treewide: Support aarch64-android using minimal prebuilt components

This PR adds a new aarch64 android toolchain, which leverages the
existing crossSystem infrastructure and LLVM builders to generate a
working toolchain with minimal prebuilt components.

The only thing that is prebuilt is the bionic libc. This is because it
is practically impossible to compile bionic outside of an AOSP tree. I
tried and failed, braver souls may prevail. For now I just grab the
relevant binaries from https://android.googlesource.com/.

I also grab the msm kernel sources from there to generate headers. I've
included a minor patch to the existing kernel-headers derivation in
order to expose an internal function.

Everything else, from binutils up, is using stock code. Many thanks to
@Ericson2314 for his help on this, and for building such a powerful
system in the first place!

One motivation for this is to be able to build a toolchain which will
work on an aarch64 linux machine. To my knowledge, there is no existing
toolchain for an aarch64-linux builder and an aarch64-android target.

2 files changed, 155 insertions, 0 deletions

diff --git a/pkgs/os-specific/linux/bionic-prebuilt/default.nix b/pkgs/os-specific/linux/bionic-prebuilt/default.nix
new file mode 100644
index 00000000000..4536067cbf3
--- /dev/null
+++ b/pkgs/os-specific/linux/bionic-prebuilt/default.nix
@@ -0,0 +1,113 @@
+{ stdenvNoCC, lib, fetchurl, fetchzip, pkgs
+}:
+let
+
+  prebuilt_crt = fetchzip {
+    url =  "https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9/+archive/98dce673ad97a9640c5d90bbb1c718e75c21e071/lib/gcc/aarch64-linux-android/4.9.x.tar.gz";
+    sha256 = "sha256-LLD2OJi78sNN5NulOsJZl7Ei4F1EUYItGG6eUsKWULc=";
+    stripRoot = false;
+  };
+
+  prebuilt_libs = fetchzip {
+    url = "https://android.googlesource.com/platform/prebuilts/ndk/+archive/f2c77d8ba8a7f5c2d91771e31164f29be0b8ff98/platform/platforms/android-30/arch-arm64/usr/lib.tar.gz";
+    sha256 = "sha256-TZBV7+D1QvKOCEi+VNGT5SStkgj0xRbyWoLH65zSrjw=";
+    stripRoot = false;
+  };
+
+  prebuilt_ndk_crt = fetchzip {
+    url = "https://android.googlesource.com/toolchain/prebuilts/ndk/r23/+archive/6c5fa4c0d3999b9ee932f6acbd430eb2f31f3151/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/aarch64-linux-android/30.tar.gz";
+    sha256 = "sha256-KHw+cCwAwlm+5Nwp1o8WONqdi4BBDhFaVVr+7GxQ5uE=";
+    stripRoot = false;
+  };
+
+  ndk_support_headers = fetchzip {
+    url ="https://android.googlesource.com/platform/prebuilts/clang/host/linux-x86/+archive/0e7f808fa26cce046f444c9616d9167dafbfb272/clang-r416183b/include/c++/v1/support.tar.gz";
+    sha256 = "sha256-NBv7Pk1CEaz8ns9moleEERr3x/rFmVmG33LgFSeO6fY=";
+    stripRoot = false;
+  };
+
+  kernelHeaders = pkgs.makeLinuxHeaders {
+    version = "android-common-11-5.4";
+    src = fetchurl {
+      url = "https://android.googlesource.com/kernel/common/+archive/48ffcbf0b9e7f0280bfb8c32c68da0aaf0fdfef6.tar.gz";
+      sha256 = "0ksm1243zm9hsv0a6q9v15jabf2rivsn14kmnm2qw6zk3mjd4jvv";
+    };
+  };
+
+in
+stdenvNoCC.mkDerivation rec {
+  pname = "bionic-prebuilt";
+  version = "ndk-release-r23";
+
+  src = fetchurl {
+    url = "https://android.googlesource.com/platform/bionic/+archive/00e8ce1142d8823b0d2fc8a98b40119b0f1f02cd.tar.gz";
+    sha256 = "0cfkwdcb2c9nnlmkx0inbsja3cyiha71nj92lm66m5an70zc3b8q";
+  };
+
+  sourceRoot = ".";
+
+  NIX_DONT_SET_RPATH = true;
+
+  dontConfigure = true;
+  dontBuild = true;
+
+  patches = [
+    ./ndk-version.patch
+  ];
+
+  postPatch = ''
+    substituteInPlace libc/include/sys/cdefs.h --replace \
