bpftool: Fix install for libbpf's internal header(s)

We recently updated bpftool's Makefile to make it install the headers
from libbpf, instead of pulling them directly from libbpf's directory.
There is also an additional header, internal to libbpf, that needs be
installed. The way that bpftool's Makefile installs that particular
header is currently correct, but would break if we were to modify
$(LIBBPF_INTERNAL_HDRS) to make it point to more than one header.

Use a static pattern rule instead, so that the Makefile can withstand
the addition of other headers to install.

The objective is simply to make the Makefile more robust. It should
_not_ be read as an invitation to import more internal headers from
libbpf into bpftool.

Fixes: f012ade10b34 ("bpftool: Install libbpf headers instead of including the dir")
Reported-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20211009210341.6291-2-quentin@isovalent.com

diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index 9c2d13c513f0eb6dd781b5ed3a7f7f1fba36890b..646fd40b32533bd53d21da030df129cbafad012d 100644 (file)
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -14,7 +14,7 @@ else
   Q = @
 endif
 
-BPF_DIR = $(srctree)/tools/lib/bpf/
+BPF_DIR = $(srctree)/tools/lib/bpf
 
 ifneq ($(OUTPUT),)
   _OUTPUT := $(OUTPUT)
@@ -25,6 +25,7 @@ BOOTSTRAP_OUTPUT := $(_OUTPUT)/bootstrap/
 LIBBPF_OUTPUT := $(_OUTPUT)/libbpf/
 LIBBPF_DESTDIR := $(LIBBPF_OUTPUT)
 LIBBPF_INCLUDE := $(LIBBPF_DESTDIR)/include
+LIBBPF_HDRS_DIR := $(LIBBPF_INCLUDE)/bpf
 
 LIBBPF = $(LIBBPF_OUTPUT)libbpf.a
 LIBBPF_BOOTSTRAP_OUTPUT = $(BOOTSTRAP_OUTPUT)libbpf/
@@ -32,7 +33,7 @@ LIBBPF_BOOTSTRAP = $(LIBBPF_BOOTSTRAP_OUTPUT)libbpf.a
 
 # We need to copy nlattr.h which is not otherwise exported by libbpf, but still
 # required by bpftool.
-LIBBPF_INTERNAL_HDRS := nlattr.h
+LIBBPF_INTERNAL_HDRS := $(addprefix $(LIBBPF_HDRS_DIR)/,nlattr.h)
 
 ifeq ($(BPFTOOL_VERSION),)
 BPFTOOL_VERSION := $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
@@ -45,10 +46,9 @@ $(LIBBPF): FORCE | $(LIBBPF_OUTPUT)
        $(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_OUTPUT) \
                DESTDIR=$(LIBBPF_DESTDIR) prefix= $(LIBBPF) install_headers
 
-$(LIBBPF_INCLUDE)/bpf/$(LIBBPF_INTERNAL_HDRS): \
-               $(addprefix $(BPF_DIR),$(LIBBPF_INTERNAL_HDRS)) $(LIBBPF)
-       $(call QUIET_INSTALL, bpf/$(notdir $@))
-       $(Q)install -m 644 -t $(LIBBPF_INCLUDE)/bpf/ $(BPF_DIR)$(notdir $@)
+$(LIBBPF_INTERNAL_HDRS): $(LIBBPF_HDRS_DIR)/%.h: $(BPF_DIR)/%.h $(LIBBPF)
+       $(call QUIET_INSTALL, $@)
+       $(Q)install -m 644 -t $(LIBBPF_HDRS_DIR) $<
 
 $(LIBBPF_BOOTSTRAP): FORCE | $(LIBBPF_BOOTSTRAP_OUTPUT)
        $(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_BOOTSTRAP_OUTPUT) \
@@ -150,7 +150,7 @@ BOOTSTRAP_OBJS = $(addprefix $(BOOTSTRAP_OUTPUT),main.o common.o json_writer.o g
 $(BOOTSTRAP_OBJS): $(LIBBPF_BOOTSTRAP)
 
 OBJS = $(patsubst %.c,$(OUTPUT)%.o,$(SRCS)) $(OUTPUT)disasm.o
-$(OBJS): $(LIBBPF) $(LIBBPF_INCLUDE)/bpf/$(LIBBPF_INTERNAL_HDRS)
+$(OBJS): $(LIBBPF) $(LIBBPF_INTERNAL_HDRS)
 
 VMLINUX_BTF_PATHS ?= $(if $(O),$(O)/vmlinux)                           \
                     $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)    \