[ovs-dev] [PATCH] oss-fuzz: Move oss-fuzz test harnesses and fuzzer configs to ovs source repo

Bhargava Shastry bshastry at sect.tu-berlin.de
Mon Jul 16 09:45:40 UTC 2018


Oops, here's the link failure log:

```
/usr/lib/gcc/x86_64-linux-gnu/5.4.0/../../../x86_64-linux-gnu/crt1.o: In
function `_start':
(.text+0x20): undefined reference to `main'
clang-7: error: linker command failed with exit code 1 (use -v to see
invocation)
Makefile:4159: recipe for target 'tests/oss-fuzz/flow_extract_target' failed
make: *** [tests/oss-fuzz/flow_extract_target] Error 1
fuzzers build failed.
```

The main symbol is provided by libfuzzer (clang++ -lFuzzingEngine)

Regards,
Bhargava

On 07/16/2018 11:36 AM, Bhargava Shastry wrote:
> Hi Ben,
> 
>> Never mind that one, I failed to check in some of that.
>>
>> I sent it formally:
>>         https://patchwork.ozlabs.org/patch/942118/
> 
> Thanks for the patch. This fixes the previous error. Now, there are some
> new errors during the compilation/linking process. I think most of this
> can be fixed if I figure out how automake works. In a nutshell, here's
> the problem:
> 
> - oss-fuzz provides compilation flags that can be plugged in like so
> ```
> CC=clang
> CXX=clang++
> CFLAGS=-O1 -fno-omit-frame-pointer -gline-tables-only
> -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION -fsanitize=address
> -fsanitize-address-use-after-scope -fsanitize=fuzzer-no-link
> CXXFLAGS=-O1 -fno-omit-frame-pointer -gline-tables-only
> -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION -fsanitize=address
> -fsanitize-address-use-after-scope -fsanitize=fuzzer-no-link -stdlib=libc++
> ```
> 
> And here's what I used to do before
> 
> - Use clang and CFLAGS above plus some additional includes to compile
> each of the fuzzer tests
> - Use clang++ and additional linker flags to link these into a fuzzer binary
> 
> Now, I see that the compilation works
> ```
> depbase=`echo tests/oss-fuzz/flow_extract_target.o | sed
> 's|[^/]*$|.deps/&|;s|\.o$||'`;\
> clang -DHAVE_CONFIG_H -I.    -I ./include -I ./include -I ./lib -I ./lib
> -I/usr/include   -Wstrict-prototypes -Wall -Wextra -Wno-sign-compare
> -Wpointer-arith -Wformat -Wformat-security -Wswitch-enum
> -Wunused-parameter -Wbad-function-cast -Wcast-align -Wstrict-prototypes
> -Wold-style-definition -Wmissing-prototypes -Wmissing-field-initializers
> -Wthread-safety -fno-strict-aliasing -Wswitch-bool
> -Wlogical-not-parentheses -Wsizeof-array-argument -Wshift-negative-value
> -Qunused-arguments -Wshadow -Wno-null-pointer-arithmetic    -O1
> -fno-omit-frame-pointer -gline-tables-only
> -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION -fsanitize=address
> -fsanitize-address-use-after-scope -fsanitize=fuzzer-no-link -MT
> tests/oss-fuzz/flow_extract_target.o -MD -MP -MF $depbase.Tpo -c -o
> tests/oss-fuzz/flow_extract_target.o
> tests/oss-fuzz/flow_extract_target.c &&\
> mv -f $depbase.Tpo $depbase.Po
> ```
> 
> However, the linking fails
> ```
> libtool: link: clang -Wstrict-prototypes -Wall -Wextra -Wno-sign-compare
> -Wpointer-arith -Wformat -Wformat-security -Wswitch-enum
> -Wunused-parameter -Wbad-function-cast -Wcast-align -Wstrict-prototypes
> -Wold-style-definition -Wmissing-prototypes -Wmissing-field-initializers
> -Wthread-safety -fno-strict-aliasing -Wswitch-bool
> -Wlogical-not-parentheses -Wsizeof-array-argument -Wshift-negative-value
> -Qunused-arguments -Wshadow -Wno-null-pointer-arithmetic -O1
> -fno-omit-frame-pointer -gline-tables-only
> -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION -fsanitize=address
> -fsanitize-address-use-after-scope -fsanitize=fuzzer-no-link -o
> tests/oss-fuzz/flow_extract_target tests/oss-fuzz/flow_extract_target.o
> -L/usr/lib lib/.libs/libopenvswitch.a -lssl -lcrypto -latomic
> ```
> 
> I think adding -lFuzzingEngine should fix this but another variable
> between my build script and automake is the use of clang++ for linking.
> 
> Do you know how I can experiment with different linker flags and
> compiler/linker in automake?
> 
> Regards,
> Bhargava
> 
> 

-- 
Bhargava Shastry <bshastry at sect.tu-berlin.de>
Security in Telecommunications
TU Berlin / Telekom Innovation Laboratories
Ernst-Reuter-Platz 7, Sekr TEL 17 / D - 10587 Berlin, Germany
phone: +49 30 8353 58235
Keybase: https://keybase.io/bshastry



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