fix: use PathBuf instead of String for guest binary and crash dump paths

[midsterx]

Currently, we do not allow non-UTF-8 paths for loading guest binaries and crash dumps. This PR replaces String-backed filesystem paths with PathBuf, thus allowing non-UTF-8 paths.

Resolves #1518

[Copilot]

Pull request overview

This PR standardizes filesystem path handling in Hyperlight’s host/guest loading and crash dump code by replacing String-backed paths with PathBuf, improving correctness for non-UTF8 paths and reducing lossy conversions at API boundaries.

Changes:

• Update GuestBinary::FilePath (and related callers) to use PathBuf rather than String.
• Update crashdump plumbing to carry PathBuf through the API (generate_crashdump_to_dir, HYPERLIGHT_CORE_DUMP_DIR, file path formatting).
• Update tests, examples, benches, and fuzz targets to pass PathBuf paths; add a Unix-only regression test for loading from a non-UTF8 filename.

Reviewed changes

Copilot reviewed 35 out of 35 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/hyperlight_testing/src/lib.rs	Add *_as_pathbuf helpers; keep *_as_string wrappers for compatibility.
src/hyperlight_host/tests/wit_test.rs	Switch test guest path acquisition to PathBuf.
src/hyperlight_host/tests/snapshot_goldens/fixtures.rs	Use PathBuf for fixture guest binary paths.
src/hyperlight_host/tests/sandbox_host_tests.rs	Update sandbox construction to pass PathBuf guest paths.
src/hyperlight_host/tests/common/mod.rs	Return PathBuf guest paths for shared test helpers.
src/hyperlight_host/src/sandbox/uninitialized.rs	Change GuestBinary::FilePath to PathBuf; update canonicalization and add non-UTF8 path test.
src/hyperlight_host/src/sandbox/uninitialized_evolve.rs	Update evolve tests to use PathBuf guest paths.
src/hyperlight_host/src/sandbox/snapshot/mod.rs	Pass PathBuf into ExeInfo::from_file during snapshot creation.
src/hyperlight_host/src/sandbox/snapshot/file_tests.rs	Update snapshot tests and crashdump directory calls to PathBuf/&Path.
src/hyperlight_host/src/sandbox/outb.rs	Update outb tests to use PathBuf guest paths.
src/hyperlight_host/src/sandbox/mod.rs	Update sandbox module tests to use PathBuf guest paths.
src/hyperlight_host/src/sandbox/initialized_multi_use.rs	Change generate_crashdump_to_dir to accept Into<PathBuf> and plumb into crashdump generator.
src/hyperlight_host/src/metrics/mod.rs	Update metrics tests to use PathBuf guest paths.
src/hyperlight_host/src/mem/mgr.rs	Update memory manager tests to use PathBuf guest paths.
src/hyperlight_host/src/mem/exe.rs	Change ExeInfo::from_file to take &Path; update tests accordingly.
src/hyperlight_host/src/hypervisor/mod.rs	Update hypervisor tests to use PathBuf guest paths.
src/hyperlight_host/src/hypervisor/hyperlight_vm/x86_64.rs	Remove string filename extraction; pass Option<PathBuf> into crashdump context.
src/hyperlight_host/src/hypervisor/gdb/mod.rs	Update GDB mem access tests to use PathBuf guest paths.
src/hyperlight_host/src/hypervisor/crashdump.rs	Store binary path as PathBuf; use var_os and PathBuf end-to-end for output paths.
src/hyperlight_host/examples/tracing/main.rs	Use PathBuf guest path helper in example.
src/hyperlight_host/examples/tracing-otlp/main.rs	Use PathBuf guest path helper in example.
src/hyperlight_host/examples/tracing-chrome/main.rs	Use PathBuf guest path helper in example.
src/hyperlight_host/examples/metrics/main.rs	Use PathBuf guest path helper in example.
src/hyperlight_host/examples/map-file-cow-test/main.rs	Pass PathBuf into GuestBinary::FilePath.
src/hyperlight_host/examples/logging/main.rs	Use PathBuf guest path helper in example.
src/hyperlight_host/examples/hello-world/main.rs	Pass PathBuf into GuestBinary::FilePath.
src/hyperlight_host/examples/guest-debugging/main.rs	Pass PathBuf into GuestBinary::FilePath for debug example/tests.
src/hyperlight_host/examples/func_ctx/main.rs	Use PathBuf guest path helper in example.
src/hyperlight_host/examples/crashdump/main.rs	Update crashdump example functions to take &Path / use PathBuf throughout.
src/hyperlight_host/benches/benchmarks.rs	Update benchmarks to pass PathBuf guest paths.
fuzz/fuzz_targets/host_print.rs	Switch fuzz harness guest path acquisition to PathBuf.
fuzz/fuzz_targets/host_call.rs	Switch fuzz harness guest path acquisition to PathBuf.
fuzz/fuzz_targets/guest_trace.rs	Switch fuzz harness guest path acquisition to PathBuf.
fuzz/fuzz_targets/guest_call.rs	Switch fuzz harness guest path acquisition to PathBuf.
CHANGELOG.md	Document breaking API change: guest/crashdump path APIs now use PathBuf.

[jsturtevant]

Why was this removed?

[midsterx]

It was removed because the filename duplicated information already contained in the binary PathBuf.

Previously, we stored both binary and filename. Now that we are using PathBuf, I removed filename from being passed.

The filename is derived later in crashdump.rs, where the ELF metadata actually requires text:

  let filename = ctx
      .binary
      .as_deref()
      .and_then(|path| path.file_name())
      .map_or("<unknown>".to_string(), |name| {
          name.to_string_lossy().into_owned()
      });

[jsturtevant]

Does this file exist?

[midsterx]

The file does not exist yet. I intended to create it for testing purposes, which would automatically get deleted (by TempDir's Drop) at the end of the test function’s scope.