# Copyright (c) 2014 The Native Client Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# We use a special toolchain to build nacl_helper_bootstrap.  This
# seems a bit excessive for compiling one source file.  But it is
# the most reasonable way to instantiate the configs with different
# settings such as use_gold=false.  The minimal set of configs used
# for that file (see below) will sometimes try to use the switch
# -gsplit-dwarf under use_gold=true.  But without some other configs
# that add a -B option pointing at a custom-built binutils, on some
# builders (e.g. on older bots) Clang will fail with -gsplit-dwarf.
# Fortunately, -gsplit-dwarf is pointless for this build anyway
# since there is just one small file.  And we're not actually using
# Gold for the link, so use_gold=true is a false statement and might
# cause other problems.

here = get_label_info(".", "dir")
bootstrap_toolchain = here + "/toolchain:nacl_bootstrap_" + target_cpu
compiler = "g++"

if (default_toolchain == "//build/toolchain/cros:target") {
  import("//build/toolchain/cros_toolchain.gni")
  bootstrap_toolchain = "//build/toolchain/cros:nacl_bootstrap"
  compiler = cros_target_cxx
} else if (current_cpu == "arm" && !is_android) {
  compiler = "arm-linux-gnueabihf-g++"
} else if (current_cpu == "mipsel" && !is_android) {
  compiler = "mipsel-linux-gnu-g++"
}

if (current_toolchain == bootstrap_toolchain) {
  bootstrap_lib_path = "$target_out_dir/libnacl_bootstrap_lib.a"
  bootstrap_raw_path = "$target_out_dir/nacl_bootstrap_raw"
  bootstrap_exe_path = "$root_out_dir/nacl_helper_bootstrap"

  linker_script_path = rebase_path("nacl_bootstrap.x")

  if (current_cpu == "x64") {
    nacl_reserve_top = "0x0"
    linker_emulation = "elf_x86_64"
  }
  if (current_cpu == "x86") {
    nacl_reserve_top = "0x40000000"
    linker_emulation = "elf_i386"
  }
  if (current_cpu == "arm") {
    nacl_reserve_top = "0x40002000"
    linker_emulation = "armelf_linux_eabi"
  }
  if (current_cpu == "mipsel") {
    nacl_reserve_top = "0x40008000"
    linker_emulation = "elf32ltsmip"
  }

  static_library("nacl_bootstrap_lib") {
    # This code has very specific requirements related to its static
    # linking and minimal libc use.  It cannot support the normal variety
    # of build configs that the rest of the code is built with.  So it
    # resets the list of configs to empty, and then builds up from scratch
    # using only the basics that work here.
    configs = []
    configs += [
      "//build/config/compiler:compiler_cpu_abi",
      "//build/config/compiler:runtime_library",
      "//build/config/compiler:chromium_code",
      "//build/config/compiler:clang_revision",
      "//build/config/compiler:default_optimization",
      "//build/config/compiler:default_symbols",
    ]

    include_dirs = [ "//" ]

    cflags = [
      "-fno-builtin",

      # These might be the defaults in the compiler configuration,
      # but we want them all disabled for this build.
      "-fno-stack-protector",
      "-fno-pic",
      "-fno-PIC",
      "-fno-pie",
      "-fno-PIE",
    ]

    sources = [
      "nacl_bootstrap.c",
    ]

    deps = [
      "//build/config/nacl:nacl_base",
    ]
  }

  action("nacl_bootstrap_raw") {
    deps = [
      ":nacl_bootstrap_lib",
    ]
    script = "ld_bfd.py"

    sources = [
      bootstrap_lib_path,
      linker_script_path,
    ]
    outputs = [
      bootstrap_raw_path,
    ]
    args = [
      "--compiler",
      compiler,
      "-m",
      linker_emulation,
      "--build-id",

      # This program is (almost) entirely
      # standalone.  It has its own startup code, so
      # no crt1.o for it.  It is statically linked,
      # and on x86 it does not use libc at all.
      # However, on ARM it needs a few (safe) things
      # from libc.
      "-static",

      # On x86-64, the default page size with some linkers is 2M
      # rather than the real Linux page size of 4K.  And on ARM, the
      # default page size is 32K.  A larger page size is
      # incompatible with our custom linker script's special layout.
      # NOTE: It's important that this option come before --script!
      "-z",
      "max-page-size=0x1000",

      # Link with custom linker script for special
      # layout.  The script uses the symbol RESERVE_TOP.
      "--defsym",
      "RESERVE_TOP=" + nacl_reserve_top,
      "--script=" + rebase_path(linker_script_path, root_build_dir),
      "-o",
      rebase_path(bootstrap_raw_path, root_build_dir),

      "--whole-archive",
      rebase_path(bootstrap_lib_path, root_build_dir),
      "--no-whole-archive",
    ]
  }

  action("munge_nacl_helper_bootstrap") {
    deps = [
      ":nacl_bootstrap_raw",
    ]

    script = "nacl_bootstrap_munge_phdr.py"
    inputs = [
      bootstrap_raw_path,
    ]
    outputs = [
      bootstrap_exe_path,
    ]
    args = rebase_path(inputs + outputs, root_build_dir)
  }
} else if (is_linux) {
  copy("bootstrap") {
    bootstrap = ":munge_nacl_helper_bootstrap($bootstrap_toolchain)"

    bootstrap_out_dir = get_label_info(bootstrap, "root_out_dir")

    deps = [
      bootstrap,
    ]
    sources = [
      "$bootstrap_out_dir/nacl_helper_bootstrap",
    ]
    outputs = [
      "$root_out_dir/nacl_helper_bootstrap",
    ]
  }

  # Mark the compiler arg as used.
  compiler = compiler
}