Adds the -fast-16-labels flag, which enables efficient instrumentation
for DFSan when the user needs <=16 labels. The instrumentation
eliminates most branches and most calls to __dfsan_union or
__dfsan_union_load.
Reviewed By: vitalybuka
Differential Revision: https://reviews.llvm.org/D84371
It broke the Windows build:
C:\b\s\w\ir\cache\builder\src\third_party\llvm\compiler-rt\lib\fuzzer\FuzzerDataFlowTrace.cpp(243): error C3861: 'setenv': identifier not found
This also reverts the follow-up r363327.
llvm-svn: 363358
Summary:
1. Do not create DFSan labels for the bytes which we do not trace. This is where we run out of labels at the first place.
2. When dumping the traces on the disk, make sure to offset the label identifiers by the number of the first byte in the trace range.
3. For the last label, make sure to write it at the last position of the trace bit string, as that label represents the input size, not any particular byte.
Also fixed the bug with division in python which I've introduced when migrated the scripts to Python3 (`//` is required for integral division).
Otherwise, the scripts are wasting too much time unsuccessfully trying to
collect and process traces from the long inputs. For more context, see
https://github.com/google/oss-fuzz/issues/1632#issuecomment-481761789
Reviewers: kcc
Reviewed By: kcc
Subscribers: delcypher, #sanitizers, llvm-commits
Tags: #llvm, #sanitizers
Differential Revision: https://reviews.llvm.org/D60538
llvm-svn: 358311
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
Summary:
Experimental data flow tracer for fuzz targets.
Allows to tell which bytes of the input affect which functions of the fuzz target.
We previously attempted to use DFSan directly in the libFuzzer process,
and that didn't work nicely.
Now we will try to collect the data flow information for the seed corpus
in a separate process (using this tracer), and then use it in the regular libFuzzer runs.
Reviewers: morehouse, pcc, Dor1s
Reviewed By: morehouse, Dor1s
Subscribers: delcypher, #sanitizers, llvm-commits
Differential Revision: https://reviews.llvm.org/D46666
llvm-svn: 332029
Matt Morehouse