[PATCH v2 2/2] fuzz: link fuzz programs with `make all` on Linux
- From
Josh Steadmon <steadmon@google.com>
- Date
- Apr 11, 2024, 18:14 UTC
- Message-ID
- <8846a7766a1e14373272f7115d37a3b774f51a71.1712858920.git.steadmon@google.com>
- In-Reply-To
- <cover.1712858920.git.steadmon@google.com>
Since 5e47215080 (fuzz: add basic fuzz testing target., 2018-10-12), we have compiled object files for the fuzz tests as part of the default 'make all' target. This helps prevent bit-rot in lesser-used parts of the codebase, by making sure that incompatible changes are caught at build time.
However, since we never linked the fuzzer executables, this did not protect us from link-time errors. As of 8b9a42bf48 (fuzz: fix fuzz test build rules, 2024-01-19), it's now possible to link the fuzzer executables without using a fuzzing engine and a variety of compiler-specific (and compiler-version-specific) flags, at least on Linux. So let's add a platform-specific option in config.mak.uname to link the executables as part of the default `make all` target.
Since linking the fuzzer executables without a fuzzing engine does not require a C++ compiler, we can change the FUZZ_PROGRAMS build rule to use $(CC) by default. This avoids compiler mis-match issues when overriding $(CC) but not $(CXX). When we *do* want to actually link with a fuzzing engine, we can set $(FUZZ_CXX). The build instructions in the CI fuzz-smoke-test job and in the Makefile comment have been updated accordingly.
While we're at it, we can consolidate some of the fuzzer build instructions into one location in the Makefile.
Suggested-by: Junio C Hamano <gitster@pobox.com> Helped-by: Jeff King <peff@peff.net> Signed-off-by: Josh Steadmon <steadmon@google.com> --- Makefile | 51 +++++++++++++++++------------ ci/run-build-and-minimal-fuzzers.sh | 2 +- config.mak.uname | 1 + 3 files changed, 32 insertions(+), 22 deletions(-)
diff --git a/Makefile b/Makefile index c43c1bd1a0..b9e97ad3b9 100644 --- a/Makefile +++ b/Makefile @@ -409,6 +409,9 @@ include shared.mak # to the "<name>" of the corresponding `compat/fsmonitor/fsm-settings-<name>.c` # that implements the `fsm_os_settings__*()` routines. # +# Define LINK_FUZZ_PROGRAMS if you want `make all` to also build the fuzz test +# programs in oss-fuzz/. +# # === Optional library: libintl === # # Define NO_GETTEXT if you don't want Git output to be translated. @@ -752,23 +755,6 @@ SCRIPTS = $(SCRIPT_SH_GEN) \ ETAGS_TARGET = TAGS -# If you add a new fuzzer, please also make sure to run it in -# ci/run-build-and-minimal-fuzzers.sh so that we make sure it still links and -# runs in the future. -FUZZ_OBJS += oss-fuzz/dummy-cmd-main.o -FUZZ_OBJS += oss-fuzz/fuzz-commit-graph.o -FUZZ_OBJS += oss-fuzz/fuzz-config.o -FUZZ_OBJS += oss-fuzz/fuzz-date.o -FUZZ_OBJS += oss-fuzz/fuzz-pack-headers.o -FUZZ_OBJS += oss-fuzz/fuzz-pack-idx.o -.PHONY: fuzz-objs -fuzz-objs: $(FUZZ_OBJS) - -# Always build fuzz objects even if not testing, to prevent bit-rot. -all:: $(FUZZ_OBJS) - -FUZZ_PROGRAMS += $(patsubst %.o,%,$(filter-out %dummy-cmd-main.o,$(FUZZ_OBJS))) - # Empty... EXTRA_PROGRAMS = @@ -2372,6 +2358,29 @@ ifndef NO_TCLTK endif $(QUIET_SUBDIR0)templates $(QUIET_SUBDIR1) SHELL_PATH='$(SHELL_PATH_SQ)' PERL_PATH='$(PERL_PATH_SQ)' +# If you add a new fuzzer, please also make sure to run it in +# ci/run-build-and-minimal-fuzzers.sh so that we make sure it still links and +# runs in the future. +FUZZ_OBJS += oss-fuzz/dummy-cmd-main.o +FUZZ_OBJS += oss-fuzz/fuzz-commit-graph.o +FUZZ_OBJS += oss-fuzz/fuzz-config.o +FUZZ_OBJS += oss-fuzz/fuzz-date.o +FUZZ_OBJS += oss-fuzz/fuzz-pack-headers.o +FUZZ_OBJS += oss-fuzz/fuzz-pack-idx.o +.PHONY: fuzz-objs +fuzz-objs: $(FUZZ_OBJS) + +# Always build fuzz objects even if not testing, to prevent bit-rot. +all:: $(FUZZ_OBJS) + +FUZZ_PROGRAMS += $(patsubst %.o,%,$(filter-out %dummy-cmd-main.o,$(FUZZ_OBJS))) + +# Build fuzz programs when possible, even without the necessary fuzzing support, +# to prevent bit-rot. +ifdef LINK_FUZZ_PROGRAMS +all:: $(FUZZ_PROGRAMS) +endif + please_set_SHELL_PATH_to_a_more_modern_shell: @$$(:) @@ -3857,22 +3866,22 @@ cover_db_html: cover_db # # An example command to build against libFuzzer from LLVM 11.0.0: # -# make CC=clang CXX=clang++ \ +# make CC=clang FUZZ_CXX=clang++ \ # CFLAGS="-fsanitize=fuzzer-no-link,address" \ # LIB_FUZZING_ENGINE="-fsanitize=fuzzer,address" \ # fuzz-all # +FUZZ_CXX ?= $(CC) FUZZ_CXXFLAGS ?= $(ALL_CFLAGS) .PHONY: fuzz-all +fuzz-all: $(FUZZ_PROGRAMS) $(FUZZ_PROGRAMS): %: %.o oss-fuzz/dummy-cmd-main.o $(GITLIBS) GIT-LDFLAGS - $(QUIET_LINK)$(CXX) $(FUZZ_CXXFLAGS) -o $@ $(ALL_LDFLAGS) \ + $(QUIET_LINK)$(FUZZ_CXX) $(FUZZ_CXXFLAGS) -o $@ $(ALL_LDFLAGS) \ -Wl,--allow-multiple-definition \ $(filter %.o,$^) $(filter %.a,$^) $(LIBS) $(LIB_FUZZING_ENGINE) -fuzz-all: $(FUZZ_PROGRAMS) - $(UNIT_TEST_PROGS): $(UNIT_TEST_BIN)/%$X: $(UNIT_TEST_DIR)/%.o $(UNIT_TEST_DIR)/test-lib.o $(GITLIBS) GIT-LDFLAGS $(call mkdir_p_parent_template) $(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) \ diff --git a/ci/run-build-and-minimal-fuzzers.sh b/ci/run-build-and-minimal-fuzzers.sh index a51076d18d..797d65c661 100755 --- a/ci/run-build-and-minimal-fuzzers.sh +++ b/ci/run-build-and-minimal-fuzzers.sh @@ -7,7 +7,7 @@ group "Build fuzzers" make \ CC=clang \ - CXX=clang++ \ + FUZZ_CXX=clang++ \ CFLAGS="-fsanitize=fuzzer-no-link,address" \ LIB_FUZZING_ENGINE="-fsanitize=fuzzer,address" \ fuzz-all diff --git a/config.mak.uname b/config.mak.uname index d0dcca2ec5..9107b4ae2b 100644 --- a/config.mak.uname +++ b/config.mak.uname @@ -68,6 +68,7 @@ ifeq ($(uname_S),Linux) ifneq ($(findstring .el7.,$(uname_R)),) BASIC_CFLAGS += -std=c99 endif + LINK_FUZZ_PROGRAMS = YesPlease endif ifeq ($(uname_S),GNU/kFreeBSD) HAVE_ALLOCA_H = YesPlease
-- 2.44.0.683.g7961c838ac-goog