Porting/Chromium/BE

Changes required to Chromium to work on big endian

• Skia

- Chromium assumes that the pixel format, when viewed as a 32-bit word, is either ARGB or ABGR. However, third_party/skia/include/core/SkImageInfo.h contains a check that the pixel format, when viewed as four 8-bit bytes, is either BGRA or RGBA. Hence either this check needs to be relaxed (Maybe it is bogus in the first place? The comments talk about "native ARGB 32-bit", yet the test goes out of its way to test the ordering as bytes and not as 32-bit words), or Chromium needs to learn about a different pixel format.

• Datapack
  • ui/base/resource/data_pack.cc

  - Need to byteswap metadata on input (resource file format is specified to use LE)

  • chrome/browser/themes/browser_theme_pack.cc

  - "datapack assumes little endian"

• Net
  • net/cert/crl_set.cc

  - "assumes little endian"

  • components/safe_browsing/db/v4_rice.cc

  - #error The code below assumes little-endianness.

• Media
  • media/ffmpeg/ffmpeg_common.cc and media/formats/mp4/box_definitions.cc

  - #error The code below assumes little-endianness.

  • media/renderers/paint_canvas_video_renderer.cc

  - Depending on choice of Skia pixel format, a new LIBYUV mapping set may be needed (see also third_party/libyuv below).

• I18N
  • base/i18n/icu_util.cc

  - Needs to use "icudtb.dat" instead of "icudtl.dat" on BE

• Sandbox
  • sandbox/linux/system_headers/linux_seccomp.h

  - The definition of the big endian variant is incorrect (contains a bogus "__AUDIO_ARCH_BE"). Also, it would be better to define two different macros AUDIT_ARCH_PPC64 and AUDIT_ARCH_PPC64LE (because that is how it actually looks in <linux/audit.h>), and choose the correct one in sandbox/linux/bpf_dsl/seccomp_macros.h instead.

• third_party/skia
  • include/private/GrTypesPriv.h

  - #error "Skia gpu currently assumes little endian"

  • src/opts/Sk4px_none.h

  - Sk4px::alphas, Sk4px::zeroAlphas, Sk4px::zeroColors: "This method assumes little-endian."

  • src/opts/SkXfermode_opts.h

  - a_rgb assumes specific component order

  • src/utils/SkJSON.cpp and src/utils/SkJSON.h

  - Tagged value implementation needs to be adapted for BE

• third_party/boringssl/src
  • crypto/fipsmodul/bn/bytes.c

  - Bignum I/O functions need adaption for BE

• third_party/blink
  • renderer/platform/graphics/gpu/webgl_image_conversion.cc

  - Does contain BE support, but a variable rename refactoring is missing from the BE code

  • renderer/platform/graphics/logging_canvas.cc

  - Does contain BE support, but a variable rename refactoring is missing from the BE code

  • renderer/platform/image-decoders/jpeg/jpeg_image_decoder.cc

  - #error Blink assumes a little-endian target.

  • renderer/platform/image-decoders/webp/webp_image_decoder.cc

  - #error Blink assumes a little-endian target.

  • renderer/platform/heap/asm/SaveRegisters_ppc64.S

  - Needs to handle ELF ABI v1

• third_party/perfetto
  • src/ipc/buffered_frame_deserializer.cc, src/ipc/buffered_frame_deserializer_unittest.cc

  - Uses "AssumeLittleEndian" template

  • src/protozero/message.cc

  - float and double handling need adjusting for BE (accoring to comment)

  • src/protozero/proto_decoder.cc

  - Byteswap implementations missing

• third_party/ffmpeg
  • chromium/scripts/build_ffmpeg.py

  - Needs to recognize 'ppc64' as well as 'ppc64le'

• third_party/webrtc
  • common_audio/wav_file.cc

  - WavReader::ReadSamples and WavWriter::WriteSamples need to byteswap the samples

  • common_audio/wav_header.cc

  - Conversion functions missing

• third_party/modp_b64
  • BUILD.gn

  - modp_b64 actually supports BE, but in converting to their own build system Google managed to lose the check to define WORDS_BIGENDIAN

  • modp_b64.cc

  - The prototype of modp_b64_decode needs to be updated to use size_t instead of int for the lengths, as it has been done for the LE variant

• third_party/libvpx

- The build system should move VSX-specific sources into a separate source set, and set the cflags "-maltivec -mvsx" for it. In the original build system the cflags were set based on a glob of the source filename, but in Googles build system it has to be done manually.

• third_party/libyuv

- Depending on choice of Skia pixel format, additional conversion function variants may be needed