selftests/bpf: Fix broken riscv build

The selftests/bpf Makefile includes system include directories from
the host, when building BPF programs. On RISC-V glibc requires that
__riscv_xlen is defined. This is not the case for "clang -target bpf",
which messes up __WORDSIZE (errno.h -> ... -> wordsize.h) and breaks
the build.

By explicitly defining __risc_xlen correctly for riscv, we can
workaround this.

Fixes: 167381f3eac0 ("selftests/bpf: Makefile fix "missing" headers on build with -idirafter")
Signed-off-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Luke Nelson <luke.r.nels@gmail.com>
Link: https://lore.kernel.org/bpf/20201118071640.83773-2-bjorn.topel@gmail.com

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index c1708ffa6b1cbae1d59d42a831bb1245eb1ac983..3d5940cd110d5a693d86c78f4d35f3a47c206731 100644 (file)
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -219,7 +219,8 @@ $(RESOLVE_BTFIDS): $(BPFOBJ) | $(BUILD_DIR)/resolve_btfids  \
 # build would have failed anyways.
 define get_sys_includes
 $(shell $(1) -v -E - </dev/null 2>&1 \
-       | sed -n '/<...> search starts here:/,/End of search list./{ s| \(/.*\)|-idirafter \1|p }')
+       | sed -n '/<...> search starts here:/,/End of search list./{ s| \(/.*\)|-idirafter \1|p }') \
+$(shell $(1) -dM -E - </dev/null | grep '#define __riscv_xlen ' | sed 's/#define /-D/' | sed 's/ /=/')
 endef
 
 # Determine target endianness.