1#!/usr/bin/env vpython3 2 3# Copyright 2021 The Chromium Authors 4# Use of this source code is governed by a BSD-style license that can be 5# found in the LICENSE file. 6 7# This is a wrapper script which runs a Cargo build.rs build script 8# executable in a Cargo-like environment. Build scripts can do arbitrary 9# things and we can't support everything. Moreover, we do not WANT 10# to support everything because that means the build is not deterministic. 11# Code review processes must be applied to ensure that the build script 12# depends upon only these inputs: 13# 14# * The environment variables set by Cargo here: 15# https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-build-scripts 16# * Output from rustc commands, e.g. to figure out the Rust version. 17# 18# Similarly, the only allowable output from such a build script 19# is currently: 20# 21# * Generated .rs files 22# * cargo:rustc-cfg output. 23# 24# That's it. We don't even support the other standard cargo:rustc- 25# output messages. 26 27import argparse 28import io 29import os 30import platform 31import re 32import subprocess 33import sys 34import tempfile 35 36# Set up path to be able to import action_helpers 37sys.path.append( 38 os.path.join(os.path.dirname(os.path.abspath(__file__)), os.pardir, 39 os.pardir, 'build')) 40import action_helpers 41 42 43RUSTC_VERSION_LINE = re.compile(r"(\w+): (.*)") 44 45 46def rustc_name(): 47 if platform.system() == 'Windows': 48 return "rustc.exe" 49 else: 50 return "rustc" 51 52 53def host_triple(rustc_path): 54 """ Works out the host rustc target. """ 55 args = [rustc_path, "-vV"] 56 known_vars = dict() 57 proc = subprocess.Popen(args, stdout=subprocess.PIPE) 58 for line in io.TextIOWrapper(proc.stdout, encoding="utf-8"): 59 m = RUSTC_VERSION_LINE.match(line.rstrip()) 60 if m: 61 known_vars[m.group(1)] = m.group(2) 62 return known_vars["host"] 63 64 65RUSTC_CFG_LINE = re.compile("cargo:rustc-cfg=(.*)") 66 67 68def main(): 69 parser = argparse.ArgumentParser(description='Run Rust build script.') 70 parser.add_argument('--build-script', 71 required=True, 72 help='build script to run') 73 parser.add_argument('--output', 74 required=True, 75 help='where to write output rustc flags') 76 parser.add_argument('--target', help='rust target triple') 77 parser.add_argument('--features', help='features', nargs='+') 78 parser.add_argument('--env', help='environment variable', nargs='+') 79 parser.add_argument('--rust-prefix', required=True, help='rust path prefix') 80 parser.add_argument('--generated-files', nargs='+', help='any generated file') 81 parser.add_argument('--out-dir', required=True, help='target out dir') 82 parser.add_argument('--src-dir', required=True, help='target source dir') 83 84 args = parser.parse_args() 85 86 rustc_path = os.path.join(args.rust_prefix, rustc_name()) 87 88 # We give the build script an OUT_DIR of a temporary directory, 89 # and copy out only any files which gn directives say that it 90 # should generate. Mostly this is to ensure we can atomically 91 # create those files, but it also serves to avoid side-effects 92 # from the build script. 93 # In the future, we could consider isolating this build script 94 # into a chroot jail or similar on some platforms, but ultimately 95 # we are always going to be reliant on code review to ensure the 96 # build script is deterministic and trustworthy, so this would 97 # really just be a backup to humans. 