2869b1349b
This fixes the display on Retina Macbooks. It also moves us away from depending on the ancient XCode3 sdk.
76 lines
4.4 KiB
Plaintext
76 lines
4.4 KiB
Plaintext
Deterministic OSX Dmg Notes.
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Working OSX DMG's are created in Linux by combining a recent clang,
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the Apple's binutils (ld, ar, etc), and DMG authoring tools.
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Apple uses clang extensively for development and has upstreamed the necessary
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functionality so that a vanilla clang can take advantage. It supports the use
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of -F, -target, -mmacosx-version-min, and --sysroot, which are all necessary
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when building for OSX. A pre-compiled version of 3.2 is used because it was not
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available in the Precise repositories at the time this work was started. In the
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future, it can be switched to use system packages instead.
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Apple's version of binutils (called cctools) contains lots of functionality
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missing in the FSF's binutils. In addition to extra linker options for
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frameworks and sysroots, several other tools are needed as well such as
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install_name_tool, lipo, and nmedit. These do not build under linux, so they
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have been patched to do so. The work here was used as a starting point:
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https://github.com/mingwandroid/toolchain4
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In order to build a working toolchain, the following source packages are needed
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from Apple: cctools, dyld, and ld64.
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Beware. This part is ugly. Very very very ugly. In the future, this should be
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broken out into a new repository and cleaned up. Additionally, the binaries
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only work when built as x86 and not x86_64. This is an especially nasty
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limitation because it must be linked with the toolchain's libLTO.so, meaning
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that the entire toolchain must be x86. Gitian x86_64 should not be used until
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this has been fixed, because it would mean that several native dependencies
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(openssl, libuuid, etc) would need to be built as x86 first.
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These tools inject timestamps by default, which produce non-deterministic
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binaries. The ZERO_AR_DATE environment variable is used to disable that.
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This version of cctools has been patched to use the current version of clang's
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headers and and its libLTO.so rather than those from llvmgcc, as it was
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originally done in toolchain4.
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To complicate things further, all builds must target an Apple SDK. These SDKs
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are free to download, but not redistributable.
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To obtain it, register for a developer account, then download xcode4630916281a.dmg:
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https://developer.apple.com/downloads/download.action?path=Developer_Tools/xcode_4.6.3/xcode4630916281a.dmg
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This file is several gigabytes in size, but only a single directory inside is
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needed: Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.7.sdk
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Unfortunately, the usual linux tools (7zip, hpmount, loopback mount) are incapable of opening this file.
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To create a tarball suitable for gitian input, mount the dmg in OSX, then create it with:
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$ tar -C /Volumes/Xcode/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/ -czf MacOSX10.7.sdk.tar.gz MacOSX10.7.sdk
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The gitian descriptors build 2 sets of files: Linux tools, then Apple binaries
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which are created using these tools. The build process has been designed to
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avoid including the SDK's files in Gitian's outputs. All interim tarballs are
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fully deterministic and may be freely redistributed.
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genisoimage is used to create the initial DMG. It is not deterministic as-is,
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so it has been patched. A system genisoimage will work fine, but it will not
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be deterministic because the file-order will change between invocations.
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The patch can be seen here:
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https://raw.githubusercontent.com/theuni/osx-cross-depends/master/patches/cdrtools/genisoimage.diff
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No effort was made to fix this cleanly, so it likely leaks memory badly. But
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it's only used for a single invocation, so that's no real concern.
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genisoimage cannot compress DMGs, so afterwards, the 'dmg' tool from the
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libdmg-hfsplus project is used to compress it. There are several bugs in this
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tool and its maintainer has seemingly abandoned the project. It has been forked
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and is available (with fixes) here: https://github.com/theuni/libdmg-hfsplus .
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The 'dmg' tool has the ability to create DMG's from scratch as well, but this
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functionality is broken. Only the compression feature is currently used.
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Ideally, the creation could be fixed and genisoimage would no longer be necessary.
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Background images and other features can be added to DMG files by inserting a
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.DS_Store before creation. The easiest way to create this file is to build a
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DMG without one, move it to a device running OSX, customize the layout, then
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grab the .DS_Store file for later use. That is the approach taken here.
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