: Target
> +
> +    :param srcdir: path to Rust source code
> +    :type srcdir: str
> +
> +    :return: path to the matching configuration file
> +    :rtype: str
> +    """
> +    cfgdir = os.path.join(srcdir, 'mk', 'cfg')
> +    expr = re.compile(target.to_pattern() + '.mk')
> +    candidates = filter(lambda f: expr.match(f), os.listdir(cfgdir))
> +    if len(candidates) != 1:
> +        raise GenerationError("Can not find matching configuration")
> +    return os.path.join(cfgdir, candidates[0])
> +
> +
> +def gen_conf(target, srcdir):
> +    """Generate target configuration file.
> +
> +    :param target: target to be created
> +    :type target: Target
> +
> +    :param srcdir: path to Rust source code
> +    :type srcdir: str
> +
> +    :return: contents of the configuration file
> +    :rtype: str
> +    """
> +    reference = find_similar_conf(target, srcdir)
> +    return gen_conf_from(target, reference)
> +
> +
> +def save_to_file(filename, text):
> +    """Save text to a file.
> +
> +    :param filename: path to the destination filename
> +    :type filename: str
> +
> +    :param text: contents of the file
> +    :type text: str
> +    """
> +    dstdir = os.path.dirname(filename)
> +    if not os.path.exists(dstdir):
> +        os.makedirs(dstdir)
> +    with open(filename, 'w') as f:
> +        f.write(contents)
> +
> +
> +if __name__ == '__main__':
> +    parser = argparse.ArgumentParser()
> +    parser.add_argument('-v', '--version',
> +                        action='version',
> +                        version=__version__)
> +    parser.add_argument('-c', '--cpu',
> +                        help='Set CPU type')
> +    parser.add_argument('-f', '--feature',
> +                        action='append',
> +                        metavar='FEATURE',
> +                        dest='features',
> +                        default=[],
> +                        help='Add new LLVM feature')
> +    parser.add_argument('-i', '--input',
> +                        dest='srcdir',
> +                        metavar='DIR',
> +                        default=os.getcwd(),
> +                        help='set the path to Rust source code')
> +    parser.add_argument('-p', '--prefix',
> +                        help='set the cross-compiler prefix')
> +    parser.add_argument('-m', '--mode',
> +                        choices=('conf', 'spec'),
> +                        default='conf',
> +                        help='set the operating mode')
> +    parser.add_argument('-o', '--output',
> +                        metavar='FILE',
> +                        help='write generated contents to FILE')
> +    parser.add_argument('target',
> +                        help='target name ("<cpu>-<vendor>-<os>-<system>")')
> +
> +    args = parser.parse_args()
> +
> +    target = Target(args.target)
> +    if args.prefix:
> +        target.prefix = args.prefix
> +
> +    if args.mode == 'conf':
> +        contents = gen_conf(target, args.srcdir)
> +    else:
> +        contents = gen_spec(target, args.cpu, args.features)
> +
> +    if not args.output:
> +        sys.stdout.write(contents)
> +    else:
> +        save_to_file(args.output, contents)
> +
> +# vim: ts=4 sw=4 sts=4 et ai
> diff --git a/package/rust/rust.hash b/package/rust/rust.hash
> new file mode 100644
> index 0000000..da2006b
> --- /dev/null
> +++ b/package/rust/rust.hash
> @@ -0,0 +1,2 @@
> +# Locally calculated
> +sha256 b19b21193d7d36039debeaaa1f61cbf98787e0ce94bd85c5cbe2a59462d7cfcd rustc-1.9.0-src.tar.gz
> diff --git a/package/rust/rust.mk b/package/rust/rust.mk
> new file mode 100644
> index 0000000..adb980a
> --- /dev/null
> +++ b/package/rust/rust.mk
> @@ -0,0 +1,67 @@
> +################################################################################
> +#
> +# rust
> +#
> +################################################################################
> +
> +RUST_VERSION = 1.9.0
> +RUST_SOURCE = rustc-$(RUST_VERSION)-src.tar.gz
> +RUST_SITE = https://static.rust-lang.org/dist
> +RUST_LICENSE = Apache-2.0, MIT
> +RUST_LICENSE_FILES = LICENSE-APACHE LICENSE-MIT
> +
> +HOST_RUST_DEPENDENCIES = host-rust-bootstrap host-python toolchain host-jemalloc
> +
> +define HOST_RUST_GEN_CONF
> +	package/rust/rust-target-gen \
> +		--mode conf \
> +		--prefix=$(notdir $(TARGET_CROSS)) \
> +		--input $(@D) \
> +		--output $(@D)/mk/cfg/$(GNU_TARGET_NAME).mk \
> +		$(GNU_TARGET_NAME)
> +endef
> +
> +define HOST_RUST_GEN_SPEC
> +	package/rust/rust-target-gen \
> +		--mode spec \
> +		--input $(@D) \
> +		--output $(HOST_DIR)/etc/rustc/$(GNU_TARGET_NAME).json \
> +		$(GNU_TARGET_NAME)
> +endef
> +
> +HOST_RUST_PRE_CONFIGURE_HOOKS += \
> +	HOST_RUST_GEN_CONF \
> +	HOST_RUST_GEN_SPEC
> +
> +HOST_RUST_MAKE_ENV = RUST_TARGET_PATH=$(HOST_DIR)/etc/rustc
> +HOST_RUST_MAKE_OPTS = $(if $(VERBOSE),VERBOSE=1)
> +
> +# Though not using autotools, Rust follows the ./configure convention, in its
> +# own way...
> +define HOST_RUST_CONFIGURE_CMDS
> +	(cd $(@D); $(HOST_CONFIGURE_OPTS) \
> +		./configure \
> +		--target=$(GNU_TARGET_NAME) \
> +		--prefix="$(HOST_DIR)/usr" \
> +		--jemalloc-root="$(HOST_DIR)/usr/lib" \
> +		--enable-local-rust \
> +		--local-rust-root="$(HOST_RUST_BOOTSTRAP_DIR)" \
> +		--disable-docs \
> +		--disable-manage-submodules \
> +		--sysconfdir="$(HOST_DIR)/etc" \
> +		--localstatedir="$(HOST_DIR)/var/lib" \
> +		--datadir="$(HOST_DIR)/usr/share" \
> +		--infodir="$(HOST_DIR)/usr/share/info")
> +endef
> +
> +define HOST_RUST_BUILD_CMDS
> +	$(HOST_MAKE_ENV) $(HOST_RUST_MAKE_ENV) $(MAKE) \
> +		$(HOST_RUST_MAKE_OPTS) -C $(@D)
> +endef
> +
> +define HOST_RUST_INSTALL_CMDS
> +	$(HOST_MAKE_ENV) $(HOST_RUST_MAKE_ENV) $(MAKE) \
> +		$(HOST_RUST_MAKE_OPTS) -C $(@D) install
> +endef
> +
> +$(eval $(host-generic-package))
>