[FYI PATCH 1/1] perf build: Stop using __weak bpf_map_create() to handle older libbpf versions
From: Arnaldo Carvalho de Melo
Date: Thu May 26 2022 - 11:07:52 EST
I'm carrying this one in my perf/core branch to fix the build with latest torvalds/master.
- Arnaldo
----
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 <andrii@xxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Ian Rogers <irogers@xxxxxxxxxx>
Cc: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Song Liu <songliubraving@xxxxxx>
Cc: Sumanth Korikkar <sumanthk@xxxxxxxxxxxxx>
Cc: Sven Schnelle <svens@xxxxxxxxxxxxx>
Cc: Thomas Richter <tmricht@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Link: http://lore.kernel.org/linux-perf-users/
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/build/Makefile.feature | 1 +
tools/build/feature/Makefile | 4 ++++
tools/build/feature/test-libbpf-bpf_map_create.c | 8 ++++++++
tools/perf/Makefile.config | 5 +++++
tools/perf/util/bpf_counter.c | 6 +++++-
5 files changed, 23 insertions(+), 1 deletion(-)
create mode 100644 tools/build/feature/test-libbpf-bpf_map_create.c
diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
index 34cf2bff72ca20e5..888a0421d43b9606 100644
--- a/tools/build/Makefile.feature
+++ b/tools/build/Makefile.feature
@@ -102,6 +102,7 @@ FEATURE_TESTS_EXTRA := \
libbpf-bpf_prog_load \
libbpf-bpf_object__next_program \
libbpf-bpf_object__next_map \
+ libbpf-bpf_create_map \
libpfm4 \
libdebuginfod \
clang-bpf-co-re
diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index 5b31a6d063d731c2..7c2a17e23c30aca0 100644
--- a/tools/build/feature/Makefile
+++ b/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_map_create.bin \
test-libbpf-bpf_object__next_program.bin \
test-libbpf-bpf_object__next_map.bin \
test-libbpf-btf__raw_data.bin \
@@ -298,6 +299,9 @@ $(OUTPUT)test-libbpf-btf__load_from_kernel_by_id.bin:
$(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:
$(BUILD) -lbpf
diff --git a/tools/build/feature/test-libbpf-bpf_map_create.c b/tools/build/feature/test-libbpf-bpf_map_create.c
new file mode 100644
index 0000000000000000..b9f550e332c8fdab
--- /dev/null
+++ b/tools/build/feature/test-libbpf-bpf_map_create.c
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <bpf/bpf.h>
+
+int main(void)
+{
+ return bpf_map_create(0 /* map_type */, NULL /* map_name */, 0, /* key_size */,
+ 0 /* value_size */, 0 /* max_entries */, NULL /* opts */);
+}
diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index c27fd00865c593b4..73e0762092feba30 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -589,6 +589,10 @@ ifndef NO_LIBELF
ifeq ($(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
@@ -598,6 +602,7 @@ ifndef NO_LIBELF
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
diff --git a/tools/perf/util/bpf_counter.c b/tools/perf/util/bpf_counter.c
index d4931f54e1dd38ea..ef1c15e4aeba5ed4 100644
--- a/tools/perf/util/bpf_counter.c
+++ b/tools/perf/util/bpf_counter.c
@@ -312,7 +312,10 @@ static bool bperf_attr_map_compatible(int attr_map_fd)
(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,
@@ -325,6 +328,7 @@ bpf_map_create(enum bpf_map_type map_type,
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)
{
--
2.35.1