On Tue, Jun 25, 2024 at 7:52 AM Jan Beulich <jbeul...@suse.com> wrote: > > On 25.06.2024 13:12, Tamas K Lengyel wrote: > > On Tue, Jun 25, 2024 at 2:00 AM Jan Beulich <jbeul...@suse.com> wrote: > >> > >> On 24.06.2024 23:23, Tamas K Lengyel wrote: > >>> On Mon, Jun 24, 2024 at 11:55 AM Jan Beulich <jbeul...@suse.com> wrote: > >>>> > >>>> On 21.06.2024 21:14, Tamas K Lengyel wrote: > >>>>> @@ -58,6 +58,9 @@ afl-harness: afl-harness.o $(OBJS) cpuid.o wrappers.o > >>>>> afl-harness-cov: afl-harness-cov.o $(patsubst %.o,%-cov.o,$(OBJS)) > >>>>> cpuid.o wrappers.o > >>>>> $(CC) $(CFLAGS) $(GCOV_FLAGS) $(addprefix > >>>>> -Wl$(comma)--wrap=,$(WRAPPED)) $^ -o $@ > >>>>> > >>>>> +libfuzzer-harness: $(OBJS) cpuid.o > >>>>> + $(CC) $(CFLAGS) $(LIB_FUZZING_ENGINE) -fsanitize=fuzzer $^ -o $@ > >>>> > >>>> What is LIB_FUZZING_ENGINE? I don't think we have any use of that in the > >>>> tree anywhere. > >>> > >>> It's used by oss-fuzz, otherwise it's not doing anything. > >>> > >>>> > >>>> I'm further surprised you get away here without wrappers.o. > >>> > >>> Wrappers.o was actually breaking the build for oss-fuzz at the linking > >>> stage. It works just fine without it. > >> > >> I'm worried here, to be honest. The wrappers serve a pretty important > >> role, and I'm having a hard time seeing why they shouldn't be needed > >> here when they're needed both for the test and afl harnesses. Could > >> you add some more detail on the build issues you encountered? > > > > With wrappers.o included doing the build in the oss-fuzz docker > > (ubuntu 20.04 base) fails with: > > > > ... > > clang -O1 -fno-omit-frame-pointer -gline-tables-only > > -Wno-error=enum-constexpr-conversion > > -Wno-error=incompatible-function-pointer-types > > -Wno-error=int-conversion -Wno-error=deprecated-declarations > > -Wno-error=implicit-function-declaration -Wno-error=implicit-int > > -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION -fsanitize=address > > -fsanitize-address-use-after-scope -fsanitize=fuzzer-no-link -m64 > > -DBUILD_ID -fno-strict-aliasing -std=gnu99 -Wall -Wstrict-prototypes > > -Wno-unused-but-set-variable -Wno-unused-local-typedefs -g3 -Werror > > -Og -fno-omit-frame-pointer > > -D__XEN_INTERFACE_VERSION__=__XEN_LATEST_INTERFACE_VERSION__ -MMD -MP > > -MF .libfuzzer-harness.d -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE > > -I/src/xen/tools/fuzz/x86_instruction_emulator/../../../tools/include > > -D__XEN_TOOLS__ -iquote . -fsanitize=fuzzer -fsanitize=fuzzer > > -Wl,--wrap=fwrite -Wl,--wrap=memcmp -Wl,--wrap=memcpy > > -Wl,--wrap=memset -Wl,--wrap=printf -Wl,--wrap=putchar -Wl,--wrap=puts > > -Wl,--wrap=snprintf -Wl,--wrap=strstr -Wl,--wrap=vprintf > > -Wl,--wrap=vsnprintf fuzz-emul.o x86-emulate.o x86_emulate/0f01.o > > x86_emulate/0fae.o x86_emulate/0fc7.o x86_emulate/decode.o > > x86_emulate/fpu.o cpuid.o wrappers.o -o libfuzzer-harness > > /usr/bin/ld: /usr/bin/ld: DWARF error: invalid or unhandled FORM value: 0x25 > > /usr/local/lib/clang/18/lib/x86_64-unknown-linux-gnu/libclang_rt.fuzzer.a(fuzzer.o): > > in function `std::__Fuzzer::__libcpp_snprintf_l(char*, unsigned long, > > __locale_struct*, char const*, ...)': > > cxa_noexception.cpp:(.text._ZNSt8__Fuzzer19__libcpp_snprintf_lEPcmP15__locale_structPKcz[_ZNSt8__Fuzzer19__libcpp_snprintf_lEPcmP15__locale_structPKcz]+0x9a): > > undefined reference to `__wrap_vsnprintf' > > clang: error: linker command failed with exit code 1 (use -v to see > > invocation) > > make: *** [Makefile:62: libfuzzer-harness] Error 1 > > rm x86-emulate.c wrappers.c cpuid.c > > make: Leaving directory '/src/xen/tools/fuzz/x86_instruction_emulator' > > ERROR:__main__:Building fuzzers failed. > > Hmm, yes, means we'll need an actual vsnprintf() wrapper, not just a > declaration thereof.
I don't really get what this wrapper accomplishes and as I said, fuzzing works with oss-fuzz just fine without it. Tamas
