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authorArnaldo Carvalho de Melo <acme@redhat.com>2022-05-19 21:25:12 -0300
committerArnaldo Carvalho de Melo <acme@redhat.com>2022-05-20 09:45:41 -0300
commit0ae065a5d265bc5ada13e350015458e0c5e5c351 (patch)
treea12c79784a5cd0b0eadd5c570d5d5b395b19c057 /tools/build
parent3d7285a335edaf23b699e87c528cf0b0070e3293 (diff)
perf build: Fix check for btf__load_from_kernel_by_id() in libbpf
Avi Kivity reported a problem where the __weak btf__load_from_kernel_by_id() in tools/perf/util/bpf-event.c was being used and it called btf__get_from_id() in tools/lib/bpf/btf.c that in turn called back to btf__load_from_kernel_by_id(), resulting in an endless loop. Fix this by adding a feature test to check if btf__load_from_kernel_by_id() is available when building perf with LIBBPF_DYNAMIC=1, and if not then provide the fallback to the old btf__get_from_id(), that doesn't call back to btf__load_from_kernel_by_id() since at that time it didn't exist at all. Tested on Fedora 35 where we have libbpf-devel 0.4.0 with LIBBPF_DYNAMIC where we don't have btf__load_from_kernel_by_id() and thus its feature test fail, not defining HAVE_LIBBPF_BTF__LOAD_FROM_KERNEL_BY_ID: $ cat /tmp/build/perf-urgent/feature/test-libbpf-btf__load_from_kernel_by_id.make.output test-libbpf-btf__load_from_kernel_by_id.c: In function ‘main’: test-libbpf-btf__load_from_kernel_by_id.c:6:16: error: implicit declaration of function ‘btf__load_from_kernel_by_id’ [-Werror=implicit-function-declaration] 6 | return btf__load_from_kernel_by_id(20151128, NULL); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~ cc1: all warnings being treated as errors $ $ nm /tmp/build/perf-urgent/perf | grep btf__load_from_kernel_by_id 00000000005ba180 T btf__load_from_kernel_by_id $ $ objdump --disassemble=btf__load_from_kernel_by_id -S /tmp/build/perf-urgent/perf /tmp/build/perf-urgent/perf: file format elf64-x86-64 <SNIP> 00000000005ba180 <btf__load_from_kernel_by_id>: #include "record.h" #include "util/synthetic-events.h" #ifndef HAVE_LIBBPF_BTF__LOAD_FROM_KERNEL_BY_ID struct btf *btf__load_from_kernel_by_id(__u32 id) { 5ba180: 55 push %rbp 5ba181: 48 89 e5 mov %rsp,%rbp 5ba184: 48 83 ec 10 sub $0x10,%rsp 5ba188: 64 48 8b 04 25 28 00 mov %fs:0x28,%rax 5ba18f: 00 00 5ba191: 48 89 45 f8 mov %rax,-0x8(%rbp) 5ba195: 31 c0 xor %eax,%eax struct btf *btf; #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Wdeprecated-declarations" int err = btf__get_from_id(id, &btf); 5ba197: 48 8d 75 f0 lea -0x10(%rbp),%rsi 5ba19b: e8 a0 57 e5 ff call 40f940 <btf__get_from_id@plt> 5ba1a0: 89 c2 mov %eax,%edx #pragma GCC diagnostic pop return err ? ERR_PTR(err) : btf; 5ba1a2: 48 98 cltq 5ba1a4: 85 d2 test %edx,%edx 5ba1a6: 48 0f 44 45 f0 cmove -0x10(%rbp),%rax } <SNIP> Fixes: 218e7b775d368f38 ("perf bpf: Provide a weak btf__load_from_kernel_by_id() for older libbpf versions") Reported-by: Avi Kivity <avi@scylladb.com> Link: https://lore.kernel.org/linux-perf-users/f0add43b-3de5-20c5-22c4-70aff4af959f@scylladb.com Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Ian Rogers <irogers@google.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Namhyung Kim <namhyung@kernel.org> Link: https://lore.kernel.org/linux-perf-users/YobjjFOblY4Xvwo7@kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/build')
-rw-r--r--tools/build/Makefile.feature1
-rw-r--r--tools/build/feature/Makefile4
-rw-r--r--tools/build/feature/test-libbpf-btf__load_from_kernel_by_id.c7
3 files changed, 12 insertions, 0 deletions
diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
index ae61f464043a..c6a48d0ef9ff 100644
--- a/tools/build/Makefile.feature
+++ b/tools/build/Makefile.feature
@@ -98,6 +98,7 @@ FEATURE_TESTS_EXTRA := \
llvm-version \
clang \
libbpf \
+ libbpf-btf__load_from_kernel_by_id \
libpfm4 \
libdebuginfod \
clang-bpf-co-re
diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index de66e1cc0734..cb4a2a4fa2e4 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -57,6 +57,7 @@ FILES= \
test-lzma.bin \
test-bpf.bin \
test-libbpf.bin \
+ test-libbpf-btf__load_from_kernel_by_id.bin \
test-get_cpuid.bin \
test-sdt.bin \
test-cxx.bin \
@@ -287,6 +288,9 @@ $(OUTPUT)test-bpf.bin:
$(OUTPUT)test-libbpf.bin:
$(BUILD) -lbpf
+$(OUTPUT)test-libbpf-btf__load_from_kernel_by_id.bin:
+ $(BUILD) -lbpf
+
$(OUTPUT)test-sdt.bin:
$(BUILD)
diff --git a/tools/build/feature/test-libbpf-btf__load_from_kernel_by_id.c b/tools/build/feature/test-libbpf-btf__load_from_kernel_by_id.c
new file mode 100644
index 000000000000..f7c084428735
--- /dev/null
+++ b/tools/build/feature/test-libbpf-btf__load_from_kernel_by_id.c
@@ -0,0 +1,7 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <bpf/libbpf.h>
+
+int main(void)
+{
+ return btf__load_from_kernel_by_id(20151128, NULL);
+}