On Wed, Jul 13, 2022 at 10:48 AM Quentin Monnet [off-list ref] wrote:

On 12/07/2022 15:58, Benjamin Tissoires wrote:

[...]

quoted

diff --git a/drivers/hid/bpf/entrypoints/Makefile b/drivers/hid/bpf/entrypoints/Makefile
new file mode 100644
index 000000000000..dd60a460c6c4
--- /dev/null
+++ b/drivers/hid/bpf/entrypoints/Makefile

@@ -0,0 +1,88 @@
+# SPDX-License-Identifier: GPL-2.0
+OUTPUT := .output
+abs_out := $(abspath $(OUTPUT))
+
+CLANG ?= clang
+LLC ?= llc
+LLVM_STRIP ?= llvm-strip
+
+TOOLS_PATH := $(abspath ../../../../tools)
+BPFTOOL_SRC := $(TOOLS_PATH)/bpf/bpftool
+BPFTOOL_OUTPUT := $(abs_out)/bpftool
+DEFAULT_BPFTOOL := $(OUTPUT)/sbin/bpftool
+BPFTOOL ?= $(DEFAULT_BPFTOOL)
+
+LIBBPF_SRC := $(TOOLS_PATH)/lib/bpf
+LIBBPF_OUTPUT := $(abs_out)/libbpf
+LIBBPF_DESTDIR := $(LIBBPF_OUTPUT)
+LIBBPF_INCLUDE := $(LIBBPF_DESTDIR)/include
+BPFOBJ := $(LIBBPF_OUTPUT)/libbpf.a
+
+INCLUDES := -I$(OUTPUT) -I$(LIBBPF_INCLUDE) -I$(TOOLS_PATH)/include/uapi
+CFLAGS := -g -Wall
+
+VMLINUX_BTF_PATHS ?= $(if $(O),$(O)/vmlinux)                         \
+                  $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)    \
+                  ../../../../vmlinux                                \
+                  /sys/kernel/btf/vmlinux                            \
+                  /boot/vmlinux-$(shell uname -r)
+VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
+ifeq ($(VMLINUX_BTF),)
+$(error Cannot find a vmlinux for VMLINUX_BTF at any of "$(VMLINUX_BTF_PATHS)")
+endif
+
+ifeq ($(V),1)
+Q =
+msg =
+else
+Q = @
+msg = @printf '  %-8s %s%s\n' "$(1)" "$(notdir $(2))" "$(if $(3), $(3))";
+MAKEFLAGS += --no-print-directory
+submake_extras := feature_display=0
+endif
+
+.DELETE_ON_ERROR:
+
+.PHONY: all clean
+
+all: entrypoints.lskel.h
+
+clean:
+     $(call msg,CLEAN)
+     $(Q)rm -rf $(OUTPUT) entrypoints
+
+entrypoints.lskel.h: $(OUTPUT)/entrypoints.bpf.o | $(BPFTOOL)
+     $(call msg,GEN-SKEL,$@)
+     $(Q)$(BPFTOOL) gen skeleton -L $< > $@
+
+
+$(OUTPUT)/entrypoints.bpf.o: entrypoints.bpf.c $(OUTPUT)/vmlinux.h $(BPFOBJ) | $(OUTPUT)
+     $(call msg,BPF,$@)
+     $(Q)$(CLANG) -g -O2 -target bpf $(INCLUDES)                           \
+              -c $(filter %.c,$^) -o $@ &&                                 \
+     $(LLVM_STRIP) -g $@
+
+$(OUTPUT)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL) | $(INCLUDE_DIR)
+ifeq ($(VMLINUX_H),)
+     $(call msg,GEN,,$@)
+     $(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@
+else
+     $(call msg,CP,,$@)
+     $(Q)cp "$(VMLINUX_H)" $@
+endif
+
+$(OUTPUT) $(LIBBPF_OUTPUT) $(BPFTOOL_OUTPUT):
+     $(call msg,MKDIR,$@)
+     $(Q)mkdir -p $@
+
+$(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OUTPUT)
+     $(Q)$(MAKE) $(submake_extras) -C $(LIBBPF_SRC)                         \
+                 OUTPUT=$(abspath $(dir $@))/ prefix=                       \
+                 DESTDIR=$(LIBBPF_DESTDIR) $(abspath $@) install_headers
+
+$(DEFAULT_BPFTOOL): $(BPFOBJ) | $(BPFTOOL_OUTPUT)
+     $(Q)$(MAKE) $(submake_extras) -C $(BPFTOOL_SRC)                        \
+                 OUTPUT=$(BPFTOOL_OUTPUT)/                                  \
+                 LIBBPF_OUTPUT=$(LIBBPF_OUTPUT)/                            \
+                 LIBBPF_DESTDIR=$(LIBBPF_DESTDIR)/                          \
+                 prefix= DESTDIR=$(abs_out)/ install-bin

Hi Benjamin,

Note that, at other locations where bpftool is needed to generate the
vmlinux.h or the skeletons, there is some work in progress to use only
the "bootstrap" version of bpftool (the intermediary bpftool binary used
to generate skeletons required for the final bpftool binary) [0]. This
is enough to generate these objects, it makes compiling the bpftool
binary faster, and solves some issues related to cross-compilation. It's
probably worth exploring in your case (or as a follow-up) as well.

Hi Quentin,

Indeed, I applied a similar patch to [1] (the 3/3 in the series you
mentioned) and I have the exact same light skeleton.
I have stashed the changes locally for a future revision (I doubt
everything will go through in this version ;-P ).

Cheers,
Benjamin

Quentin

[0]
https://lore.kernel.org/all/20220712030813.865410-1-pulehui@huawei.com/t/#u (local)

[1] https://lore.kernel.org/all/20220712030813.865410-4-pulehui@huawei.com/ (local)