From 1d0654b7fdc5431b85035f6e76b4bc57679575d8 Mon Sep 17 00:00:00 2001 From: Blake Jones Date: Thu, 12 Jun 2025 12:49:35 -0700 Subject: [PATCH] perf build: detect support for libbpf's emit_strings option This creates a config option that detects libbpf's ability to display character arrays as strings, which was just added to the BPF tree (https://git.kernel.org/bpf/bpf-next/c/87c9c79a02b4). To test this change, I built perf (from later in this patch set) with: - static libbpf (default, using source from kernel tree) - dynamic libbpf (LIBBPF_DYNAMIC=1 LIBBPF_INCLUDE=/usr/local/include) For both the static and dynamic versions, I used headers with and without the ".emit_strings" option. I verified that of the four resulting binaries, the two with ".emit_strings" would successfully record BPF_METADATA events, and the two without wouldn't. All four binaries would successfully display BPF_METADATA events, because the relevant bit of libbpf code is only used during "perf record". Signed-off-by: Blake Jones Link: https://lore.kernel.org/r/20250612194939.162730-2-blakejones@google.com Signed-off-by: Namhyung Kim --- tools/build/Makefile.feature | 1 + tools/build/feature/Makefile | 4 ++++ tools/build/feature/test-libbpf-strings.c | 10 ++++++++++ tools/perf/Documentation/perf-check.txt | 1 + tools/perf/Makefile.config | 8 ++++++++ tools/perf/builtin-check.c | 1 + 6 files changed, 25 insertions(+) create mode 100644 tools/build/feature/test-libbpf-strings.c diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature index 3a1fddd38db0..2e5f4c8b6547 100644 --- a/tools/build/Makefile.feature +++ b/tools/build/Makefile.feature @@ -126,6 +126,7 @@ FEATURE_TESTS_EXTRA := \ llvm \ clang \ libbpf \ + libbpf-strings \ libpfm4 \ libdebuginfod \ clang-bpf-co-re \ diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile index 4aa166d3eab6..0c4e541ed56e 100644 --- a/tools/build/feature/Makefile +++ b/tools/build/feature/Makefile @@ -59,6 +59,7 @@ FILES= \ test-lzma.bin \ test-bpf.bin \ test-libbpf.bin \ + test-libbpf-strings.bin \ test-get_cpuid.bin \ test-sdt.bin \ test-cxx.bin \ @@ -339,6 +340,9 @@ $(OUTPUT)test-bpf.bin: $(OUTPUT)test-libbpf.bin: $(BUILD) -lbpf +$(OUTPUT)test-libbpf-strings.bin: + $(BUILD) + $(OUTPUT)test-sdt.bin: $(BUILD) diff --git a/tools/build/feature/test-libbpf-strings.c b/tools/build/feature/test-libbpf-strings.c new file mode 100644 index 000000000000..83e6c45f5c85 --- /dev/null +++ b/tools/build/feature/test-libbpf-strings.c @@ -0,0 +1,10 @@ +// SPDX-License-Identifier: GPL-2.0 +#include + +int main(void) +{ + struct btf_dump_type_data_opts opts; + + opts.emit_strings = 0; + return opts.emit_strings; +} diff --git a/tools/perf/Documentation/perf-check.txt b/tools/perf/Documentation/perf-check.txt index a764a4629220..799982d8d868 100644 --- a/tools/perf/Documentation/perf-check.txt +++ b/tools/perf/Documentation/perf-check.txt @@ -52,6 +52,7 @@ feature:: dwarf-unwind / HAVE_DWARF_UNWIND_SUPPORT auxtrace / HAVE_AUXTRACE_SUPPORT libbfd / HAVE_LIBBFD_SUPPORT + libbpf-strings / HAVE_LIBBPF_STRINGS_SUPPORT libcapstone / HAVE_LIBCAPSTONE_SUPPORT libcrypto / HAVE_LIBCRYPTO_SUPPORT libdw-dwarf-unwind / HAVE_LIBDW_SUPPORT diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config index d1ea7bf44964..affe5e173920 100644 --- a/tools/perf/Makefile.config +++ b/tools/perf/Makefile.config @@ -595,8 +595,16 @@ ifndef NO_LIBELF LIBBPF_STATIC := 1 $(call detected,CONFIG_LIBBPF) CFLAGS += -DHAVE_LIBBPF_SUPPORT + LIBBPF_INCLUDE = $(LIBBPF_DIR)/.. endif endif + + FEATURE_CHECK_CFLAGS-libbpf-strings="-I$(LIBBPF_INCLUDE)" + $(call feature_check,libbpf-strings) + ifeq ($(feature-libbpf-strings), 1) + $(call detected,CONFIG_LIBBPF_STRINGS) + CFLAGS += -DHAVE_LIBBPF_STRINGS_SUPPORT + endif endif endif # NO_LIBBPF endif # NO_LIBELF diff --git a/tools/perf/builtin-check.c b/tools/perf/builtin-check.c index 9a509cb3bb9a..f4827f0ddb47 100644 --- a/tools/perf/builtin-check.c +++ b/tools/perf/builtin-check.c @@ -43,6 +43,7 @@ struct feature_status supported_features[] = { FEATURE_STATUS("dwarf-unwind", HAVE_DWARF_UNWIND_SUPPORT), FEATURE_STATUS("auxtrace", HAVE_AUXTRACE_SUPPORT), FEATURE_STATUS_TIP("libbfd", HAVE_LIBBFD_SUPPORT, "Deprecated, license incompatibility, use BUILD_NONDISTRO=1 and install binutils-dev[el]"), + FEATURE_STATUS("libbpf-strings", HAVE_LIBBPF_STRINGS_SUPPORT), FEATURE_STATUS("libcapstone", HAVE_LIBCAPSTONE_SUPPORT), FEATURE_STATUS("libcrypto", HAVE_LIBCRYPTO_SUPPORT), FEATURE_STATUS("libdw-dwarf-unwind", HAVE_LIBDW_SUPPORT), -- 2.25.1