perf bpf: Fix build with libbpf 0.7.0 by checking if bpf_program__set_insns() is available

During the transition to libbpf 1.0 some functions that perf used were
deprecated and finally removed from libbpf, so bpf_program__set_insns()
was introduced for perf to continue to use its bpf loader.

But when build with LIBBPF_DYNAMIC=1 we now need to check if that
function is available so that perf can build with older libbpf versions,
even if the end result is emitting a warning to the user that the use
of the perf BPF loader requires a newer libbpf, since bpf_program__set_insns()
touches libbpf objects internal state.

This affects only 'perf trace' when using bpf C code or pre-compiled
bytecode as an event.

Noticed on RHEL9, that has libbpf 0.7.0, where bpf_program__set_insns()
isn't available.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/build/Makefile.feature

@@ -103,6 +103,7 @@ FEATURE_TESTS_EXTRA :=                  \
          libbpf-bpf_prog_load           \
          libbpf-bpf_object__next_program \
          libbpf-bpf_object__next_map    \
+         libbpf-bpf_program__set_insns  \
          libbpf-bpf_create_map		\
          libpfm4                        \
          libdebuginfod			\

tools/build/feature/Makefile

@@ -63,6 +63,7 @@ FILES=                                          \
          test-libbpf-bpf_map_create.bin		\
          test-libbpf-bpf_object__next_program.bin \
          test-libbpf-bpf_object__next_map.bin   \
+         test-libbpf-bpf_program__set_insns.bin	\
          test-libbpf-btf__raw_data.bin          \
          test-get_cpuid.bin                     \
          test-sdt.bin                           \
@@ -316,6 +317,9 @@ $(OUTPUT)test-libbpf-bpf_object__next_program.bin:
 $(OUTPUT)test-libbpf-bpf_object__next_map.bin:
 	$(BUILD) -lbpf
 
+$(OUTPUT)test-libbpf-bpf_program__set_insns.bin:
+	$(BUILD) -lbpf
+
 $(OUTPUT)test-libbpf-btf__raw_data.bin:
 	$(BUILD) -lbpf
 

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

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

tools/perf/Makefile.config

@@ -588,6 +588,10 @@ ifndef NO_LIBELF
           ifeq ($(feature-libbpf-bpf_object__next_map), 1)
             CFLAGS += -DHAVE_LIBBPF_BPF_OBJECT__NEXT_MAP
           endif
+          $(call feature_check,libbpf-bpf_program__set_insns)
+          ifeq ($(feature-libbpf-bpf_program__set_insns), 1)
+            CFLAGS += -DHAVE_LIBBPF_BPF_PROGRAM__SET_INSNS
+          endif
           $(call feature_check,libbpf-btf__raw_data)
           ifeq ($(feature-libbpf-btf__raw_data), 1)
             CFLAGS += -DHAVE_LIBBPF_BTF__RAW_DATA
@@ -604,6 +608,7 @@ ifndef NO_LIBELF
         CFLAGS += -DHAVE_LIBBPF_BPF_PROG_LOAD
         CFLAGS += -DHAVE_LIBBPF_BPF_OBJECT__NEXT_PROGRAM
         CFLAGS += -DHAVE_LIBBPF_BPF_OBJECT__NEXT_MAP
+        CFLAGS += -DHAVE_LIBBPF_BPF_PROGRAM__SET_INSNS
         CFLAGS += -DHAVE_LIBBPF_BTF__RAW_DATA
         CFLAGS += -DHAVE_LIBBPF_BPF_MAP_CREATE
       endif

tools/perf/util/bpf-loader.c

@@ -36,6 +36,24 @@
 
 #include <internal/xyarray.h>
 
+#ifndef HAVE_LIBBPF_BPF_PROGRAM__SET_INSNS
+int bpf_program__set_insns(struct bpf_program *prog __maybe_unused,
+			   struct bpf_insn *new_insns __maybe_unused, size_t new_insn_cnt __maybe_unused)
+{
+	pr_err("%s: not support, update libbpf\n", __func__);
+	return -ENOTSUP;
+}
+
+int libbpf_register_prog_handler(const char *sec __maybe_unused,
+                                 enum bpf_prog_type prog_type __maybe_unused,
+                                 enum bpf_attach_type exp_attach_type __maybe_unused,
+                                 const struct libbpf_prog_handler_opts *opts __maybe_unused)
+{
+	pr_err("%s: not support, update libbpf\n", __func__);
+	return -ENOTSUP;
+}
+#endif
+
 /* temporarily disable libbpf deprecation warnings */
 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"