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Android is enabling support for the riscv64 ISA. Add a configuration option to support building for it, aligned with the existing linux-riscv64 configuration. Reviewed-by: Hugo Landau <hlandau@openssl.org> Reviewed-by: Todd Short <todd.short@me.com> (Merged from https://github.com/openssl/openssl/pull/23427)
91 lines
4.5 KiB
Markdown
91 lines
4.5 KiB
Markdown
Notes for Android platforms
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===========================
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Requirement details
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-------------------
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Beside basic tools like perl and make, you'll need to download the Android
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NDK. It's available for Linux, macOS and Windows, but only Linux
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version was actually tested. There is no reason to believe that macOS
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wouldn't work. And as for Windows, it's unclear which "shell" would be
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suitable, MSYS2 might have best chances. NDK version should play lesser
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role, the goal is to support a range of most recent versions.
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Configuration
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-------------
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Android is a cross-compiled target and you can't rely on `./Configure`
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to find out the configuration target for you. You have to name your
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target explicitly; there are `android-arm`, `android-arm64`, `android-mips`,
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`android-mip64`, `android-x86`, `android-x86_64` and `android-riscv64`
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(`*MIPS` targets are no longer supported with NDK R20+).
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Do not pass --cross-compile-prefix (as you might be tempted), as it
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will be "calculated" automatically based on chosen platform. However,
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you still need to know the prefix to extend your PATH, in order to
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invoke `$(CROSS_COMPILE)clang` [`*gcc` on NDK 19 and lower] and company.
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(`./Configure` will fail and give you a hint if you get it wrong.)
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Apart from `PATH` adjustment, you need to set `ANDROID_NDK_ROOT` environment
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to point at the `NDK` directory. If you're using a side-by-side NDK the path
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will look something like `/some/where/android-sdk/ndk/<ver>`, and for a
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standalone NDK the path will be something like `/some/where/android-ndk-<ver>`.
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Both variables are significant at both configuration and compilation times.
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The NDK customarily supports multiple Android API levels, e.g. `android-14`,
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`android-21`, etc. By default, latest API level is chosen. If you need to target
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an older platform pass the argument `-D__ANDROID_API__=N` to `Configure`,
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with `N` being the numerical value of the target platform version. For example,
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to compile for Android 10 arm64 with a side-by-side NDK r20.0.5594570
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export ANDROID_NDK_ROOT=/home/whoever/Android/android-sdk/ndk/20.0.5594570
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PATH=$ANDROID_NDK_ROOT/toolchains/llvm/prebuilt/linux-x86_64/bin:$ANDROID_NDK_ROOT/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin:$PATH
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./Configure android-arm64 -D__ANDROID_API__=29
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make
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Older versions of the NDK have GCC under their common prebuilt tools
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directory, so the bin path will be slightly different. EG: to compile
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for ICS on ARM with NDK 10d:
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export ANDROID_NDK_ROOT=/some/where/android-ndk-10d
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PATH=$ANDROID_NDK_ROOT/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin:$PATH
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./Configure android-arm -D__ANDROID_API__=14
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make
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Caveat lector! Earlier OpenSSL versions relied on additional `CROSS_SYSROOT`
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variable set to `$ANDROID_NDK_ROOT/platforms/android-<api>/arch-<arch>` to
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appoint headers-n-libraries' location. It's still recognized in order
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to facilitate migration from older projects. However, since API level
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appears in `CROSS_SYSROOT` value, passing `-D__ANDROID_API__=N` can be in
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conflict, and mixing the two is therefore not supported. Migration to
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`CROSS_SYSROOT`-less setup is recommended.
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One can engage clang by adjusting PATH to cover the same NDK's clang. Just
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keep in mind that if you miss it, Configure will try to use gcc...
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Also, PATH would need even further adjustment to cover unprefixed, yet
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target-specific, ar and ranlib. It's possible that you don't need to
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bother, if binutils-multiarch is installed on your Linux system.
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Another option is to create so called "standalone toolchain" tailored
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for single specific platform including Android API level, and assign its
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location to `ANDROID_NDK_ROOT`. In such case, you have to pass matching
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target name to Configure and shouldn't use `-D__ANDROID_API__=N`. `PATH`
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adjustment becomes simpler, `$ANDROID_NDK_ROOT/bin:$PATH` suffices.
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Running tests (on Linux)
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------------------------
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This is not actually supported. Notes are meant rather as inspiration.
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Even though build output targets alien system, it's possible to execute
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test suite on Linux system by employing qemu-user. The trick is static
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linking. Pass -static to Configure, then edit generated Makefile and
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remove occurrences of -ldl and -pie flags. You would also need to pick
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API version that comes with usable static libraries, 42/2=21 used to
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work. Once built, you should be able to
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env EXE_SHELL=qemu-<arch> make test
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If you need to pass additional flag to qemu, quotes are your friend, e.g.
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env EXE_SHELL="qemu-mips64el -cpu MIPS64R6-generic" make test
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