2021-10-21 12:39:38

by Pu Lehui

Subject: [PATCH bpf-next] samples: bpf: Suppress readelf stderr when probing for BTF support

When compiling bpf samples, the following warning appears:

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

Same problem was mentioned in commit 2f0921262ba9 ("selftests/bpf:
suppress readelf stderr when probing for BTF support"), let's use
readelf that supports btf.

Signed-off-by: Pu Lehui <[email protected]>
---
samples/bpf/Makefile | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 2366242edb7c..a886dff1ba89 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -229,6 +229,7 @@ CLANG ?= clang
OPT ?= opt
LLVM_DIS ?= llvm-dis
LLVM_OBJCOPY ?= llvm-objcopy
+LLVM_READELF ?= llvm-readelf
BTF_PAHOLE ?= pahole

# Detect that we're cross compiling and use the cross compiler
@@ -252,7 +253,7 @@ 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)

BPF_EXTRA_CFLAGS += -fno-stack-protector
--
2.17.1

2021-10-21 19:22:58

by John Fastabend

Subject: RE: [PATCH bpf-next] samples: bpf: Suppress readelf stderr when probing for BTF support

Pu Lehui wrote:
> When compiling bpf samples, the following warning appears:
>
> 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
>
> Same problem was mentioned in commit 2f0921262ba9 ("selftests/bpf:
> suppress readelf stderr when probing for BTF support"), let's use
> readelf that supports btf.
>
> Signed-off-by: Pu Lehui <[email protected]>
> ---

Thanks.

Acked-by: John Fastabend <[email protected]>

2021-11-03 02:33:32

by Yonghong Song

Subject: Re: [PATCH bpf-next] samples: bpf: Suppress readelf stderr when probing for BTF support

On 10/21/21 5:39 AM, Pu Lehui wrote:
> When compiling bpf samples, the following warning appears:
>
> 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
>
> Same problem was mentioned in commit 2f0921262ba9 ("selftests/bpf:
> suppress readelf stderr when probing for BTF support"), let's use
> readelf that supports btf.
>
> Signed-off-by: Pu Lehui <[email protected]>

Acked-by: Yonghong Song <[email protected]>