perf build: Stop using __weak bpf_object__next_program() to handle older libbpf versions

By adding a feature test for bpf_object__next_program() and providing a fallback if
it isn't present in older versions of libbpf.

Committer testing:

  $ rpm -q libbpf-devel
  libbpf-devel-0.4.0-2.fc35.x86_64
  $ make -C tools/perf LIBBPF_DYNAMIC=1 O=/tmp/build/perf install-bin
  $ cat /tmp/build/perf/feature/test-libbpf-bpf_object__next_program.make.output
  test-libbpf-bpf_object__next_program.c: In function ‘main’:
  test-libbpf-bpf_object__next_program.c:6:9: error: implicit declaration of function ‘bpf_object__next_program’; did you mean ‘bpf_object__unpin_programs’? [-Werror=implicit-function-declaration]
      6 |         bpf_object__next_program(NULL /* obj */, NULL /* prev */);
        |         ^~~~~~~~~~~~~~~~~~~~~~~~
        |         bpf_object__unpin_programs
  cc1: all warnings being treated as errors
  $
  $ objdump -dS /tmp/build/perf/perf | grep '<bpf_object__next_program>:' -A20
  00000000005b2dc0 <bpf_object__next_program>:
  {
    5b2dc0:	55                   	push   %rbp
    5b2dc1:	48 89 e5             	mov    %rsp,%rbp
    5b2dc4:	48 83 ec 10          	sub    $0x10,%rsp
    5b2dc8:	64 48 8b 04 25 28 00 	mov    %fs:0x28,%rax
    5b2dcf:	00 00
    5b2dd1:	48 89 45 f8          	mov    %rax,-0x8(%rbp)
    5b2dd5:	31 c0                	xor    %eax,%eax
	  return bpf_program__next(prev, obj);
    5b2dd7:	48 8b 45 f8          	mov    -0x8(%rbp),%rax
    5b2ddb:	64 48 2b 04 25 28 00 	sub    %fs:0x28,%rax
    5b2de2:	00 00
    5b2de4:	75 0f                	jne    5b2df5 <bpf_object__next_program+0x35>
  }
    5b2de6:	c9                   	leave
    5b2de7:	49 89 f8             	mov    %rdi,%r8
    5b2dea:	48 89 f7             	mov    %rsi,%rdi
	  return bpf_program__next(prev, obj);
    5b2ded:	4c 89 c6             	mov    %r8,%rsi
    5b2df0:	e9 3b b4 e5 ff       	jmp    40e230 <bpf_program__next@plt>
    $
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Link: http://lore.kernel.org/linux-perf-users/YozLKby7ITEtchC9@kravaSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/build/Makefile.feature

@@ -100,6 +100,7 @@ FEATURE_TESTS_EXTRA :=                  \
          libbpf                         \
          libbpf-btf__load_from_kernel_by_id \
          libbpf-bpf_prog_load           \
+         libbpf-bpf_object__next_program \
          libpfm4                        \
          libdebuginfod			\
          clang-bpf-co-re

tools/build/feature/Makefile

@@ -59,6 +59,7 @@ FILES=                                          \
          test-libbpf.bin                        \
          test-libbpf-btf__load_from_kernel_by_id.bin	\
          test-libbpf-bpf_prog_load.bin          \
+         test-libbpf-bpf_object__next_program.bin \
          test-get_cpuid.bin                     \
          test-sdt.bin                           \
          test-cxx.bin                           \
@@ -295,6 +296,9 @@ $(OUTPUT)test-libbpf-btf__load_from_kernel_by_id.bin:
 $(OUTPUT)test-libbpf-bpf_prog_load.bin:
 	$(BUILD) -lbpf
 
+$(OUTPUT)test-libbpf-bpf_object__next_program.bin:
+	$(BUILD) -lbpf
+
 $(OUTPUT)test-sdt.bin:
 	$(BUILD)
 

tools/build/feature/test-libbpf-bpf_object__next_program.c

+// SPDX-License-Identifier: GPL-2.0
+#include <bpf/libbpf.h>
+
+int main(void)
+{
+	bpf_object__next_program(NULL /* obj */, NULL /* prev */);
+	return 0;
+}

tools/perf/Makefile.config

@@ -577,12 +577,17 @@ ifndef NO_LIBELF
           ifeq ($(feature-libbpf-bpf_prog_load), 1)
             CFLAGS += -DHAVE_LIBBPF_BPF_PROG_LOAD
           endif
+          $(call feature_check,libbpf-bpf_object__next_program)
+          ifeq ($(feature-libbpf-bpf_object__next_program), 1)
+            CFLAGS += -DHAVE_LIBBPF_BPF_OBJECT__NEXT_PROGRAM
+          endif
         else
           dummy := $(error Error: No libbpf devel library found, please install libbpf-devel);
         endif
       else
 	CFLAGS += -DHAVE_LIBBPF_BTF__LOAD_FROM_KERNEL_BY_ID
         CFLAGS += -DHAVE_LIBBPF_BPF_PROG_LOAD
+        CFLAGS += -DHAVE_LIBBPF_BPF_OBJECT__NEXT_PROGRAM
       endif
     endif
 

tools/perf/util/bpf-event.c

@@ -50,7 +50,8 @@ int bpf_prog_load(enum bpf_prog_type prog_type,
 }
 #endif
 
-struct bpf_program * __weak
+#ifndef HAVE_LIBBPF_BPF_OBJECT__NEXT_PROGRAM
+struct bpf_program *
 bpf_object__next_program(const struct bpf_object *obj, struct bpf_program *prev)
 {
 #pragma GCC diagnostic push
@@ -58,6 +59,7 @@ bpf_object__next_program(const struct bpf_object *obj, struct bpf_program *prev)
 	return bpf_program__next(prev, obj);
 #pragma GCC diagnostic pop
 }
+#endif
 
 struct bpf_map * __weak
 bpf_object__next_map(const struct bpf_object *obj, const struct bpf_map *prev)