Mark Brown broonie@kernel.org writes:
On Mon, Oct 07, 2024 at 09:31:32AM +0200, Björn Töpel wrote:
When building the kselftest suite, e.g.:
make ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- \ SKIP_TARGETS="" O=/output/foo -C tools/testing/selftests install
The expectation is that the sched_ext is included, cross-built, and placed into /output/foo.
When building for arm64 with this applied on top of mainline or -next I'm seeing:
Thanks for taking it for a spin!
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -C tools/testing/selftests TARGETS=sched_ext SKIP_TARGETS="
give
CLNG-BPF create_dsq.bpf.o In file included from create_dsq.bpf.c:9: /home/broonie/git/linux/tools/sched_ext/include/scx/common.bpf.h:33:17: error: use of undeclared identifier 'SCX_DSQ_FLAG_BUILTIN' 33 | _Static_assert(SCX_DSQ_FLAG_BUILTIN, | ^
This is most likely due to incorrect VMLINUX_BTF_PATHS, so that vmlinux.h is incorrectly generated. Try grepping for SCX_DSQ_FLAG_BUILTIN in vmlinux.h.
and more (my system clang is clang 20). It's also failing with a native x86_64 build in the same way. I've run "make headers_install", it looks like clang is not getting told about the copy of the headers installed in ./usr/include:
clang -g -D__TARGET_ARCH_x86 -mlittle-endian -I/home/broonie/git/linux/tools/testing/selftests/sched_ext/include -I/home/broonie/git/linux/tools/testing/selftests/sched_ext/include/bpf-compat -I/home/broonie/git/linux/tools/testing/selftests/sched_ext/build/include -I/home/broonie/git/linux/tools/include/uapi -I/home/broonie/git/linux/tools/sched_ext/include -I/home/broonie/git/linux/include -idirafter /usr/lib/llvm-20/lib/clang/20/include -idirafter /usr/local/include -idirafter /usr/include/x86_64-linux-gnu -idirafter /usr/include -Wall -Wno-compare-distinct-pointer-types -Wno-incompatible-function-pointer-types -O2 -mcpu=v3 -target bpf -c create_dsq.bpf.c -o /home/broonie/git/linux/tools/testing/selftests/sched_ext/build/obj/sched_ext/create_dsq.bpf.o
The sched_ext BPF programs relies on a vmlinux.h, which is generated using bpftool and the vmlinux with BTF information. Have you built a kernel with BTF support?
Add CROSS_COMPILE, OUTPUT, and TARGETS support to the sched_ext selftest. Also, remove some variables that were unused by the Makefile.
+ifneq ($(CROSS_COMPILE),) +DEFAULT_BPFTOOL := $(OUTPUT_DIR)/host/sbin/bpftool +HOST_OBJ_DIR := $(OBJ_DIR)/host/bpftool +HOST_LIBBPF_OUTPUT := $(OBJ_DIR)/host/libbpf/ +HOST_LIBBPF_DESTDIR := $(OUTPUT_DIR)/host/ +HOST_DESTDIR := $(OUTPUT_DIR)/host/ +else +DEFAULT_BPFTOOL := $(OUTPUT_DIR)/sbin/bpftool +HOST_OBJ_DIR := $(OBJ_DIR)/bpftool +HOST_LIBBPF_OUTPUT := $(OBJ_DIR)/libbpf/ +HOST_LIBBPF_DESTDIR := $(OUTPUT_DIR)/ +HOST_DESTDIR := $(OUTPUT_DIR)/ +endif
This won't detect a cross compile when building using LLVM as that doesn't need to set CROSS_COMPILE, it can use the same binaries for all targets. There's runes in the Makefile for the mm selftests for identifying the target architecture, though actually I'm wondering if it's worth just always building the host copy and never having to worry if the target build is a cross build or not? It's obvious overhead in the native case though if we actually need the target copy.
Yeah, that would indeed simplify things! I'll spin a v3 with that (and wait for more feedback).
Thanks for testing the patch! Björn