Example: snap_tool fails with "Check failed: std::filesystem::exists(p)" error when processing valid input

[23-cpu]

I encountered an issue while using the snap_tool in the Silifuzz project. When attempting to process valid raw x86 machine code, the tool fails with an error indicating that a required file or dependency is missing (Check failed: std::filesystem::exists(p)). Despite ensuring the environment is set up as per the documentation, the tool does not generate the expected output or snapshot.

Steps to Reproduce

$echo -en '\xFF\xC0' > /tmp/inc_eax

$SILIFUZZ_BIN_DIR/tools/snap_tool --raw print /tmp/inc_eax

I am expecting this below.

Metadata:
Id: inc_eax
Architecture: x86_64 Linux
Completeness: complete
Registers:
gregs (non-0 only)
rax = 0x20000000
....

The tool fails with the following error:

WARNING: All log messages before absl::InitializeLog() is called are written to STDERR
F0000 00:00:1733272965.389669 625799 data_dependency.cc:37] Check failed: std::filesystem::exists(p)
*** Check failure stack trace: ***
@ 0xad7684 absl::log_internal::LogMessage::SendToLog()
@ 0xad74b9 absl::log_internal::LogMessage::Flush()
@ 0xad7ab9 absl::log_internal::LogMessageFatal::~LogMessageFatal()
@ 0x9d857f silifuzz::GetDataDependencyFilepathBazelabi:cxx11
@ 0x9d802e silifuzz::GetDataDependencyFilepathabi:cxx11
@ 0x9d7ed8 silifuzz::RunnerLocationabi:cxx11
@ 0x84695e silifuzz::MakingConfig::Default()
@ 0x83e677 silifuzz::CreateSnapshotFromRawInstructions()
@ 0x84062e silifuzz::SnapToolMain()
@ 0x8436e1 main
@ 0xd9fbc4 __libc_start_call_main
Aborted

Could you please confirm if there are additional data dependencies that need to be explicitly set up or included for the snap_tool to work? Additionally, is there a way to debug what file/path std::filesystem::exists(p) is checking for?

Environment
Running on a google cloud instance
Debian GNU/Linux 12 (bookworm)
gcc 12.2.0

Thanks

[ksteuck]

I suspect it's not finding the runner binary. Runtime data dependencies in bazel are a little bit fragile unfortunately. Please try explicitly setting --runner=${SILIFUZZ_BIN_DIR}/runner/reading_runner_main_nolibc, this should fix the problem.

[23-cpu]

Unfortunately, it did not resolve the issue. I explicitly set the --runner argument as instructed, but I am still encountering the same error. Here is the command I used and the output I received:

$SILIFUZZ_BIN_DIR/tools/snap_tool --raw print /tmp/inc_eax --runner=${SILIFUZZ_BIN_DIR}/runner/reading_runner_main_nolibc

[ksteuck]

Try $SILIFUZZ_BIN_DIR/tools/snap_tool --runner=${SILIFUZZ_BIN_DIR}/runner/reading_runner_main_nolibc --raw print /tmp/inc_eax instead but first make sure that the path ${SILIFUZZ_BIN_DIR}/runner/reading_runner_main_nolibc is correct and the file exists

[23-cpu]

Unfortunately it still did not work. I tried creating a simple snapshot too, and it was giving the same output.

[ncbray]

I am able to reproduce the issue. It looks like the dependency finding code for the Bazel build assumes that you're invoking the tools through Bazel. This works, for example:

bazel run //tools:snap_tool -- --raw print /tmp/inc_eax

It will also work if you first cd bazel-bin.

Basically when you run the tool directly it is looking for $CWD/runner/reading_runner_main_nolibc rather than inside the bazel-bin dir. Further more, even when you override the binary it still does the search and the check fails.

Step 1, I will make sure it doesn't search for the binary when it doesn't need to.
Step 2, I will make the searching logic more robust somehow.

[ncbray]

Tip-of-tree snap_tool should now work when you pass an explicit --runner path.
I am still thinking through if there's an easy way to make the automatic searching work better.