Re: [PATCH bpf-next 2/3] libbpf/tools: add runqslower tool to libbpf

[Yonghong Song <yhs@fb.com>]

On 12/18/19 11:06 PM, Andrii Nakryiko wrote:
> Convert one of BCC tools (runqslower [0]) to BPF CO-RE + libbpf. It matches
> its BCC-based counterpart 1-to-1, supporting all the same parameters and
> functionality.
> 
> runqslower tool utilizes BPF skeleton, auto-generated from BPF object file,
> as well as memory-mapped interface to global (read-only, in this case) data.
> Its makefile also ensures auto-generation of "relocatable" vmlinux.h, which is
> necessary for BTF-typed raw tracepoints with direct memory access.
> 
>    [0] https://github.com/iovisor/bcc/blob/11bf5d02c895df9646c117c713082eb192825293/tools/runqslower.py
> 
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> ---
>   tools/lib/bpf/tools/runqslower/.gitignore     |   2 +
>   tools/lib/bpf/tools/runqslower/Makefile       |  60 ++++++
>   .../lib/bpf/tools/runqslower/runqslower.bpf.c | 101 ++++++++++
>   tools/lib/bpf/tools/runqslower/runqslower.c   | 187 ++++++++++++++++++
>   tools/lib/bpf/tools/runqslower/runqslower.h   |  13 ++
>   5 files changed, 363 insertions(+)
>   create mode 100644 tools/lib/bpf/tools/runqslower/.gitignore
>   create mode 100644 tools/lib/bpf/tools/runqslower/Makefile
>   create mode 100644 tools/lib/bpf/tools/runqslower/runqslower.bpf.c
>   create mode 100644 tools/lib/bpf/tools/runqslower/runqslower.c
>   create mode 100644 tools/lib/bpf/tools/runqslower/runqslower.h
> 
> diff --git a/tools/lib/bpf/tools/runqslower/.gitignore b/tools/lib/bpf/tools/runqslower/.gitignore
> new file mode 100644
> index 000000000000..404942cc9371
> --- /dev/null
> +++ b/tools/lib/bpf/tools/runqslower/.gitignore
> @@ -0,0 +1,2 @@
> +/.output
> +/runqslower
> diff --git a/tools/lib/bpf/tools/runqslower/Makefile b/tools/lib/bpf/tools/runqslower/Makefile
> new file mode 100644
> index 000000000000..b87b1f9fe9da
> --- /dev/null
> +++ b/tools/lib/bpf/tools/runqslower/Makefile
> @@ -0,0 +1,60 @@
> +# SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
> +CLANG := clang
> +LLC := llc
> +LLVM_STRIP := llvm-strip
> +BPFTOOL := bpftool

Maybe it is better to use in-tree bpftool? This will ensure we use the 
one shipped together with the source which should have needed functionality.

> +LIBBPF_SRC := ../..
> +CFLAGS := -g -Wall
> +
> +# Try to detect best kernel BTF source
> +KERNEL_REL := $(shell uname -r)
> +ifneq ("$(wildcard /sys/kenerl/btf/vmlinux)","")
> +VMLINUX_BTF := /sys/kernel/btf/vmlinux
> +else ifneq ("$(wildcard /boot/vmlinux-$(KERNEL_REL))","")
> +VMLINUX_BTF := /boot/vmlinux-$(KERNEL_REL)
> +else
> +$(error "Can't detect kernel BTF, use VMLINUX_BTF to specify it explicitly")
> +endif
> +
> +out := .output
> +abs_out := $(abspath $(out))
> +libbpf_src := $(abspath $(LIBBPF_SRC))
> +
> +.DELETE_ON_ERROR:
> +
> +.PHONY: all
> +all: runqslower
> +
> +.PHONY: clean
> +clean:
> +	rm -rf $(out) runqslower
> +
> +runqslower: $(out)/runqslower.o $(out)/libbpf.a
> +	$(CC) $(CFLAGS) -lelf -lz $^ -o $@
> +
> +$(out)/vmlinux.h: $(VMLINUX_BTF) | $(out)
> +	$(BPFTOOL) btf dump file $(VMLINUX_BTF) format core > $@
> +
> +$(out)/libbpf.a: | $(out)
> +	cd $(out) &&							      \
> +	$(MAKE) -C $(libbpf_src) OUTPUT=$(abs_out)/ $(abs_out)/libbpf.a
> +
> +$(out)/runqslower.o: runqslower.h $(out)/runqslower.skel.h		      \
> +		     $(out)/runqslower.bpf.o
> +
> +$(out)/runqslower.bpf.o: $(out)/vmlinux.h runqslower.h
> +
> +$(out)/%.skel.h: $(out)/%.bpf.o
> +	$(BPFTOOL) gen skeleton $< > $@
> +
> +$(out)/%.bpf.o: %.bpf.c | $(out)
> +	$(CLANG) -g -O2 -target bpf -I$(out) -I$(LIBBPF_SRC)		      \
> +		 -c $(filter %.c,$^) -o $@ &&				      \
> +	$(LLVM_STRIP) -g $@
> +
> +$(out)/%.o: %.c | $(out)
> +	$(CC) $(CFLAGS) -I$(LIBBPF_SRC) -I$(out) -c $(filter %.c,$^) -o $@
> +
> +$(out):
> +	mkdir -p $(out)
> +
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