fune/python/mozbuild/mozpack/executables.py

# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

from __future__ import absolute_import, print_function, unicode_literals

import os
import struct
import subprocess
from mozpack.errors import errors

MACHO_SIGNATURES = [
    0xFEEDFACE,  # mach-o 32-bits big endian
    0xCEFAEDFE,  # mach-o 32-bits little endian
    0xFEEDFACF,  # mach-o 64-bits big endian
    0xCFFAEDFE,  # mach-o 64-bits little endian
]

FAT_SIGNATURE = 0xCAFEBABE  # mach-o FAT binary

ELF_SIGNATURE = 0x7F454C46  # Elf binary

UNKNOWN = 0
MACHO = 1
ELF = 2


def get_type(path):
    """
    Check the signature of the give file and returns what kind of executable
    matches.
    """
    with open(path, "rb") as f:
        signature = f.read(4)
        if len(signature) < 4:
            return UNKNOWN
        signature = struct.unpack(">L", signature)[0]
        if signature == ELF_SIGNATURE:
            return ELF
        if signature in MACHO_SIGNATURES:
            return MACHO
        if signature != FAT_SIGNATURE:
            return UNKNOWN
        # We have to sanity check the second four bytes, because Java class
        # files use the same magic number as Mach-O fat binaries.
        # This logic is adapted from file(1), which says that Mach-O uses
        # these bytes to count the number of architectures within, while
        # Java uses it for a version number. Conveniently, there are only
        # 18 labelled Mach-O architectures, and Java's first released
        # class format used the version 43.0.
        num = f.read(4)
        if len(num) < 4:
            return UNKNOWN
        num = struct.unpack(">L", num)[0]
        if num < 20:
            return MACHO
        return UNKNOWN


def is_executable(path):
    """
    Return whether a given file path points to an executable or a library,
    where an executable or library is identified by:
        - the file extension on OS/2 and WINNT
        - the file signature on OS/X and ELF systems (GNU/Linux, Android, BSD,
          Solaris)

    As this function is intended for use to choose between the ExecutableFile
    and File classes in FileFinder, and choosing ExecutableFile only matters
    on OS/2, OS/X, ELF and WINNT (in GCC build) systems, we don't bother
    detecting other kind of executables.
    """
    from buildconfig import substs

    if not os.path.exists(path):
        return False

    if substs["OS_ARCH"] == "WINNT":
        return path.lower().endswith((substs["DLL_SUFFIX"], substs["BIN_SUFFIX"]))

    return get_type(path) != UNKNOWN


def may_strip(path):
    """
    Return whether strip() should be called
    """
    from buildconfig import substs

    # Bug 1658632: clang-11-based strip complains about d3dcompiler_47.dll.
    # It's not clear why this happens, but as a quick fix just avoid stripping
    # this DLL. It's not from our build anyway.
    if "d3dcompiler" in path:
        return False
    return bool(substs.get("PKG_STRIP"))


def strip(path):
    """
    Execute the STRIP command with STRIP_FLAGS on the given path.
    """
    from buildconfig import substs

    strip = substs["STRIP"]
    flags = substs.get("STRIP_FLAGS", [])
    cmd = [strip] + flags + [path]
    if subprocess.call(cmd) != 0:
        errors.fatal("Error executing " + " ".join(cmd))


def may_elfhack(path):
    """
    Return whether elfhack() should be called
    """
    # elfhack only supports libraries. We should check the ELF header for
    # the right flag, but checking the file extension works too.
    from buildconfig import substs

    return (
        "USE_ELF_HACK" in substs
        and substs["USE_ELF_HACK"]
        and path.endswith(substs["DLL_SUFFIX"])
        and "COMPILE_ENVIRONMENT" in substs
        and substs["COMPILE_ENVIRONMENT"]
    )


def elfhack(path):
    """
    Execute the elfhack command on the given path.
    """
    from buildconfig import topobjdir

    cmd = [os.path.join(topobjdir, "build/unix/elfhack/elfhack"), path]
    if subprocess.call(cmd) != 0:
        errors.fatal("Error executing " + " ".join(cmd))


def xz_compress(path):
    """
    Execute xz to compress the given path.
    """
    if open(path, "rb").read(5)[1:] == "7zXZ":
        print("%s is already compressed" % path)
        return

    from buildconfig import substs

    xz = substs.get("XZ")
    cmd = [xz, "-zkf", path]

    # For now, the mozglue XZStream ELF loader can only support xz files
    # with a single stream that contains a single block. In xz, there is no
    # explicit option to set the max block count. Instead, we force xz to use
    # single thread mode, which results in a single block.
    cmd.extend(["--threads=1"])

    bcj = None
    if substs.get("MOZ_THUMB2"):
        bcj = "--armthumb"
    elif substs.get("CPU_ARCH") == "arm":
        bcj = "--arm"
    elif substs.get("CPU_ARCH") == "x86":
        bcj = "--x86"

    if bcj:
        cmd.extend([bcj])

    # We need to explicitly specify the LZMA filter chain to ensure consistent builds
    # across platforms. Note that the dict size must be less then 16MiB per the hardcoded
    # value in mozglue/linker/XZStream.cpp. This is the default LZMA filter chain for for
    # xz-utils version 5.0. See:
    # https://github.com/xz-mirror/xz/blob/v5.0.0/src/liblzma/lzma/lzma_encoder_presets.c
    # https://github.com/xz-mirror/xz/blob/v5.0.0/src/liblzma/api/lzma/container.h#L31
    cmd.extend(["--lzma2=dict=8MiB,lc=3,lp=0,pb=2,mode=normal,nice=64,mf=bt4,depth=0"])
    print("xz-compressing %s with %s" % (path, " ".join(cmd)))

    if subprocess.call(cmd) != 0:
        errors.fatal("Error executing " + " ".join(cmd))
        return

    os.rename(path + ".xz", path)