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

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

This also fixes the build with torvalds/master at this point:

$ git log --oneline -5 torvalds/master
babf0bb978e3c9fc (torvalds/master) Merge tag 'xfs-5.19-for-linus' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux
e375780b631a5fc2 Merge tag 'fsnotify_for_v5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs
8b728edc5be16179 Merge tag 'fs_for_v5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs
3f306ea2e18568f6 Merge tag 'dma-mapping-5.19-2022-05-25' of git://git.infradead.org/users/hch/dma-mapping
fbe86daca0ba878b Merge tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi
$

Coping with:

$ git log --oneline -2 d16495a982324f75
d16495a982324f75 libbpf: remove bpf_create_map*() APIs
e2371b1632b1c61c libbpf: start 1.0 development cycle
$

As the __weak function fails to build as it calls the now removed
bpf_create_map() API.

Testing:

$ rpm -q libbpf-devel
libbpf-devel-0.4.0-2.fc35.x86_64
$
$ make -C tools/perf BUILD_BPF_SKEL=1 LIBBPF_DYNAMIC=1 O=/tmp/build/perf install-bin
$ cat /tmp/build/perf/feature/test-libbpf-bpf_map_create.make.output
test-libbpf-bpf_map_create.c: In function ‘main’:
test-libbpf-bpf_map_create.c:6:16: error: implicit declaration of function ‘bpf_map_create’; did you mean ‘bpf_map_freeze’? [-Werror=implicit-function-declaration]
6 | return bpf_map_create(0 /* map_type */, NULL /* map_name */, 0, /* key_size */,
| ^~~~~~~~~~~~~~
| bpf_map_freeze
test-libbpf-bpf_map_create.c:6:87: error: expected expression before ‘,’ token
6 | return bpf_map_create(0 /* map_type */, NULL /* map_name */, 0, /* key_size */,
| ^
cc1: all warnings being treated as errors
$
$ objdump -dS /tmp/build/perf/perf | grep '<bpf_map_create>:' -A20
000000000058b290 <bpf_map_create>:
{
58b290: 55 push %rbp
58b291: 48 89 e5 mov %rsp,%rbp
58b294: 48 83 ec 10 sub $0x10,%rsp
58b298: 64 48 8b 04 25 28 00 mov %fs:0x28,%rax
58b29f: 00 00
58b2a1: 48 89 45 f8 mov %rax,-0x8(%rbp)
58b2a5: 31 c0 xor %eax,%eax
return bpf_create_map(map_type, key_size, value_size, max_entries, 0);
58b2a7: 48 8b 45 f8 mov -0x8(%rbp),%rax
58b2ab: 64 48 2b 04 25 28 00 sub %fs:0x28,%rax
58b2b2: 00 00
58b2b4: 75 10 jne 58b2c6 <bpf_map_create+0x36>
}
58b2b6: c9 leave
58b2b7: 89 d6 mov %edx,%esi
58b2b9: 89 ca mov %ecx,%edx
58b2bb: 44 89 c1 mov %r8d,%ecx
return bpf_create_map(map_type, key_size, value_size, max_entries, 0);
58b2be: 45 31 c0 xor %r8d,%r8d
$

Cc: Andrii Nakryiko <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Ilya Leoshkevich <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Song Liu <[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/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/build/Makefile.feature

···
          libbpf-bpf_prog_load           \
          libbpf-bpf_object__next_program \
          libbpf-bpf_object__next_map    \
+         libbpf-bpf_create_map		\
          libpfm4                        \
          libdebuginfod			\
          clang-bpf-co-re

tools/build/feature/Makefile

···
          test-libbpf.bin                        \
          test-libbpf-btf__load_from_kernel_by_id.bin	\
          test-libbpf-bpf_prog_load.bin          \
+         test-libbpf-bpf_map_create.bin		\
          test-libbpf-bpf_object__next_program.bin \
          test-libbpf-bpf_object__next_map.bin   \
          test-libbpf-btf__raw_data.bin          \
···
 	$(BUILD) -lbpf
 
 $(OUTPUT)test-libbpf-bpf_prog_load.bin:
+	$(BUILD) -lbpf
+
+$(OUTPUT)test-libbpf-bpf_map_create.bin:
 	$(BUILD) -lbpf
 
 $(OUTPUT)test-libbpf-bpf_object__next_program.bin:

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

···
+// SPDX-License-Identifier: GPL-2.0
+#include <bpf/bpf.h>
+
+int main(void)
+{
+	return bpf_map_create(0 /* map_type */, NULL /* map_name */, 0, /* key_size */,
+			      0 /* value_size */, 0 /* max_entries */, NULL /* opts */);
+}

tools/perf/Makefile.config

···
           ifeq ($(feature-libbpf-btf__raw_data), 1)
             CFLAGS += -DHAVE_LIBBPF_BTF__RAW_DATA
           endif
+          $(call feature_check,libbpf-bpf_map_create)
+          ifeq ($(feature-libbpf-bpf_map_create), 1)
+            CFLAGS += -DHAVE_LIBBPF_BPF_MAP_CREATE
+          endif
         else
           dummy := $(error Error: No libbpf devel library found, please install libbpf-devel);
         endif
···
         CFLAGS += -DHAVE_LIBBPF_BPF_OBJECT__NEXT_PROGRAM
         CFLAGS += -DHAVE_LIBBPF_BPF_OBJECT__NEXT_MAP
         CFLAGS += -DHAVE_LIBBPF_BTF__RAW_DATA
+        CFLAGS += -DHAVE_LIBBPF_BPF_MAP_CREATE
       endif
     endif
 

tools/perf/util/bpf_counter.c

···
 		(map_info.value_size == sizeof(struct perf_event_attr_map_entry));
 }
 
-int __weak
+#ifndef HAVE_LIBBPF_BPF_MAP_CREATE
+LIBBPF_API int bpf_create_map(enum bpf_map_type map_type, int key_size,
+                              int value_size, int max_entries, __u32 map_flags);
+int
 bpf_map_create(enum bpf_map_type map_type,
 	       const char *map_name __maybe_unused,
 	       __u32 key_size,
···
 	return bpf_create_map(map_type, key_size, value_size, max_entries, 0);
 #pragma GCC diagnostic pop
 }
+#endif
 
 static int bperf_lock_attr_map(struct target *target)
 {