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 env["CARGO_CFG_TARGET_ARCH"] = target_components[0] 110 if args.features: 111 for f in args.features: 112 feature_name = f.upper().replace("-", "_") 113 env["CARGO_FEATURE_%s" % feature_name] = "1" 114 if args.env: 115 for e in args.env: 116 (k, v) = e.split("=") 117 env[k] = v 118 # Pass through a couple which are useful for diagnostics 119 if os.environ.get("RUST_BACKTRACE"): 120 env["RUST_BACKTRACE"] = os.environ.get("RUST_BACKTRACE") 121 if os.environ.get("RUST_LOG"): 122 env["RUST_LOG"] = os.environ.get("RUST_LOG") 123 124 # In the future we should, set all the variables listed here: 125 # https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-build-scripts 126 127 proc = subprocess.run([os.path.abspath(args.build_script)], 128 env=env, 129 cwd=args.src_dir, 130 encoding='utf8', 131 capture_output=True) 132 133 if proc.stderr.rstrip(): 134 print(proc.stderr.rstrip(), file=sys.stderr) 135 proc.check_returncode() 136 137 flags = "" 138 for line in proc.stdout.split("\n"): 139 m = RUSTC_CFG_LINE.match(line.rstrip()) 140 if m: 141 flags = "%s--cfg\n%s\n" % (flags, m.group(1)) 142 143 # AtomicOutput will ensure we only write to the file on disk if what we 144 # give to write() is different than what's currently on disk. 145 with action_helpers.atomic_output(args.output) as output: 146 output.write(flags.encode("utf-8")) 147 148 # Copy any generated code out of the temporary directory, 149 # atomically. 150 if args.generated_files: 151 for generated_file in args.generated_files: 152 in_path = os.path.join(tempdir, generated_file) 153 out_path = os.path.join(args.out_dir, generated_file) 154 out_dir = os.path.dirname(out_path) 155 if not os.path.exists(out_dir): 156 os.makedirs(out_dir) 157 with open(in_path, 'rb') as input: 158 with action_helpers.atomic_output(out_path) as output: 159 content = input.read() 160 output.write(content) 161 162 163if __name__ == '__main__': 164 sys.exit(main()) 165