Decent multiarch with make O=

run

@@ -3,41 +3,39 @@ set -e
 arch='x86_64'
 while getopts a: OPT > /dev/null 2>&1; do
   case "$OPT" in
-    a)
+    'a')
       arch=$OPTARG
       ;;
   esac
 done
 case "$arch" in
-  x86_64)
+  'x86_64')
     defconfig=qemu_x86_64_defconfig
     ;;
-  arm)
+  'arm')
     # qemu_arm_vexpress_defconfig required a newer QEMU than 2.0.0 on a Ubuntu host.
     # so let's stick to versatile for now.
     defconfig=qemu_arm_versatile_defconfig
     ;;
 esac
 
-./setoutarch "$arch"
 cd buildroot
 for p in $(find '../buildroot_patches/' -maxdepth 1 -name '*.patch' -print); do
     patch -N -r - -p 1 <"$p" || :
 done
-make BR2_EXTERNAL="$(pwd)/../kernel_module" "$defconfig"
+outdir="output.${arch}~"
+make O="$outdir" BR2_EXTERNAL="$(pwd)/../kernel_module" "$defconfig"
 # TODO Can't get rid of this for now.
 # http://stackoverflow.com/questions/44078245/is-it-possible-to-use-config-fragments-with-buildroots-config
-cat ../buildroot_config_fragment >> .config
+cat ../buildroot_config_fragment >> "${outdir}/.config"
 # HOST_QEMU_OPTS is a hack that happens to work because the QEMU package luckly uses += at all times.
 # It shouldn't be necessary in the first place: https://bugs.busybox.net/show_bug.cgi?id=9936
 # Even if were an autotools package, there is no general way currently to pass extra configs to it:
 # https://stackoverflow.com/questions/44341188/how-to-pass-extra-custom-configure-autotools-options-to-a-buildroot-package/44341225#44341225
-#
-# We might add this later on.
-# host-qemu-rebuild \
 env \
   -u LD_LIBRARY_PATH \
   make \
+  O="$outdir" \
   BR2_JLEVEL="$(($(nproc) - 2))" \
   HOST_QEMU_OPTS="--enable-debug --enable-sdl --with-sdlabi=2.0" \
   host-qemu-rebuild \

rungdb

@@ -21,9 +21,10 @@ else
   brk=""
 fi
 
-gdb="$(pwd)/buildroot/output/host/usr/bin/${arch}-linux-gdb"
-cd buildroot/output/build/linux-?.*.*/
-if $kgdb; then
+buildroot_out_dir="$(pwd)/buildroot/output.${arch}~"
+gdb="${buildroot_out_dir}/host/usr/bin/${arch}-linux-gdb"
+cd "${buildroot_out_dir}/build"/linux-?.*.*/
+if "$kgdb"; then
     cmd="$gdb \
       -q \
       -ex 'add-auto-load-safe-path $(pwd)' \
@@ -32,7 +33,7 @@ if $kgdb; then
     "
 else
   case "$arch" in
-    x86_64)
+    'x86_64')
       # http://stackoverflow.com/questions/11408041/how-to-debug-the-linux-kernel-with-gdb-and-qemu/33203642#33203642
       # http://stackoverflow.com/questions/4943857/linux-kernel-live-debugging-how-its-done-and-what-tools-are-used/42316607#42316607
       # http://stackoverflow.com/questions/28607538/how-to-debug-linux-kernel-modules-with-qemu/44095831#44095831
@@ -50,7 +51,7 @@ else
         -ex 'lx-symbols ../kernel_module-1.0/'
       "
       ;;
-    arm)
+    'arm')
       cmd="$gdb \
         -q \
         -ex 'add-auto-load-safe-path $(pwd)' \

runqemu

@@ -43,8 +43,7 @@ done
 shift "$(($OPTIND - 1))"
 extra_flags="$extra_flags $@"
 
-./setoutarch "$arch"
-buildroot_out_dir='./buildroot/output'
+buildroot_out_dir="./buildroot/output.${arch}~"
 images_dir="$buildroot_out_dir/images"
 qemu_common="\
 $debug_qemu \
@@ -62,6 +61,7 @@ case "$arch" in
     cmd="$qemu_common \
       -M pc \
       -append 'root=/dev/vda $extra_append' \
+      -device edu \
       -drive file=${images_dir}/rootfs.ext2,if=virtio,format=raw \
       -kernel ${images_dir}/bzImage \
       -net nic,model=virtio \

setoutarch

@@ -1,10 +0,0 @@
-#!/usr/bin/env bash
-# Maintain different buildroot/output archs with symlinks.
-if [ "$#" -ne 1 ]; then
-  exit 1
-fi
-arch="$1"
-dst="output.${arch}~"
-src='buildroot/output'
-mkdir -p "buildroot/$dst"
-ln -fns "$dst" "$src"