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feat(crashtracking): GOT patch sigaction - #2448

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feat(crashtracking): GOT patch sigaction#2448
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@gyuheon0h

@gyuheon0h gyuheon0h commented Sep 2, 2026 •
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What does this PR do?

Intercepts sigaction calls with hook_symbol GOT patching so the crashtracker can detect when application code overwrites a monitored signal handler after initialization.

The hook covers all callers including the statically-linked test binary; internal sigaction calls from chain_signal_handler (which runs inside the signal handler) are safe because SIG_DFL/SIG_IGN handlers are filtered out before any async work is attempted (this is done before the hook_symbol anyways), and the hook always forwards using the stored original function pointer rather than through a GOT entry so there.

Motivation

Some runtimes may overwrite our handlers. It would be good to know when this is happening.

Additional Notes

This is a stacked PR. This change is minimal -- just adding the patch, and printing out. Sending actual telemetry is done feat(crashtracking): send telemetry if instrumented application sigactions our signal

How to test the change?

Describe here in detail how the change can be validated.

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gyuheon0h commented Sep 2, 2026 •
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This stack of pull requests is managed by Graphite. Learn more about stacking.

@gyuheon0h gyuheon0h changed the title GOT patch sigaction feat(crashtracking): GOT patch sigaction Sep 2, 2026
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📚 Documentation Check Results

⚠️ 1112 documentation warning(s) found

📦 libdd-crashtracker - 1112 warning(s)

Updated: 2026-09-03 17:55:51 UTC | Commit: 11609bc | missing-docs job results

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🔒 Cargo Deny Results

⚠️ 3 issue(s) found, showing only errors (advisories, bans, sources)

📦 libdd-crashtracker - 3 error(s)

Show output 
error[vulnerability]: Invalid pointer dereference in `fmt::Pointer` impl for `Atomic` and `Shared` when the underlying pointer is invalid
   ┌─ /home/runner/work/libdatadog/libdatadog/Cargo.lock:60:1
   │
60 │ crossbeam-epoch 0.9.18 registry+https://github.com/rust-lang/crates.io-index
   │ ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ security vulnerability detected
   │
   ├ ID: RUSTSEC-2026-0204
   ├ Advisory: https://rustsec.org/advisories/RUSTSEC-2026-0204
   ├ Affected versions of `fmt::Display` dereference the underlying pointer. This causes a invalid pointer dereference e.g., when a pointer created with `Atomic::null` or `Shared::null`. `fmt::Debug` impls and pre-0.9 `fmt::Display` impls, which do not dereference pointers, are not affected by this issue.
   ├ Announcement: https://github.com/crossbeam-rs/crossbeam/pull/1276
   ├ Solution: Upgrade to >=0.9.20 (try `cargo update -p crossbeam-epoch`)
   ├ crossbeam-epoch v0.9.18
     └── crossbeam-deque v0.8.5
         └── rayon-core v1.12.1
             └── rayon v1.10.0
                 └── criterion v0.5.1
                     ├── (dev) libdd-crashtracker v2.0.1
                     └── (dev) libdd-ddsketch v1.1.1
                         └── libdd-telemetry v7.0.0
                             └── libdd-crashtracker v2.0.1 (*)

error[vulnerability]: h2 unbounded empty DATA frames
   ┌─ /home/runner/work/libdatadog/libdatadog/Cargo.lock:98:1
   │
98 │ h2 0.4.6 registry+https://github.com/rust-lang/crates.io-index
   │ ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ security vulnerability detected
   │
   ├ ID: RUSTSEC-2026-0258
   ├ Advisory: https://rustsec.org/advisories/RUSTSEC-2026-0258
   ├ The h2 crate, used internally by hyper, had a flaw that would accept and queue empty DATA frames without limit.
     If streams were not actively drained, this could lead to unbounded memory usage, or a panic if the length overflows.
     
     Low severity.
     
