linux-kernel - Re: [RFC 1/2] perf: support build BPF skeletons with perf

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Date:   Tue, 24 Nov 2020 20:51:22 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Song Liu <songliubraving@...com>
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com,
        peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        namhyung@...nel.org
Subject: Re: [RFC 1/2] perf: support build BPF skeletons with perf

On Wed, Nov 18, 2020 at 08:50:45PM -0800, Song Liu wrote:

SNIP

> +	$(Q)$(BPFTOOL) gen skeleton $< > $@
> +
> +$(TMP_OUTPUT)/%.bpf.o: %.bpf.c $(TMP_OUTPUT)/vmlinux.h $(BPFOBJ) | $(TMP_OUTPUT)
> +	$(call msg,BPF,$@)
> +	$(Q)$(CLANG) -g -O2 -target bpf $(INCLUDES)			      \
> +		 -c $(filter %.c,$^) -o $@ &&				      \
> +	$(LLVM_STRIP) -g $@
> +
> +$(TMP_OUTPUT):
> +	$(call msg,MKDIR,$@)
> +	$(Q)mkdir -p $(TMP_OUTPUT)
> +
> +$(TMP_OUTPUT)/vmlinux.h: $(VMLINUX_BTF_PATH) | $(TMP_OUTPUT) $(BPFTOOL)

please add support to specify VMLINUX_H as it is in selftests
or bpftool, we will need it in out building setup

thanks,
jirka

> +	$(call msg,GEN,$@)
> +	$(Q)if [ ! -e "$(VMLINUX_BTF_PATH)" ] ; then \
> +		echo "Couldn't find kernel BTF; set VMLINUX_BTF to"	       \
> +			"specify its location." >&2;			       \
> +		exit 1;\
> +	fi
> +	$(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF_PATH) format c > $@
> +
> +$(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(TMP_OUTPUT)
> +	$(Q)$(MAKE) $(submake_extras) -C $(LIBBPF_SRC)			       \
> +		    OUTPUT=$(abspath $(dir $@))/ $(abspath $@)
> +
> +$(DEFAULT_BPFTOOL): | $(TMP_OUTPUT)
> +	$(Q)$(MAKE) $(submake_extras) -C ../../../bpf/bpftool		      \
> +		    prefix= OUTPUT=$(TMP_OUTPUT)/ DESTDIR=$(TMP_OUTPUT) install
> diff --git a/tools/perf/util/bpf_skel/dummy.bpf.c b/tools/perf/util/bpf_skel/dummy.bpf.c
> new file mode 100644
> index 0000000000000..085fcee1f52cf
> --- /dev/null
> +++ b/tools/perf/util/bpf_skel/dummy.bpf.c
> @@ -0,0 +1,19 @@
> +// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +// Copyright (c) 2020 Facebook
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +
> +struct {
> +	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
> +	__uint(key_size, sizeof(u32));
> +	__uint(value_size, sizeof(u64));
> +} counts SEC(".maps");
> +
> +SEC("fentry/dummy")
> +int BPF_PROG(fentry_dummy)
> +{
> +	return 0;
> +}
> +
> +char LICENSE[] SEC("license") = "Dual BSD/GPL";
> -- 
> 2.24.1
>