Re: [RFC PATCH v2 08/10] selftests: conditionally enable XDP support in udpgso_bench_rx

XDP support will be used by a later patch to test the GRO path
in a net namespace, leveraging the veth XDP implementation.
To avoid breaking existing setup, XDP support is conditionally
enabled and build only if llc is locally available.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---

diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index 256d82d5fa87..176459b7c4d6 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile

@@ -16,8 +16,77 @@ TEST_GEN_PROGS = reuseport_bpf reuseport_bpf_cpu reuseport_bpf_numa
 TEST_GEN_PROGS += reuseport_dualstack reuseaddr_conflict tls

 KSFT_KHDR_INSTALL := 1
+
+# Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
+#  make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
+LLC ?= llc
+CLANG ?= clang
+LLVM_OBJCOPY ?= llvm-objcopy
+BTF_PAHOLE ?= pahole
+HAS_LLC := $(shell which $(LLC) 2>/dev/null)
+
+# conditional enable testes requiring llc
+ifneq (, $(HAS_LLC))
+TEST_GEN_FILES += xdp_dummy.o
+endif
+
 include ../lib.mk

+ifneq (, $(HAS_LLC))
+
+# Detect that we're cross compiling and use the cross compiler
+ifdef CROSS_COMPILE
+CLANG_ARCH_ARGS = -target $(ARCH)
+endif
+
+PROBE := $(shell $(LLC) -march=bpf -mcpu=probe -filetype=null /dev/null 2>&1)
+
+# Let newer LLVM versions transparently probe the kernel for availability
+# of full BPF instruction set.
+ifeq ($(PROBE),)
+  CPU ?= probe
+else
+  CPU ?= generic
+endif
+
+SRC_PATH := $(abspath ../../../..)
+LIB_PATH := $(SRC_PATH)/tools/lib
+XDP_CFLAGS := -D SUPPORT_XDP=1 -I$(LIB_PATH)
+LIBBPF = $(LIB_PATH)/bpf/libbpf.a
+BTF_LLC_PROBE := $(shell $(LLC) -march=bpf -mattr=help 2>&1 | grep dwarfris)
+BTF_PAHOLE_PROBE := $(shell $(BTF_PAHOLE) --help 2>&1 | grep BTF)
+BTF_OBJCOPY_PROBE := $(shell $(LLVM_OBJCOPY) --help 2>&1 | grep -i 'usage.*llvm')
+CLANG_SYS_INCLUDES := $(shell $(CLANG) -v -E - </dev/null 2>&1 \
+        | sed -n '/<...> search starts here:/,/End of search list./{ s| \(/.*\)|-idirafter \1|p }')
+CLANG_FLAGS = -I. -I$(SRC_PATH)/include -I../bpf/ \
+             $(CLANG_SYS_INCLUDES) -Wno-compare-distinct-pointer-types
+
+ifneq ($(and $(BTF_LLC_PROBE),$(BTF_PAHOLE_PROBE),$(BTF_OBJCOPY_PROBE)),)
+       CLANG_CFLAGS += -g
+       LLC_FLAGS += -mattr=dwarfris
+       DWARF2BTF = y
+endif
+
+$(LIBBPF): FORCE
+# Fix up variables inherited from Kbuild that tools/ build system won't like
+       $(MAKE) -C $(dir $@) RM='rm -rf' LDFLAGS= srctree=$(SRC_PATH) O= $(nodir $@)
+

--- a/tools/testing/selftests/net/udpgso_bench_rx.c

@@ -227,6 +234,13 @@ static void parse_opts(int argc, char **argv)
                        cfg_verify = true;
                        cfg_read_all = true;
                        break;
+#ifdef SUPPORT_XDP
+               case 'x':
+                       cfg_xdp_iface = if_nametoindex(optarg);
+                       if (!cfg_xdp_iface)
+                               error(1, errno, "unknown interface %s", optarg);
+                       break;
+#endif