Date:   Tue, 17 Sep 2019 16:28:01 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Yonghong Song <yhs@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        john fastabend <john.fastabend@...il.com>,
        open list <linux-kernel@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        clang-built-linux@...glegroups.com,
        sergei.shtylyov@...entembedded.com
Subject: Re: [PATCH v3 bpf-next 08/14] samples: bpf: makefile: base target
 programs rules on Makefile.target

On Mon, Sep 16, 2019 at 3:58 AM Ivan Khoronzhuk
<ivan.khoronzhuk@...aro.org> wrote:
>

Please don't prepend "samples: bpf: makefile:" to patches,
"samples/bpf: " is a typical we've used for BPF samples changes.


> The main reason for that - HOSTCC and CC have different aims.
> HOSTCC is used to build programs running on host, that can
> cross-comple target programs with CC. It was tested for arm and arm64
> cross compilation, based on linaro toolchain, but should work for
> others.
>
> So, in order to split cross compilation (CC) with host build (HOSTCC),
> lets base samples on Makefile.target. It allows to cross-compile
> samples/bpf programs with CC while auxialry tools running on host
> built with HOSTCC.
>
> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
> ---
>  samples/bpf/Makefile | 135 ++++++++++++++++++++++---------------------
>  1 file changed, 69 insertions(+), 66 deletions(-)
>
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index 9d923546e087..1579cc16a1c2 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -4,55 +4,53 @@ BPF_SAMPLES_PATH ?= $(abspath $(srctree)/$(src))
>  TOOLS_PATH := $(BPF_SAMPLES_PATH)/../../tools
>
>  # List of programs to build
> -hostprogs-y := test_lru_dist
> -hostprogs-y += sock_example
> -hostprogs-y += fds_example
> -hostprogs-y += sockex1
> -hostprogs-y += sockex2
> -hostprogs-y += sockex3
> -hostprogs-y += tracex1
> -hostprogs-y += tracex2
> -hostprogs-y += tracex3
> -hostprogs-y += tracex4
> -hostprogs-y += tracex5
> -hostprogs-y += tracex6
> -hostprogs-y += tracex7
> -hostprogs-y += test_probe_write_user
> -hostprogs-y += trace_output
> -hostprogs-y += lathist
> -hostprogs-y += offwaketime
> -hostprogs-y += spintest
> -hostprogs-y += map_perf_test
> -hostprogs-y += test_overhead
> -hostprogs-y += test_cgrp2_array_pin
> -hostprogs-y += test_cgrp2_attach
> -hostprogs-y += test_cgrp2_sock
> -hostprogs-y += test_cgrp2_sock2
> -hostprogs-y += xdp1
> -hostprogs-y += xdp2
> -hostprogs-y += xdp_router_ipv4
> -hostprogs-y += test_current_task_under_cgroup
> -hostprogs-y += trace_event
> -hostprogs-y += sampleip
> -hostprogs-y += tc_l2_redirect
> -hostprogs-y += lwt_len_hist
> -hostprogs-y += xdp_tx_iptunnel
> -hostprogs-y += test_map_in_map
> -hostprogs-y += per_socket_stats_example
> -hostprogs-y += xdp_redirect
> -hostprogs-y += xdp_redirect_map
> -hostprogs-y += xdp_redirect_cpu
> -hostprogs-y += xdp_monitor
> -hostprogs-y += xdp_rxq_info
> -hostprogs-y += syscall_tp
> -hostprogs-y += cpustat
> -hostprogs-y += xdp_adjust_tail
> -hostprogs-y += xdpsock
> -hostprogs-y += xdp_fwd
> -hostprogs-y += task_fd_query
> -hostprogs-y += xdp_sample_pkts
> -hostprogs-y += ibumad
> -hostprogs-y += hbm
> +tprogs-y := test_lru_dist
> +tprogs-y += sock_example
> +tprogs-y += fds_example
> +tprogs-y += sockex1
> +tprogs-y += sockex2
> +tprogs-y += sockex3
> +tprogs-y += tracex1
> +tprogs-y += tracex2
> +tprogs-y += tracex3
> +tprogs-y += tracex4
> +tprogs-y += tracex5
> +tprogs-y += tracex6
> +tprogs-y += tracex7
> +tprogs-y += test_probe_write_user
> +tprogs-y += trace_output
> +tprogs-y += lathist
> +tprogs-y += offwaketime
> +tprogs-y += spintest
> +tprogs-y += map_perf_test
> +tprogs-y += test_overhead
> +tprogs-y += test_cgrp2_array_pin
> +tprogs-y += test_cgrp2_attach
> +tprogs-y += test_cgrp2_sock
> +tprogs-y += test_cgrp2_sock2
> +tprogs-y += xdp1
> +tprogs-y += xdp2
> +tprogs-y += xdp_router_ipv4
> +tprogs-y += test_current_task_under_cgroup
> +tprogs-y += trace_event
> +tprogs-y += sampleip
> +tprogs-y += tc_l2_redirect
> +tprogs-y += lwt_len_hist
> +tprogs-y += xdp_tx_iptunnel
> +tprogs-y += test_map_in_map
> +tprogs-y += xdp_redirect_map
> +tprogs-y += xdp_redirect_cpu
> +tprogs-y += xdp_monitor
> +tprogs-y += xdp_rxq_info
> +tprogs-y += syscall_tp
> +tprogs-y += cpustat
> +tprogs-y += xdp_adjust_tail
> +tprogs-y += xdpsock
> +tprogs-y += xdp_fwd
> +tprogs-y += task_fd_query
> +tprogs-y += xdp_sample_pkts
> +tprogs-y += ibumad
> +tprogs-y += hbm
>
>  # Libbpf dependencies
>  LIBBPF = $(TOOLS_PATH)/lib/bpf/libbpf.a
> @@ -111,7 +109,7 @@ ibumad-objs := bpf_load.o ibumad_user.o $(TRACE_HELPERS)
>  hbm-objs := bpf_load.o hbm.o $(CGROUP_HELPERS)
>
>  # Tell kbuild to always build the programs
> -always := $(hostprogs-y)
> +always := $(tprogs-y)
>  always += sockex1_kern.o
>  always += sockex2_kern.o
>  always += sockex3_kern.o
> @@ -170,21 +168,6 @@ always += ibumad_kern.o
>  always += hbm_out_kern.o
>  always += hbm_edt_kern.o
>
> -KBUILD_HOSTCFLAGS += -I$(objtree)/usr/include
> -KBUILD_HOSTCFLAGS += -I$(srctree)/tools/lib/bpf/
> -KBUILD_HOSTCFLAGS += -I$(srctree)/tools/testing/selftests/bpf/
> -KBUILD_HOSTCFLAGS += -I$(srctree)/tools/lib/ -I$(srctree)/tools/include
> -KBUILD_HOSTCFLAGS += -I$(srctree)/tools/perf
> -
> -HOSTCFLAGS_bpf_load.o += -Wno-unused-variable
> -
> -KBUILD_HOSTLDLIBS              += $(LIBBPF) -lelf
> -HOSTLDLIBS_tracex4             += -lrt
> -HOSTLDLIBS_trace_output        += -lrt
> -HOSTLDLIBS_map_perf_test       += -lrt
> -HOSTLDLIBS_test_overhead       += -lrt
> -HOSTLDLIBS_xdpsock             += -pthread
> -
>  ifeq ($(ARCH), arm)
>  # Strip all except -D__LINUX_ARM_ARCH__ option needed to handle linux
>  # headers when arm instruction set identification is requested.
> @@ -192,9 +175,27 @@ ARM_ARCH_SELECTOR = $(shell echo "$(KBUILD_CFLAGS) " | \
>                     sed 's/[[:blank:]]/\n/g' | sed '/^-D__LINUX_ARM_ARCH__/!d')
>
>  CLANG_EXTRA_CFLAGS := $(ARM_ARCH_SELECTOR)
> -KBUILD_HOSTCFLAGS := $(ARM_ARCH_SELECTOR)
> +TPROGS_CFLAGS += $(ARM_ARCH_SELECTOR)
>  endif
>
> +TPROGS_LDLIBS := $(KBUILD_HOSTLDLIBS)

