Commit 571fa247 authored by Kumar Kartikeya Dwivedi's avatar Kumar Kartikeya Dwivedi Committed by Andrii Nakryiko
Browse files

samples: bpf: Fix vmlinux.h generation for XDP samples 



Generate vmlinux.h only from the in-tree vmlinux, and remove enum
declarations that would cause a build failure in case of version
mismatches.

There are now two options when building the samples:
1. Compile the kernel to use in-tree vmlinux for vmlinux.h
2. Override VMLINUX_BTF for samples using something like this:
   make VMLINUX_BTF=/sys/kernel/btf/vmlinux -C samples/bpf

This change was tested with relative builds, e.g. cases like:
 * make O=build -C samples/bpf
 * make KBUILD_OUTPUT=build -C samples/bpf
 * make -C samples/bpf
 * cd samples/bpf && make

When a suitable VMLINUX_BTF is not found, the following message is
printed:
/home/kkd/src/linux/samples/bpf/Makefile:333: *** Cannot find a vmlinux
for VMLINUX_BTF at any of "  ./vmlinux", build the kernel or set
VMLINUX_BTF variable.  Stop.

Fixes: 384b6b3b (samples: bpf: Add vmlinux.h generation support)
Signed-off-by: default avatarKumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarToke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210928054608.1799021-1-memxor@gmail.com
parent 4ccb9f03

samples/bpf/Makefile

+8 −9
Original line number Diff line number Diff line
@@ -322,17 +322,11 @@ $(obj)/hbm_edt_kern.o: $(src)/hbm.h $(src)/hbm_kern.h 


-include $(BPF_SAMPLES_PATH)/Makefile.target



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_PATHS ?= $(abspath $(if $(O),$(O)/vmlinux))				\

		     $(abspath $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux))	\

		     $(abspath ./vmlinux)

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



$(obj)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)

ifeq ($(VMLINUX_H),)

	$(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@
@@ -340,6 +334,11 @@ else 
	$(Q)cp "$(VMLINUX_H)" $@

endif



ifeq ($(VMLINUX_BTF),)

	$(error Cannot find a vmlinux for VMLINUX_BTF at any of "$(VMLINUX_BTF_PATHS)",\

		build the kernel or set VMLINUX_BTF variable)

endif



clean-files += vmlinux.h



# Get Clang's default includes on this system, as opposed to those seen by

samples/bpf/xdp_redirect_map_multi.bpf.c

+0 −5
Original line number Diff line number Diff line
@@ -5,11 +5,6 @@ 
#include "xdp_sample.bpf.h"

#include "xdp_sample_shared.h"



enum {

	BPF_F_BROADCAST		= (1ULL << 3),

	BPF_F_EXCLUDE_INGRESS	= (1ULL << 4),

};



struct {

	__uint(type, BPF_MAP_TYPE_DEVMAP_HASH);

	__uint(key_size, sizeof(int));