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

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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: 384b6b3bbf (samples: bpf: Add vmlinux.h generation support)
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210928054608.1799021-1-memxor@gmail.com
This commit is contained in:
Kumar Kartikeya Dwivedi 2021-09-28 11:16:08 +05:30 committed by Andrii Nakryiko
parent 4ccb9f03fe
commit 571fa247ab
2 changed files with 8 additions and 14 deletions
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17
samples/bpf/Makefile
View File

@ -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

5
samples/bpf/xdp_redirect_map_multi.bpf.c
View File

@ -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));