selftests/bpf: suppress readelf stderr when probing for BTF support

Before:
$ make -s -C tools/testing/selftests/bpf
readelf: Error: Missing knowledge of 32-bit reloc types used in DWARF
sections of machine number 247
readelf: Warning: unable to apply unsupported reloc type 10 to section
.debug_info
readelf: Warning: unable to apply unsupported reloc type 1 to section
.debug_info
readelf: Warning: unable to apply unsupported reloc type 10 to section
.debug_info

After:
$ make -s -C tools/testing/selftests/bpf

v2:
* use llvm-readelf instead of redirecting binutils' readelf stderr to
  /dev/null

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Stanislav Fomichev 2019-01-24 08:54:29 -08:00 committed by Daniel Borkmann
parent d9ff286a0f
commit 2f0921262b

View File

@ -95,6 +95,7 @@ $(BPFOBJ): force
CLANG ?= clang
LLC ?= llc
LLVM_OBJCOPY ?= llvm-objcopy
LLVM_READELF ?= llvm-readelf
BTF_PAHOLE ?= pahole
PROBE := $(shell $(LLC) -march=bpf -mcpu=probe -filetype=null /dev/null 2>&1)
@ -131,7 +132,7 @@ 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; \
readelf -S ./llvm_btf_verify.o | grep BTF; \
$(LLVM_READELF) -S ./llvm_btf_verify.o | grep BTF; \
/bin/rm -f ./llvm_btf_verify.o)
ifneq ($(BTF_LLVM_PROBE),)