     Patched in v0.4.16.
   ├ Announcement: https://github.com/hyperium/hyper/security/advisories/GHSA-q83h-524g-xf6h
   ├ Solution: Upgrade to >=0.4.16 (try `cargo update -p h2`)
   ├ h2 v0.4.6
     └── hyper v1.6.0
         ├── httpmock v0.8.0-alpha.1
         │   └── (dev) libdd-telemetry v7.0.0
         │       └── libdd-crashtracker v2.0.1
         ├── hyper-rustls v0.27.7
         │   └── libdd-common v5.2.0
         │       ├── libdd-capabilities-impl v4.0.0
         │       │   ├── libdd-crashtracker v2.0.1 (*)
         │       │   ├── libdd-shared-runtime v3.0.0
         │       │   │   └── libdd-telemetry v7.0.0 (*)
         │       │   └── (dev) libdd-telemetry v7.0.0 (*)
         │       ├── (build) libdd-crashtracker v2.0.1 (*)
         │       ├── libdd-shared-runtime v3.0.0 (*)
         │       └── libdd-telemetry v7.0.0 (*)
         ├── hyper-util v0.1.17
         │   ├── httpmock v0.8.0-alpha.1 (*)
         │   ├── hyper-rustls v0.27.7 (*)
         │   └── libdd-common v5.2.0 (*)
         └── libdd-common v5.2.0 (*)

error[unsound]: Rand is unsound with a custom logger using `rand::rng()`
    ┌─ /home/runner/work/libdatadog/libdatadog/Cargo.lock:209:1
    │
209 │ rand 0.8.5 registry+https://github.com/rust-lang/crates.io-index
    │ ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ unsound advisory detected
    │
    ├ ID: RUSTSEC-2026-0097
    ├ Advisory: https://rustsec.org/advisories/RUSTSEC-2026-0097
    ├ It has been reported (by [@lopopolo](https://github.com/lopopolo)) that the `rand` library is [unsound](https://rust-lang.github.io/unsafe-code-guidelines/glossary.html#soundness-of-code--of-a-library) (i.e. that safe code using the public API can cause Undefined Behaviour) when all the following conditions are met:
      
      - The `log` and `thread_rng` features are enabled
      - A [custom logger](https://docs.rs/log/latest/log/#implementing-a-logger) is defined
      - The custom logger accesses `rand::rng()` (previously `rand::thread_rng()`) and calls any `TryRng` (previously `RngCore`) methods on `ThreadRng`
      - The `ThreadRng` (attempts to) reseed while called from the custom logger (this happens every 64 kB of generated data)
      - Trace-level logging is enabled or warn-level logging is enabled and the random source (the `getrandom` crate) is unable to provide a new seed
      
      `TryRng` (previously `RngCore`) methods for `ThreadRng` use `unsafe` code to cast `*mut BlockRng<ReseedingCore>` to `&mut BlockRng<ReseedingCore>`. When all the above conditions are met this results in an aliased mutable reference, violating the Stacked Borrows rules. Miri is able to detect this violation in sample code. Since construction of [aliased mutable references is Undefined Behaviour](https://doc.rust-lang.org/stable/nomicon/references.html), the behaviour of optimized builds is hard to predict.
    ├ Announcement: https://github.com/rust-random/rand/pull/1763
    ├ Solution: Upgrade to >=0.10.1 OR <0.10.0, >=0.9.3 OR <0.9.0, >=0.8.6 (try `cargo update -p rand`)
    ├ rand v0.8.5
      ├── libdd-common v5.2.0
      │   ├── libdd-capabilities-impl v4.0.0
      │   │   ├── libdd-crashtracker v2.0.1
      │   │   ├── libdd-shared-runtime v3.0.0
      │   │   │   └── libdd-telemetry v7.0.0
      │   │   │       └── libdd-crashtracker v2.0.1 (*)
      │   │   └── (dev) libdd-telemetry v7.0.0 (*)
      │   ├── (build) libdd-crashtracker v2.0.1 (*)
      │   ├── libdd-shared-runtime v3.0.0 (*)
      │   └── libdd-telemetry v7.0.0 (*)
      ├── libdd-crashtracker v2.0.1 (*)
      ├── (dev) libdd-ddsketch v1.1.1
      │   └── libdd-telemetry v7.0.0 (*)
      └── proptest v1.5.0
          └── (dev) libdd-common v5.2.0 (*)

