[PATCH bpf-next v2 1/2] selftests/bpf: Enable vmtest for cross-compile arm64 on x86_64 host, and fix some issues.

[Lin Yikai <yikai.lin@xxxxxxxx>]

In Makefile, we use $(SRCARCH) to access target arch's uapi include.
This allow us to obtain the definition of 'struct user_pt_regs' for "ptrace.h" header file.

Thus, it is no longer necessary to execute "make headers_install".

Signed-off-by: Lin Yikai <yikai.lin@xxxxxxxx>
---
 tools/testing/selftests/bpf/Makefile   |  6 +++++
 tools/testing/selftests/bpf/README.rst | 11 +++++++-
 tools/testing/selftests/bpf/vmtest.sh  | 37 +++++++++++++++++++++-----
 3 files changed, 47 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index c120617b64ad..3f0f9a171651 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -444,6 +444,7 @@ CLANG_TARGET_ARCH = --target=$(notdir $(CROSS_COMPILE:%-=%))
 endif
 
 CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG),$(CLANG_TARGET_ARCH))
+
 BPF_CFLAGS = -g -Wall -Werror -D__TARGET_ARCH_$(SRCARCH) $(MENDIAN)	\
 	     -I$(INCLUDE_DIR) -I$(CURDIR) -I$(APIDIR)			\
 	     -I$(abspath $(OUTPUT)/../usr/include)			\
@@ -452,6 +453,11 @@ BPF_CFLAGS = -g -Wall -Werror -D__TARGET_ARCH_$(SRCARCH) $(MENDIAN)	\
 
 CLANG_CFLAGS = $(CLANG_SYS_INCLUDES)
 
+ifneq ($(CROSS_COMPILE),)
+src_uapi_dir := $(srctree)/arch/$(SRCARCH)/include/uapi
+BPF_CFLAGS += -I$(src_uapi_dir)
+endif
+
 $(OUTPUT)/test_l4lb_noinline.o: BPF_CFLAGS += -fno-inline
 $(OUTPUT)/test_xdp_noinline.o: BPF_CFLAGS += -fno-inline
 
diff --git a/tools/testing/selftests/bpf/README.rst b/tools/testing/selftests/bpf/README.rst
index 9b974e425af3..41ab23bd3277 100644
--- a/tools/testing/selftests/bpf/README.rst
+++ b/tools/testing/selftests/bpf/README.rst
@@ -79,13 +79,22 @@ In case of linker errors when running selftests, try using static linking:
 
   $ LDLIBS=-static PKG_CONFIG='pkg-config --static' vmtest.sh
 
+If you want to make corss-compile, such as compile arm64 on x86_64, you can try:
+
+.. code-block:: console
+
+  $ export PATH=$PATH:{The corss-compile's path}/bin
+  $ export ARCH=arm64
+  $ export CROSS_COMPILE=aarch64-linux-gnu-
+  $ LDLIBS=-static vmtest.sh
+
 .. note:: Some distros may not support static linking.
 
 .. note:: The script uses pahole and clang based on host environment setting.
           If you want to change pahole and llvm, you can change `PATH` environment
           variable in the beginning of script.
 
-.. note:: The script currently only supports x86_64 and s390x architectures.
+.. note:: The script currently only supports x86_64, s390x and arm64 architectures.
 
 Additional information about selftest failures are
 documented here.
diff --git a/tools/testing/selftests/bpf/vmtest.sh b/tools/testing/selftests/bpf/vmtest.sh
index 65d14f3bbe30..c7461ed496ab 100755
--- a/tools/testing/selftests/bpf/vmtest.sh
+++ b/tools/testing/selftests/bpf/vmtest.sh
@@ -4,11 +4,11 @@
 set -u
 set -e
 
-# This script currently only works for x86_64 and s390x, as
+# This script currently only works for x86_64, s390x and arm64, as
 # it is based on the VM image used by the BPF CI, which is
 # available only for these architectures.
-ARCH="$(uname -m)"
-case "${ARCH}" in
+HOST_ARCH="$(uname -m)"
+case "${HOST_ARCH}" in
 s390x)
 	QEMU_BINARY=qemu-system-s390x
 	QEMU_CONSOLE="ttyS1"
@@ -32,13 +32,38 @@ aarch64)
 	exit 1
 	;;
 esac
+
+# process CROSS_COMPILE setting to enable cross-compilation
+process_cross_compile() {
+	if [ -z "${CROSS_COMPILE+x}" ]; then
+		return
+	fi
+	case "$1" in
+		x86_64)
+			#Cross-compiling for arm64 on an x86_64 host
+			if [[ $CROSS_COMPILE == *aarch64* ]]; then
+				VM_ARCH=aarch64
+				QEMU_CONSOLE="ttyAMA0,115200"
+				QEMU_BINARY=qemu-system-aarch64
+				QEMU_FLAGS=(-M virt,gic-version=3 -cpu cortex-a57 -smp 8)
+				BZIMAGE="arch/arm64/boot/Image"
+				echo "Setting VM_ARCH from $HOST_ARCH to $VM_ARCH as specified by CROSS_COMPILE"
+			fi
+			;;
+	esac
+}
+
+VM_ARCH=${HOST_ARCH}
+process_cross_compile "$VM_ARCH"
+
+
 DEFAULT_COMMAND="./test_progs"
 MOUNT_DIR="mnt"
 ROOTFS_IMAGE="root.img"
 OUTPUT_DIR="$HOME/.bpf_selftests"
 KCONFIG_REL_PATHS=("tools/testing/selftests/bpf/config"
 	"tools/testing/selftests/bpf/config.vm"
-	"tools/testing/selftests/bpf/config.${ARCH}")
+	"tools/testing/selftests/bpf/config.${VM_ARCH}")
 INDEX_URL="https://raw.githubusercontent.com/libbpf/ci/master/INDEX";
 NUM_COMPILE_JOBS="$(nproc)"
 LOG_FILE_BASE="$(date +"bpf_selftests.%Y-%m-%d_%H-%M-%S")"
@@ -109,7 +134,7 @@ newest_rootfs_version()
 {
 	{
 	for file in "${!URLS[@]}"; do
-		if [[ $file =~ ^"${ARCH}"/libbpf-vmtest-rootfs-(.*)\.tar\.zst$ ]]; then
+		if [[ $file =~ ^"${VM_ARCH}"/libbpf-vmtest-rootfs-(.*)\.tar\.zst$ ]]; then
 			echo "${BASH_REMATCH[1]}"
 		fi
 	done
@@ -126,7 +151,7 @@ download_rootfs()
 		exit 1
 	fi
 
-	download "${ARCH}/libbpf-vmtest-rootfs-$rootfsversion.tar.zst" |
+	download "${VM_ARCH}/libbpf-vmtest-rootfs-$rootfsversion.tar.zst" |
 		zstd -d | sudo tar -C "$dir" -x
 }
 
-- 
2.34.1