[PATCH bpf-next 0/2] selftests/bpf Makefile cleanup and fixes

[PATCH bpf-next 0/2] selftests/bpf Makefile cleanup and fixes

[Andrii Nakryiko]

Patch #1 enforces libbpf build to have bpf_helper_defs.h ready before test BPF
programs are built.
Patch #2 drops obsolete BTF/pahole detection logic from Makefile.

Andrii Nakryiko (2):
  selftests/bpf: enforce libbpf build before BPF programs are built
  selftests/bpf: remove obsolete pahole/BTF support detection

 tools/testing/selftests/bpf/Makefile | 47 +++++-----------------------
 1 file changed, 8 insertions(+), 39 deletions(-)

-- 
2.17.1

[PATCH bpf-next 1/2] selftests/bpf: enforce libbpf build before BPF programs are built

[Andrii Nakryiko]

Given BPF programs rely on libbpf's bpf_helper_defs.h, which is
auto-generated during libbpf build, libbpf build has to happen before
we attempt progs/*.c build. Enforce it as order-only dependency.

Fixes: 24f25763d6de ("libbpf: auto-generate list of BPF helper definitions")
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 tools/testing/selftests/bpf/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 40552fb441e5..f958643d36da 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -256,7 +256,8 @@ ifeq ($(DWARF2BTF),y)
 	$(BTF_PAHOLE) -J $@
 endif
 
-$(OUTPUT)/%.o: progs/%.c
+# libbpf has to be built before BPF programs due to bpf_helper_defs.h
+$(OUTPUT)/%.o: progs/%.c | $(BPFOBJ)
 	($(CLANG) $(BPF_CFLAGS) $(CLANG_CFLAGS) -O2 -target bpf -emit-llvm \
 		-c $< -o - || echo "clang failed") | \
 	$(LLC) -march=bpf -mcpu=$(CPU) $(LLC_FLAGS) -filetype=obj -o $@
-- 
2.17.1

[PATCH bpf-next 2/2] selftests/bpf: remove obsolete pahole/BTF support detection

[Andrii Nakryiko]

Given lots of selftests won't work without recent enough Clang/LLVM that
fully supports BTF, there is no point in maintaining outdated BTF
support detection and fall-back to pahole logic. Just assume we have
everything we need.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 tools/testing/selftests/bpf/Makefile | 44 ++++------------------------
 1 file changed, 6 insertions(+), 38 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index f958643d36da..d1770da2da70 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -15,8 +15,6 @@ endif
 CLANG		?= clang
 LLC		?= llc
 LLVM_OBJCOPY	?= llvm-objcopy
-LLVM_READELF	?= llvm-readelf
-BTF_PAHOLE	?= pahole
 BPF_GCC		?= $(shell command -v bpf-gcc;)
 CFLAGS += -g -Wall -O2 -I$(APIDIR) -I$(LIBDIR) -I$(BPFDIR) -I$(GENDIR) $(GENFLAGS) -I../../../include \
 	  -Dbpf_prog_load=bpf_prog_test_load \
@@ -147,8 +145,9 @@ $(shell $(1) -v -E - </dev/null 2>&1 \
 	| sed -n '/<...> search starts here:/,/End of search list./{ s| \(/.*\)|-idirafter \1|p }')
 endef
 CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG))
-BPF_CFLAGS = -I. -I./include/uapi -I../../../include/uapi \
-	     -I$(BPFDIR) -I$(OUTPUT)/../usr/include -D__TARGET_ARCH_$(SRCARCH)
+BPF_CFLAGS = -g -D__TARGET_ARCH_$(SRCARCH) 				\
+	     -I. -I./include/uapi -I../../../include/uapi 		\
+	     -I$(BPFDIR) -I$(OUTPUT)/../usr/include
 
 CLANG_CFLAGS = $(CLANG_SYS_INCLUDES) \
 	       -Wno-compare-distinct-pointer-types
@@ -162,28 +161,6 @@ $(OUTPUT)/test_stack_map.o: test_queue_stack_map.h
 $(OUTPUT)/flow_dissector_load.o: flow_dissector_load.h
 $(OUTPUT)/test_progs.o: flow_dissector_load.h
 
-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')
-BTF_LLVM_PROBE := $(shell echo "int main() { return 0; }" | \
-			  $(CLANG) -target bpf -O2 -g -c -x c - -o ./llvm_btf_verify.o; \
-			  $(LLVM_READELF) -S ./llvm_btf_verify.o | grep BTF; \
-			  /bin/rm -f ./llvm_btf_verify.o)
-
-ifneq ($(BTF_LLVM_PROBE),)
-	BPF_CFLAGS += -g
-else
-ifneq ($(BTF_LLC_PROBE),)
-ifneq ($(BTF_PAHOLE_PROBE),)
-ifneq ($(BTF_OBJCOPY_PROBE),)
-	BPF_CFLAGS += -g
-	LLC_FLAGS += -mattr=dwarfris
-	DWARF2BTF = y
-endif
-endif
-endif
-endif
-
 TEST_PROGS_CFLAGS := -I. -I$(OUTPUT)
 TEST_MAPS_CFLAGS := -I. -I$(OUTPUT)
 TEST_VERIFIER_CFLAGS := -I. -I$(OUTPUT) -Iverifier
@@ -212,11 +189,8 @@ $(ALU32_BUILD_DIR)/%.o: progs/%.c $(ALU32_BUILD_DIR)/test_progs_32 \
 					| $(ALU32_BUILD_DIR)
 	($(CLANG) $(BPF_CFLAGS) $(CLANG_CFLAGS) -O2 -target bpf -emit-llvm \
 		-c $< -o - || echo "clang failed") | \
-	$(LLC) -march=bpf -mattr=+alu32 -mcpu=$(CPU) $(LLC_FLAGS) \
+	$(LLC) -march=bpf -mcpu=probe -mattr=+alu32 $(LLC_FLAGS) \
 		-filetype=obj -o $@
-ifeq ($(DWARF2BTF),y)
-	$(BTF_PAHOLE) -J $@
-endif
 endif
 
