binutils: Fix fuzz_strings achieving 0% coverage

[rolbk]

Summary

Fix binutils fuzz_strings fuzzer which was achieving 0% coverage due to missing initialization.

Main Change

Fix missing global variable initialization in fuzz_strings.c

The harness was not initializing important global variables, most importantly string_min (minimum string length to print) which defaults to 0. This causes strings to get stuck in an endless loop printing zero-length strings, likely explaining the 0% coverage.

Further Changes

• Patch abort() in bfd/xsym.c - When --enable-targets=all is set, bfd_sym_read_header_v34() calls abort() for unimplemented v3.4/v3.5 xSYM format support, killing the fuzzer on malformed xSYM files. Replaced with return -1 to fall back to internal error handling.
• Add seed corpus for strings fuzzer - Added binary-samples corpus similar to other binutils fuzzers.

Testing

python3 infra/helper.py build_image binutils --pull
python3 infra/helper.py build_fuzzers binutils --clean
python3 infra/helper.py run_fuzzer --corpus-dir ./corpus binutils fuzz_strings -- -fork=6 -ignore_crashes=1 -max_total_time=86400
python3 infra/helper.py build_fuzzers --sanitizer coverage binutils
python3 infra/helper.py coverage binutils --no-serve --corpus-dir ./corpus --fuzz-target fuzz_strings

24h test run coverage results:

Path	Line Coverage	Function Coverage	Region Coverage
fuzz_strings.h	13.12% (111/846)	37.50% (6/16)	15.73% (123/782)

Related

@DavidKorczynski - Sorry for the ping: The old seed corpus for strings was removed in #6717. What was the reasoning behind that? Was this AFL-specific, or is this still relevant now? Thanks!

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[github-actions]

rolbk is a new contributor to projects/binutils. The PR must be approved by known contributors before it can be merged. The past contributors are: hunsche, amodra, hghwng, DonggeLiu