fix: unwinding for binaries compiled without eh_frame_hdr

[not-matthias]

No description provided.

[codspeed-hq]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 7 untouched benchmarks

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_{Comparing cod-2769-runner-fails-to-extract-symbols-unwind-data-for-valgrind (41f4db9) with main (7e86f11)}

[greptile-apps]

Greptile Summary

This PR introduces UnwindDataV4, which makes eh_frame_hdr and eh_frame_hdr_svma optional fields, fixing stack unwinding for binaries compiled without ld --eh-frame-hdr (e.g. Valgrind's statically-linked tools). The existing V3 binary artifacts are transparently upgraded via a From<V3> impl that wraps the previously-required header data in Some.

• New data version (UnwindDataV4): eh_frame_hdr/eh_frame_hdr_svma are now Option; unwind_data_from_elf no longer bails when the .eh_frame_hdr section is absent, and serialized V3 files are automatically upgraded on read.
• All call sites updated: jit_dump.rs wraps the always-present JIT header in Some, all five insta snapshot files are regenerated, and a new binary test artifact (unwind_data_v4.bin) plus a Valgrind LFS binary are added for integration tests.
• Backward compatibility preserved: V1 and V2 remain rejected by UnwindData::parse, and UnwindDataV2::parse now also rejects V4, with roundtrip tests covering every combination.

Confidence Score: 5/5

Safe to merge. The change is additive: a required binary field becomes optional, V3 artifacts are automatically upgraded on read, and all existing call sites are updated.

The version migration path is correct and tested end-to-end. V3 artifacts are upgraded via From wrapping fields in Some, all snapshot tests are regenerated, and a new integration test against a real Valgrind binary validates the None path. No logic breakage is apparent.

No files require special attention.

Important Files Changed

Filename	Overview
crates/runner-shared/src/unwind_data.rs	Adds UnwindDataV4 with optional eh_frame_hdr/eh_frame_hdr_svma, bumps the UnwindData type alias to V4, updates parse/save_to, and adds comprehensive roundtrip tests.
src/executor/wall_time/profiler/perf/unwind_data.rs	unwind_data_from_elf now silently accepts a missing .eh_frame_hdr by removing the .context() bail-out; adds a valgrind test that asserts None for the missing header.
src/executor/wall_time/profiler/perf/jit_dump.rs	JIT path wraps eh_frame_hdr and eh_frame_hdr_svma in Some(...) to match the new optional struct fields.
crates/runner-shared/testdata/unwind_data_v4.bin	New binary test artifact for V4 deserialization round-trip tests (generated by the #[ignore] generator test).
testdata/perf_map/valgrind	Git-LFS pointer to a Valgrind statically-linked binary used by the new integration test for binaries without .eh_frame_hdr.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Read .unwind_data bytes] --> B[bincode::deserialize as UnwindDataCompat]
    B --> C{variant?}
    C -- V1 --> D[bail: cannot parse V1 as V4]
    C -- V2 --> E[bail: cannot parse V2 as V4]
    C -- V3 --> F[From<V3> for V4: wraps hdr fields in Some]
    C -- V4 --> G[return as-is]
    F --> G
    G --> H{eh_frame_hdr?}
    H -- Some --> I[use hdr as lookup index into .eh_frame]
    H -- None --> J[rebuild index directly from .eh_frame - e.g. Valgrind statically-linked tools]

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_{Reviews (2): Last reviewed commit: "docs(runner-shared): add unwind data ver..." | Re-trigger Greptile}

[GuillaumeLagrange]

olgtm