linux-kernel - Re: [PATCH] samples/bpf: Add BTF build flags to Makefile

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Message-ID: <67fd8ddc-088e-469a-d093-b92f637cab11@gmail.com>
Date:   Thu, 26 Jul 2018 19:08:41 +0900
From:   Taeung Song <treeze.taeung@...il.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Martin KaFai Lau <kafai@...com>
Subject: Re: [PATCH] samples/bpf: Add BTF build flags to Makefile



On 07/26/2018 10:16 AM, Jakub Kicinski wrote:
> On Thu, 26 Jul 2018 01:30:39 +0900, Taeung Song wrote:
>> To smoothly test BTF supported binary on samples/bpf,
>> let samples/bpf/Makefile probe llc, pahole and
>> llvm-objcopy for BPF support and use them
>> like tools/testing/selftests/bpf/Makefile
>> changed from the commit c0fa1b6c3efc ("bpf: btf:
>>   Add BTF tests")
>>
>> Cc: Martin KaFai Lau <kafai@...com>
>> Signed-off-by: Taeung Song <treeze.taeung@...il.com>
>> ---
>>   samples/bpf/Makefile | 21 ++++++++++++++++++++-
>>   1 file changed, 20 insertions(+), 1 deletion(-)
>>
>> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
>> index 1303af10e54d..e079266360a3 100644
>> --- a/samples/bpf/Makefile
>> +++ b/samples/bpf/Makefile
>> @@ -191,6 +191,8 @@ HOSTLOADLIBES_xdpsock		+= -pthread
>>   #  make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
>>   LLC ?= llc
>>   CLANG ?= clang
>> +LLVM_OBJCOPY ?= llvm-objcopy
>> +BTF_PAHOLE ?= pahole
>>   
>>   # Detect that we're cross compiling and use the cross compiler
>>   ifdef CROSS_COMPILE
>> @@ -198,6 +200,20 @@ HOSTCC = $(CROSS_COMPILE)gcc
>>   CLANG_ARCH_ARGS = -target $(ARCH)
>>   endif
>>   
>> +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 $(LLVM_OBJCOPY) --help 2>&1 | grep -i 'usage.*llvm')
>> +
>> +ifneq ($(BTF_LLC_PROBE),)
>> +ifneq ($(BTF_PAHOLE_PROBE),)
>> +ifneq ($(BTF_OBJCOPY_PROBE),)
> 
> Nice patch!  FWIW you could consider using $(and ...) here:
> 
> ifneq ($(and $(BTF_LLC_PROBE),$(BTF_PAHOLE_PROBE),$(BTF_OBJCOPY_PROBE)),)
> 
> https://www.gnu.org/software/make/manual/html_node/Conditional-Functions.html#Conditional-Functions
> 
> Not sure it's worth a respin..
> 

Hi Jakub,

Thanks for reviewing this.
I also think the conditional functions looks more tidy, will change it!

Thanks,
Taeung

>> +	EXTRA_CFLAGS += -g
>> +	LLC_FLAGS += -mattr=dwarfris
>> +	DWARF2BTF = y
>> +endif
>> +endif
>> +endif
>> +
>>   # Trick to allow make to be run from this directory
>>   all:
>>   	$(MAKE) -C ../../ $(CURDIR)/ BPF_SAMPLES_PATH=$(CURDIR)
>> @@ -256,4 +272,7 @@ $(obj)/%.o: $(src)/%.c
>>   		-Wno-gnu-variable-sized-type-not-at-end \
>>   		-Wno-address-of-packed-member -Wno-tautological-compare \
>>   		-Wno-unknown-warning-option $(CLANG_ARCH_ARGS) \
>> -		-O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf -filetype=obj -o $@
>> +		-O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@
>> +ifeq ($(DWARF2BTF),y)
>> +	$(BTF_PAHOLE) -J $@
>> +endif