 ifneq ($(BPF_GCC),)
@@ -251,19 +225,13 @@ endif
 $(OUTPUT)/test_xdp.o: progs/test_xdp.c
 	($(CLANG) $(BPF_CFLAGS) $(CLANG_CFLAGS) -O2 -emit-llvm -c $< -o - || \
 		echo "clang failed") | \
-	$(LLC) -march=bpf -mcpu=$(CPU) $(LLC_FLAGS) -filetype=obj -o $@
-ifeq ($(DWARF2BTF),y)
-	$(BTF_PAHOLE) -J $@
-endif
+	$(LLC) -march=bpf -mcpu=probe $(LLC_FLAGS) -filetype=obj -o $@
 
 # libbpf has to be built before BPF programs due to bpf_helper_defs.h
 $(OUTPUT)/%.o: progs/%.c | $(BPFOBJ)
 	($(CLANG) $(BPF_CFLAGS) $(CLANG_CFLAGS) -O2 -target bpf -emit-llvm \
 		-c $< -o - || echo "clang failed") | \
-	$(LLC) -march=bpf -mcpu=$(CPU) $(LLC_FLAGS) -filetype=obj -o $@
-ifeq ($(DWARF2BTF),y)
-	$(BTF_PAHOLE) -J $@
-endif
+	$(LLC) -march=bpf -mcpu=probe $(LLC_FLAGS) -filetype=obj -o $@
 
 PROG_TESTS_DIR = $(OUTPUT)/prog_tests
 $(PROG_TESTS_DIR):
-- 
2.17.1

Re: [Potential Spoof] [PATCH bpf-next 2/2] selftests/bpf: remove obsolete pahole/BTF support detection

[Martin Lau]

On Thu, Oct 10, 2019 at 08:13:18PM -0700, Andrii Nakryiko wrote:
> Given lots of selftests won't work without recent enough Clang/LLVM that
> fully supports BTF, there is no point in maintaining outdated BTF
> support detection and fall-back to pahole logic. Just assume we have
> everything we need.
May be an error message to tell which llvm is needed?

$(CPU) and $(PROBE) are no longer needed also?

Re: [Potential Spoof] [PATCH bpf-next 2/2] selftests/bpf: remove obsolete pahole/BTF support detection

[Andrii Nakryiko]

On Fri, Oct 11, 2019 at 9:21 AM Martin Lau <kafai@fb.com> wrote:
>
> On Thu, Oct 10, 2019 at 08:13:18PM -0700, Andrii Nakryiko wrote:
> > Given lots of selftests won't work without recent enough Clang/LLVM that
> > fully supports BTF, there is no point in maintaining outdated BTF
> > support detection and fall-back to pahole logic. Just assume we have
> > everything we need.
> May be an error message to tell which llvm is needed?

Not sure where we'd want this to be checked/printed. We don't do this
today, so what I'm doing here is not really a regression.
There is no single llvm version I'd want to pin down. For most tests
LLVM w/ basic BTF support would be enough, for CO-RE stuff we need the
latest Clang 10 (not yet released officially), though. So essentially
the stance right now is that you need latest Clang built from sources
to have all the tests compiled and I don't think it's easy to check
for that.

>
> $(CPU) and $(PROBE) are no longer needed also?

Good catch, removing them as well.

Re: [PATCH bpf-next 1/2] selftests/bpf: enforce libbpf build before BPF programs are built

[Martin Lau]

On Thu, Oct 10, 2019 at 08:13:17PM -0700, Andrii Nakryiko wrote:
> Given BPF programs rely on libbpf's bpf_helper_defs.h, which is
> auto-generated during libbpf build, libbpf build has to happen before
> we attempt progs/*.c build. Enforce it as order-only dependency.
Acked-by: Martin KaFai Lau <kafai@fb.com>

Re: [Potential Spoof] [PATCH bpf-next 2/2] selftests/bpf: remove obsolete pahole/BTF support detection

[Daniel Borkmann]

On Fri, Oct 11, 2019 at 10:28:39AM -0700, Andrii Nakryiko wrote:
> On Fri, Oct 11, 2019 at 9:21 AM Martin Lau <kafai@fb.com> wrote:
> > On Thu, Oct 10, 2019 at 08:13:18PM -0700, Andrii Nakryiko wrote:
> > > Given lots of selftests won't work without recent enough Clang/LLVM that
> > > fully supports BTF, there is no point in maintaining outdated BTF
> > > support detection and fall-back to pahole logic. Just assume we have
> > > everything we need.
> > May be an error message to tell which llvm is needed?
> 
> Not sure where we'd want this to be checked/printed. We don't do this
> today, so what I'm doing here is not really a regression.
> There is no single llvm version I'd want to pin down. For most tests
> LLVM w/ basic BTF support would be enough, for CO-RE stuff we need the
> latest Clang 10 (not yet released officially), though. So essentially
> the stance right now is that you need latest Clang built from sources
> to have all the tests compiled and I don't think it's easy to check
> for that.

At some point once bpf-gcc gets more mature, we might need something
more elaborate than just telling everyone to use latest clang/llvm
from git, but so far that's our convention we have in place today.

> > $(CPU) and $(PROBE) are no longer needed also?
> 
> Good catch, removing them as well.

Ok, expecting v2 then.

Thanks,
Daniel