advisories FAILED, bans ok, sources ok

Updated: 2026-09-03 17:57:20 UTC | Commit: 11609bc | dependency-check job results

gyuheon0h
gyuheon0h commented Sep 2, 2026
View reviewed changes
Comment thread libdd-crashtracker/src/collector/sigaction_interceptor.rs
oldact: *mut libc::sigaction,
) -> libc::c_int {
// Check if this signal is one we monitor.
if (0..64).contains(&signum)

@gyuheon0h gyuheon0h Sep 2, 2026 •
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I don't like this but clippy wont let me make the inverse check. Havent checked but probably compiles down to the same thing

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datadog-prod-us1-3 Bot commented Sep 2, 2026 •
edited by datadog-prod-us1-6 Bot
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Tests

✅ All CI checks and tests passed.

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 76.40%
• Overall Coverage: 77.13% (+0.01%)

This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 6f13ff4 | Docs | View more details | Give us feedback!

@pr-commenter

pr-commenter Bot commented Sep 2, 2026 •
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Benchmarks

Comparison

Benchmark execution time: 2026-09-03 18:07:46

Comparing candidate commit 6f13ff4 in PR branch gyuheon0h/PROF-15892-sigaction-got with baseline commit 13c5242 in branch main.

📊 Benchmarking dashboard

Found 0 performance improvements and 0 performance regressions! Performance is the same for 1 metrics, 0 unstable metrics.

Explanation

This is an A/B test comparing a candidate commit's performance against that of a baseline commit. Performance changes are noted in the tables below as:

  • 🟩 = significantly better candidate vs. baseline
  • 🟥 = significantly worse candidate vs. baseline

We compute a confidence interval (CI) over the relative difference of means between metrics from the candidate and baseline commits, considering the baseline as the reference.

If the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD), the change is considered significant.

Feel free to reach out to #apm-benchmarking-platform on Slack if you have any questions.

More details about the CI and significant changes

You can imagine this CI as a range of values that is likely to contain the true difference of means between the candidate and baseline commits.

CIs of the difference of means are often centered around 0%, because often changes are not that big:

---------------------------------(------|---^--------)-------------------------------->
                              -0.6%    0%  0.3%     +1.2%
                                 |          |        |
         lower bound of the CI --'          |        |
sample mean (center of the CI) -------------'        |
         upper bound of the CI ----------------------'

As described above, a change is considered significant if the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD).

For instance, for an execution time metric, this confidence interval indicates a significantly worse performance:

----------------------------------------|---------|---(---------^---------)---------->
                                       0%        1%  1.3%      2.2%      3.1%
                                                  |   |         |         |
       significant impact threshold --------------'   |         |         |
                      lower bound of CI --------------'         |         |
       sample mean (center of the CI) --------------------------'         |
                      upper bound of CI ----------------------------------'

Candidate

Candidate benchmark details

Group 1

cpu_model git_commit_sha git_commit_date git_branch
Intel(R) Xeon(R) Platinum 8175M CPU @ 2.50GHz 6f13ff4 1788457207 gyuheon0h/PROF-15892-sigaction-got
scenario metric min mean ± sd median ± mad p75 p95 p99 max peak_to_median_ratio skewness kurtosis cv sem runs sample_size
receiver_entry_point/report/2644 execution_time 6.343ms 6.385ms ± 0.022ms 6.383ms ± 0.014ms 6.396ms 6.422ms 6.448ms 6.470ms 1.36% 0.910 1.563 0.34% 0.002ms 1 200
scenario metric 95% CI mean Shapiro-Wilk pvalue Ljung-Box pvalue (lag=1) Dip test pvalue
receiver_entry_point/report/2644 execution_time [6.382ms; 6.388ms] or [-0.047%; +0.047%] None None None