+      "__has_builtin(__builtin_umul_overflow)" "1"
+    substituteInPlace libc/include/bits/ioctl.h --replace \
+      "!defined(BIONIC_IOCTL_NO_SIGNEDNESS_OVERLOAD)" "0"
+  '';
+
+  installPhase= ''
+    # copy the bionic headers
+    mkdir -p $out/include/support $out/include/android
+    cp -vr libc/include/* $out/include
+    # copy the kernel headers
+    cp -vr ${kernelHeaders}/include/*  $out/include/
+
+    chmod -R +w $out/include/linux
+
+    # fix a bunch of kernel headers so that things can actually be found
+    sed -i 's,struct epoll_event {,#include <bits/epoll_event.h>\nstruct Xepoll_event {,' $out/include/linux/eventpoll.h
+    sed -i 's,struct in_addr {,typedef unsigned int in_addr_t;\nstruct in_addr {,' $out/include/linux/in.h
+    sed -i 's,struct udphdr {,struct Xudphdr {,' $out/include/linux/udp.h
+    sed -i 's,union semun {,union Xsemun {,' $out/include/linux/sem.h
+    sed -i 's,struct __kernel_sockaddr_storage,#define sockaddr_storage __kernel_sockaddr_storage\nstruct __kernel_sockaddr_storage,' $out/include/linux/socket.h
+    sed -i 's,#ifndef __UAPI_DEF_.*$,#if 1,' $out/include/linux/libc-compat.h
+    substituteInPlace $out/include/linux/in.h --replace "__be32		imr_" "struct in_addr		imr_"
+    substituteInPlace $out/include/linux/in.h --replace "__be32		imsf_" "struct in_addr		imsf_"
+    substituteInPlace $out/include/linux/sysctl.h --replace "__unused" "_unused"
+
+    # what could possibly live in <linux/compiler.h>
+    touch $out/include/linux/compiler.h
+
+    # copy the support headers
+    cp -vr ${ndk_support_headers}* $out/include/support/
+
+    mkdir $out/lib
+    cp -v ${prebuilt_crt.out}/*.o $out/lib/
+    cp -v ${prebuilt_crt.out}/libgcc.a $out/lib/
+    cp -v ${prebuilt_ndk_crt.out}/*.o $out/lib/
+    for i in libc.so libm.so libdl.so liblog.so; do
+      cp -v ${prebuilt_libs.out}/$i $out/lib/
+    done
+
+    mkdir -p $dev/include
+    cp -v $out/include/*.h $dev/include/
+  '';
+
+  outputs = [ "out" "dev" ];
+  passthru.linuxHeaders = kernelHeaders;
+
+  meta = with lib; {
+    description = "The Android libc implementation";
+    homepage    = "https://android.googlesource.com/platform/bionic/";
+    license     = licenses.mit;
+    platforms   = platforms.linux;
+    maintainers = with maintainers; [ s1341 ];
+  };
+}
diff --git a/pkgs/os-specific/linux/bionic-prebuilt/ndk-version.patch b/pkgs/os-specific/linux/bionic-prebuilt/ndk-version.patch
new file mode 100644
index 00000000000..a6842ed479f
--- /dev/null
+++ b/pkgs/os-specific/linux/bionic-prebuilt/ndk-version.patch
@@ -0,0 +1,42 @@
+--- a/libc/include/android/ndk-version.h	2021-04-01 16:08:03.109183965 +0300
++++ b/libc/include/android/ndk-version.h	2021-04-01 16:07:19.811424641 +0300
+@@ -0,0 +1,39 @@
++#pragma once
++
++/**
++ * Set to 1 if this is an NDK, unset otherwise. See
++ * https://android.googlesource.com/platform/bionic/+/master/docs/defines.md.
++ */
++#define __ANDROID_NDK__ 1
++
++/**
++ * Major version of this NDK.
++ *
++ * For example: 16 for r16.
++ */
++#define __NDK_MAJOR__ 22
++
++/**
++ * Minor version of this NDK.
++ *
++ * For example: 0 for r16 and 1 for r16b.
++ */
++#define __NDK_MINOR__ 0
++
++/**
++ * Set to 0 if this is a release build, or 1 for beta 1,
++ * 2 for beta 2, and so on.
++ */
++#define __NDK_BETA__ 0
++
++/**
++ * Build number for this NDK.
++ *
++ * For a local development build of the NDK, this is -1.
++ */
++#define __NDK_BUILD__ 7026061
++
++/**
++ * Set to 1 if this is a canary build, 0 if not.
++ */
++#define __NDK_CANARY__ 0