Please group TPROGS_LDLIBS definition together with the one below,
there doesn't seem to be a reason to split them this way.

But also, it's kind of weird to use host libraries as cross-compiled
libraries as well. Is that intentional?

> +TPROGS_CFLAGS += $(KBUILD_HOSTCFLAGS) $(HOST_EXTRACFLAGS)

Same here, is it right to use HOSTCFLAGS and HOST_EXTRACFLAGS as a
base for cross-compiled cflags?

> +TPROGS_CFLAGS += -I$(objtree)/usr/include
> +TPROGS_CFLAGS += -I$(srctree)/tools/lib/bpf/
> +TPROGS_CFLAGS += -I$(srctree)/tools/testing/selftests/bpf/
> +TPROGS_CFLAGS += -I$(srctree)/tools/lib/
> +TPROGS_CFLAGS += -I$(srctree)/tools/include
> +TPROGS_CFLAGS += -I$(srctree)/tools/perf
> +
> +TPROGCFLAGS_bpf_load.o += -Wno-unused-variable
> +
> +TPROGS_LDLIBS                  += $(LIBBPF) -lelf
> +TPROGLDLIBS_tracex4            += -lrt
> +TPROGLDLIBS_trace_output       += -lrt
> +TPROGLDLIBS_map_perf_test      += -lrt
> +TPROGLDLIBS_test_overhead      += -lrt
> +TPROGLDLIBS_xdpsock            += -pthread
> +
>  # Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
>  #  make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
>  LLC ?= llc
> @@ -285,6 +286,8 @@ $(obj)/hbm_out_kern.o: $(src)/hbm.h $(src)/hbm_kern.h
>  $(obj)/hbm.o: $(src)/hbm.h
>  $(obj)/hbm_edt_kern.o: $(src)/hbm.h $(src)/hbm_kern.h
>
> +-include $(BPF_SAMPLES_PATH)/Makefile.target
> +
>  # asm/sysreg.h - inline assembly used by it is incompatible with llvm.
>  # But, there is no easy way to fix it, so just exclude it since it is
>  # useless for BPF samples.
> --
> 2.17.1
>

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