A local copy of OpenSSL from GitHub
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  1. Notes for Android platforms
  2. ===========================
  3. Requirement details
  4. -------------------
  5. Beside basic tools like perl and make you'll need to download the Android
  6. NDK. It's available for Linux, macOS and Windows, but only Linux
  7. version was actually tested. There is no reason to believe that macOS
  8. wouldn't work. And as for Windows, it's unclear which "shell" would be
  9. suitable, MSYS2 might have best chances. NDK version should play lesser
  10. role, the goal is to support a range of most recent versions.
  11. Configuration
  12. -------------
  13. Android is a cross-compiled target and you can't rely on `./Configure`
  14. to find out the configuration target for you. You have to name your
  15. target explicitly; there are `android-arm`, `android-arm64`, `android-mips`,
  16. `android-mip64`, `android-x86` and `android-x86_64` (`*MIPS` targets are no
  17. longer supported with NDK R20+).
  18. Do not pass --cross-compile-prefix (as you might be tempted), as it
  19. will be "calculated" automatically based on chosen platform. However,
  20. you still need to know the prefix to extend your PATH, in order to
  21. invoke `$(CROSS_COMPILE)clang` [`*gcc` on NDK 19 and lower] and company.
  22. (`./Configure` will fail and give you a hint if you get it wrong.)
  23. Apart from `PATH` adjustment you need to set `ANDROID_NDK_ROOT` environment
  24. to point at the `NDK` directory. If you're using a side-by-side NDK the path
  25. will look something like `/some/where/android-sdk/ndk/<ver>`, and for a
  26. standalone NDK the path will be something like `/some/where/android-ndk-<ver>`.
  27. Both variables are significant at both configuration and compilation times.
  28. The NDK customarily supports multiple Android API levels, e.g. `android-14`,
  29. `android-21`, etc. By default latest API level is chosen. If you need to target
  30. an older platform pass the argument `-D__ANDROID_API__=N` to `Configure`,
  31. with `N` being the numerical value of the target platform version. For example,
  32. to compile for Android 10 arm64 with a side-by-side NDK r20.0.5594570
  33. export ANDROID_NDK_ROOT=/home/whoever/Android/android-sdk/ndk/20.0.5594570
  34. PATH=$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
  35. ./Configure android-arm64 -D__ANDROID_API__=29
  36. make
  37. Older versions of the NDK have GCC under their common prebuilt tools
  38. directory, so the bin path will be slightly different. EG: to compile
  39. for ICS on ARM with NDK 10d:
  40. export ANDROID_NDK_ROOT=/some/where/android-ndk-10d
  41. PATH=$ANDROID_NDK_ROOT/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin:$PATH
  42. ./Configure android-arm -D__ANDROID_API__=14
  43. make
  44. Caveat lector! Earlier OpenSSL versions relied on additional `CROSS_SYSROOT`
  45. variable set to `$ANDROID_NDK_ROOT/platforms/android-<api>/arch-<arch>` to
  46. appoint headers-n-libraries' location. It's still recognized in order
  47. to facilitate migration from older projects. However, since API level
  48. appears in `CROSS_SYSROOT` value, passing `-D__ANDROID_API__=N` can be in
  49. conflict, and mixing the two is therefore not supported. Migration to
  50. `CROSS_SYSROOT`-less setup is recommended.
  51. One can engage clang by adjusting PATH to cover same NDK's clang. Just
  52. keep in mind that if you miss it, Configure will try to use gcc...
  53. Also, PATH would need even further adjustment to cover unprefixed, yet
  54. target-specific, ar and ranlib. It's possible that you don't need to
  55. bother, if binutils-multiarch is installed on your Linux system.
  56. Another option is to create so called "standalone toolchain" tailored
  57. for single specific platform including Android API level, and assign its
  58. location to `ANDROID_NDK_ROOT`. In such case you have to pass matching
  59. target name to Configure and shouldn't use `-D__ANDROID_API__=N`. `PATH`
  60. adjustment becomes simpler, `$ANDROID_NDK_ROOT/bin:$PATH` suffices.
  61. Running tests (on Linux)
  62. ------------------------
  63. This is not actually supported. Notes are meant rather as inspiration.
  64. Even though build output targets alien system, it's possible to execute
  65. test suite on Linux system by employing qemu-user. The trick is static
  66. linking. Pass -static to Configure, then edit generated Makefile and
  67. remove occurrences of -ldl and -pie flags. You would also need to pick
  68. API version that comes with usable static libraries, 42/2=21 used to
  69. work. Once built, you should be able to
  70. env EXE_SHELL=qemu-<arch> make test
  71. If you need to pass additional flag to qemu, quotes are your friend, e.g.
  72. env EXE_SHELL="qemu-mips64el -cpu MIPS64R6-generic" make test