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

By adding a feature test for bpf_prog_load() 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_prog_load.make.output
test-libbpf-bpf_prog_load.c: In function ‘main’:
test-libbpf-bpf_prog_load.c:6:16: error: implicit declaration of function ‘bpf_prog_load’ [-Werror=implicit-function-declaration]
6 | return bpf_prog_load(0 /* prog_type */, NULL /* prog_name */,
| ^~~~~~~~~~~~~
cc1: all warnings being treated as errors
$

$ objdump -dS /tmp/build/perf/perf | grep '<bpf_prog_load>:' -A20
00000000005b2d70 <bpf_prog_load>:
{
5b2d70: 55 push %rbp
5b2d71: 48 89 ce mov %rcx,%rsi
5b2d74: 4c 89 c8 mov %r9,%rax
5b2d77: 49 89 d2 mov %rdx,%r10
5b2d7a: 4c 89 c2 mov %r8,%rdx
5b2d7d: 48 89 e5 mov %rsp,%rbp
5b2d80: 48 83 ec 18 sub $0x18,%rsp
5b2d84: 64 48 8b 0c 25 28 00 mov %fs:0x28,%rcx
5b2d8b: 00 00
5b2d8d: 48 89 4d f8 mov %rcx,-0x8(%rbp)
5b2d91: 31 c9 xor %ecx,%ecx
return bpf_load_program(prog_type, insns, insn_cnt, license,
5b2d93: 41 8b 49 5c mov 0x5c(%r9),%ecx
5b2d97: 51 push %rcx
5b2d98: 4d 8b 49 60 mov 0x60(%r9),%r9
5b2d9c: 4c 89 d1 mov %r10,%rcx
5b2d9f: 44 8b 40 1c mov 0x1c(%rax),%r8d
5b2da3: e8 f8 aa e5 ff call 40d8a0 <bpf_load_program@plt>
}
$

Signed-off-by: Jiri Olsa <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Ilya Leoshkevich <[e-mail]>
Cc: Sumanth Korikkar <[e-mail]>
Cc: Sven Schnelle <[e-mail]>
Cc: Thomas Richter <[e-mail]>
Cc: Vasily Gorbik <[e-mail]>
Link: http://lore.kernel.org/linux-perf-users/YozLKby7ITEtchC9@krava
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/build/Makefile.feature

···
          clang                          \
          libbpf                         \
          libbpf-btf__load_from_kernel_by_id \
+         libbpf-bpf_prog_load           \
          libpfm4                        \
          libdebuginfod			\
          clang-bpf-co-re

tools/build/feature/Makefile

···
          test-bpf.bin                           \
          test-libbpf.bin                        \
          test-libbpf-btf__load_from_kernel_by_id.bin	\
+         test-libbpf-bpf_prog_load.bin          \
          test-get_cpuid.bin                     \
          test-sdt.bin                           \
          test-cxx.bin                           \
···
 	$(BUILD) -lbpf
 
 $(OUTPUT)test-libbpf-btf__load_from_kernel_by_id.bin:
+	$(BUILD) -lbpf
+
+$(OUTPUT)test-libbpf-bpf_prog_load.bin:
 	$(BUILD) -lbpf
 
 $(OUTPUT)test-sdt.bin:

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

···
+// SPDX-License-Identifier: GPL-2.0
+#include <bpf/bpf.h>
+
+int main(void)
+{
+	return bpf_prog_load(0 /* prog_type */, NULL /* prog_name */,
+			     NULL /* license */, NULL /* insns */,
+			     0 /* insn_cnt */, NULL /* opts */);
+}

tools/perf/Makefile.config

···
           ifeq ($(feature-libbpf-btf__load_from_kernel_by_id), 1)
             CFLAGS += -DHAVE_LIBBPF_BTF__LOAD_FROM_KERNEL_BY_ID
           endif
+          $(call feature_check,libbpf-bpf_prog_load)
+          ifeq ($(feature-libbpf-bpf_prog_load), 1)
+            CFLAGS += -DHAVE_LIBBPF_BPF_PROG_LOAD
+          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
       endif
     endif
 

tools/perf/util/bpf-event.c

···
 }
 #endif
 
-int __weak bpf_prog_load(enum bpf_prog_type prog_type,
-			 const char *prog_name __maybe_unused,
-			 const char *license,
-			 const struct bpf_insn *insns, size_t insn_cnt,
-			 const struct bpf_prog_load_opts *opts)
+#ifndef HAVE_LIBBPF_BPF_PROG_LOAD
+int bpf_prog_load(enum bpf_prog_type prog_type,
+		  const char *prog_name __maybe_unused,
+		  const char *license,
+		  const struct bpf_insn *insns, size_t insn_cnt,
+		  const struct bpf_prog_load_opts *opts)
 {
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
···
 				opts->kern_version, opts->log_buf, opts->log_size);
 #pragma GCC diagnostic pop
 }
+#endif
 
 struct bpf_program * __weak
 bpf_object__next_program(const struct bpf_object *obj, struct bpf_program *prev)