This is a record of how I compile GCC 9.1 for ARM64 on Ubuntu 18.04.

Environment

1. Host Environment

host : Ubuntu 18.04
GCC version : 9.1.0(you may use defalut compiler of your Ubuntu)
Binutils version : 2.3
Glibc version : 2.27
Bison version : 3.0.4
Flex version : 2.6.4
GMP version : 6.1.2
MPC version : 1.1.0
MPFR version : 4.0.1
Texinfo version : 6.5.0
CLooG version : 0.18.4
ISL version : 0.19

2. Target

Source dir : /media/cliff/Work2/testKernel/src/
Target dir : $HOME/opt/cross
Gcc version : 9.1
Binutils version : 2.32
Linux kernel version : 5.0.1
Glibc version : 2.30

Step

1. Download Source

You can download source files from following sites.

Binutils : Binutils website, the GNU main mirror.

GCC : GCC website, the GNU main mirror.

Linux : Index of /pub/linux/kernel/

Glibc : Index of /gnu/glibc/

$ cd /media/cliff/Work2/testKernel/src/
$ ls 
    binutils-2.32   gcc-9.1   glibc-2.30    linux-5.0.1
$ touch asan_linux-cc.patch

Copy following code to the patch.

--- orig/asan_linux.cc    2019-07-11 21:18:56.000000000 +0100
+++ mod/asan_linux.cc	2019-07-11 16:31:42.000000000 +0100
@@ -75,6 +75,10 @@
 asan_rt_version_t  __asan_rt_version;
 }

+#ifndef PATH_MAX
+#define PATH_MAX 4096
+#endif
+
 namespace __asan {

 void InitializePlatformInterceptors() {}

$ patch -b gcc-9.1/libsanitizer/asan/asan_linux.cc asan_linux-cc.patch

You can find the backed up file as gcc-9.1/libsanitizer/asan/asan_linux.cc.orig

2. Set Environment Values

export PREFIX="$HOME/opt/cross"
export TARGET=aarch64-linux
export PATH="$PREFIX/bin:$PATH"

3. Build Binutils

cd /media/cliff/Work2/testKernel/src/
mkdir build-binutils
cd build-binutils
../binutils-2.32/configure --target=$TARGET --prefix=$PREFIX --with-sysroot --disable-multilib
make -j12
make install
cd ..

4. Linux Kernel Headers

cd linux-5.0.1
make ARCH=arm64 INSTALL_HDR_PATH=$PREFIX/$TARGET headers_install
cd ..

5. Build Gcc

mkdir -p build-gcc
cd build-gcc
../gcc-9.1/configure --prefix=$PREFIX --target=$TARGET --enable-languages=c,c++ --disable-multilib
make -j12 all-gcc
make install-gcc
cd ..

6. Build Glibc

mkdir -p build-glibc
cd build-glibc
../glibc-2.30/configure --prefix=$PREFIX/$TARGET --build=$MACHTYPE --host=aarch64-linux --target=aarch64-linux --with-headers=$PREFIX/$TARGET/include --disable-multilib libc_cv_forced_unwind=yes
make install-bootstrap-headers=yes install-headers
make -j12 csu/subdir_lib
install csu/crt1.o csu/crti.o csu/crtn.o $PREFIX/$TARGET/lib
aarch64-linux-gcc -nostdlib -nostartfiles -shared -x c /dev/null -o $PREFIX/$TARGET/lib/libc.so
touch $PREFIX/$TARGET/include/gnu/stubs.h
cd ..

7. Compiler Support Library

cd build-gcc
make -j12 all-target-libgcc
make install-target-libgcc
cd ..

8. Standard C Library

cd build-glibc
make -j12
make install
cd ..

9.Standard C++ Library

cd build-gcc
make -j12
make install
cd ..

Reference

[1] https://wiki.osdev.org/GCC_Cross-Compiler

[2] https://preshing.com/20141119/how-to-build-a-gcc-cross-compiler/

[3] http://docs.slackware.com/howtos:hardware:arm:gcc-9.x_aarch64_cross-compiler