98 with tempfile.TemporaryDirectory() as tempdir: 99 env = {} # try to avoid build scripts depending on other things 100 env["RUSTC"] = os.path.abspath(rustc_path) 101 env["OUT_DIR"] = tempdir 102 env["CARGO_MANIFEST_DIR"] = os.path.abspath(args.src_dir) 103 env["HOST"] = host_triple(rustc_path) 104 if args.target is None: 105 env["TARGET"] = env["HOST"] 106 else: 107 env["TARGET"] = args.target 108 target_components = env["TARGET"].split("-") 109 if len(target_components) == 2: 110 env["CARGO_CFG_TARGET_ARCH"] = target_components[0] 111 env["CARGO_CFG_TARGET_VENDOR"] = '' 112 env["CARGO_CFG_TARGET_OS"] = target_components[1] 113 env["CARGO_CFG_TARGET_ENV"] = '' 114 elif len(target_components) == 3: 115 env["CARGO_CFG_TARGET_ARCH"] = target_components[0] 116 env["CARGO_CFG_TARGET_VENDOR"] = target_components[1] 117 env["CARGO_CFG_TARGET_OS"] = target_components[2] 118 env["CARGO_CFG_TARGET_ENV"] = '' 119 elif len(target_components) == 4: 120 env["CARGO_CFG_TARGET_ARCH"] = target_components[0] 121 env["CARGO_CFG_TARGET_VENDOR"] = target_components[1] 122 env["CARGO_CFG_TARGET_OS"] = target_components[2] 123 env["CARGO_CFG_TARGET_ENV"] = target_components[3] 124 else: 125 print(f'Invalid TARGET {env["TARGET"]}') 126 sys.exit(1) 127 # See https://crbug.com/325543500 for background. 128 # Cargo sets CARGO_CFG_TARGET_OS to "android" even when targeting *-androideabi. 129 if env["CARGO_CFG_TARGET_OS"].startswith("android"): 130 env["CARGO_CFG_TARGET_OS"] = "android" 131 elif env["CARGO_CFG_TARGET_OS"] == "darwin": 132 env["CARGO_CFG_TARGET_OS"] = "macos" 133 if args.features: 134 for f in args.features: 135 feature_name = f.upper().replace("-", "_") 136 env["CARGO_FEATURE_%s" % feature_name] = "1" 137 if args.env: 138 for e in args.env: 139 (k, v) = e.split("=") 140 env[k] = v 141 # Pass through a couple which are useful for diagnostics 142 if os.environ.get("RUST_BACKTRACE"): 143 env["RUST_BACKTRACE"] = os.environ.get("RUST_BACKTRACE") 144 if os.environ.get("RUST_LOG"): 145 env["RUST_LOG"] = os.environ.get("RUST_LOG") 146 147 # In the future we should, set all the variables listed here: 148 # https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-build-scripts 149 150 proc = subprocess.run([os.path.abspath(args.build_script)], 151 env=env, 152 cwd=args.src_dir, 153 encoding='utf8', 154 stdout=subprocess.PIPE, 155 stderr=subprocess.PIPE) 156 157 if proc.stderr.rstrip(): 158 print(proc.stderr.rstrip(), file=sys.stderr) 159 proc.check_returncode() 160 161 flags = "" 162 for line in proc.stdout.split("\n"): 163 m = RUSTC_CFG_LINE.match(line.rstrip()) 164 if m: 165 flags = "%s--cfg\n%s\n" % (flags, m.group(1)) 166 167 # AtomicOutput will ensure we only write to the file on disk if what we 168 # give to write() is different than what's currently on disk. 169 with action_helpers.atomic_output(args.output) as output: 170 output.write(flags.encode("utf-8")) 171 172 # Copy any generated code out of the temporary directory, 173 # atomically. 174 if args.generated_files: 175 for generated_file in args.generated_files: 176 in_path = os.path.join(tempdir, generated_file) 177 out_path = os.path.join(args.out_dir, generated_file) 178 out_dir = os.path.dirname(out_path) 179 if not os.path.exists(out_dir): 180 os.makedirs(out_dir) 181 with open(in_path, 'rb') as input: 182 with action_helpers.atomic_output(out_path) as output: 183 content = input.read() 184 output.write(content) 185 186 187if __name__ == '__main__': 188 sys.exit(main()) 189