Baseline

Baseline benchmark details

Group 1

cpu_model git_commit_sha git_commit_date git_branch
Intel(R) Xeon(R) Platinum 8175M CPU @ 2.50GHz 13c5242 1788458243 main
scenario metric min mean ± sd median ± mad p75 p95 p99 max peak_to_median_ratio skewness kurtosis cv sem runs sample_size
receiver_entry_point/report/2644 execution_time 6.339ms 6.388ms ± 0.020ms 6.384ms ± 0.015ms 6.402ms 6.422ms 6.439ms 6.445ms 0.95% 0.289 -0.308 0.32% 0.001ms 1 200
scenario metric 95% CI mean Shapiro-Wilk pvalue Ljung-Box pvalue (lag=1) Dip test pvalue
receiver_entry_point/report/2644 execution_time [6.385ms; 6.390ms] or [-0.044%; +0.044%] None None None

@dd-octo-sts

dd-octo-sts Bot commented Sep 2, 2026 •
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Artifact Size Benchmark Report

aarch64-alpine-linux-musl
Artifact Baseline Commit Change
/aarch64-alpine-linux-musl/lib/libdatadog_profiling.so 8.45 MB 8.45 MB 0% (0 B) 👌
/aarch64-alpine-linux-musl/lib/libdatadog_profiling.a 91.32 MB 91.32 MB +0% (+1.62 KB) 👌
aarch64-unknown-linux-gnu
Artifact Baseline Commit Change
/aarch64-unknown-linux-gnu/lib/libdatadog_profiling.so 11.38 MB 11.38 MB +0% (+752 B) 👌
/aarch64-unknown-linux-gnu/lib/libdatadog_profiling.a 102.61 MB 102.61 MB -0% (-440 B) 👌
libdatadog-x64-windows
Artifact Baseline Commit Change
/libdatadog-x64-windows/debug/dynamic/datadog_profiling_ffi.dll 27.32 MB 27.32 MB 0% (0 B) 👌
/libdatadog-x64-windows/debug/dynamic/datadog_profiling_ffi.lib 96.08 KB 96.08 KB 0% (0 B) 👌
/libdatadog-x64-windows/debug/dynamic/datadog_profiling_ffi.pdb 185.42 MB 185.41 MB -0% (-8.00 KB) 👌
/libdatadog-x64-windows/debug/static/datadog_profiling_ffi.lib 804.05 MB 804.05 MB 0% (0 B) 👌
/libdatadog-x64-windows/release/dynamic/datadog_profiling_ffi.dll 9.00 MB 9.00 MB 0% (0 B) 👌
/libdatadog-x64-windows/release/dynamic/datadog_profiling_ffi.lib 96.08 KB 96.08 KB 0% (0 B) 👌
/libdatadog-x64-windows/release/dynamic/datadog_profiling_ffi.pdb 26.20 MB 26.20 MB 0% (0 B) 👌
/libdatadog-x64-windows/release/static/datadog_profiling_ffi.lib 52.21 MB 52.21 MB 0% (0 B) 👌
libdatadog-x86-windows
Artifact Baseline Commit Change
/libdatadog-x86-windows/debug/dynamic/datadog_profiling_ffi.dll 23.82 MB 23.82 MB 0% (0 B) 👌
/libdatadog-x86-windows/debug/dynamic/datadog_profiling_ffi.lib 97.58 KB 97.58 KB 0% (0 B) 👌
/libdatadog-x86-windows/debug/dynamic/datadog_profiling_ffi.pdb 190.44 MB 190.43 MB -0% (-8.00 KB) 👌
/libdatadog-x86-windows/debug/static/datadog_profiling_ffi.lib 787.48 MB 787.48 MB 0% (0 B) 👌
/libdatadog-x86-windows/release/dynamic/datadog_profiling_ffi.dll 6.96 MB 6.96 MB 0% (0 B) 👌
/libdatadog-x86-windows/release/dynamic/datadog_profiling_ffi.lib 97.58 KB 97.58 KB 0% (0 B) 👌
/libdatadog-x86-windows/release/dynamic/datadog_profiling_ffi.pdb 28.18 MB 28.18 MB 0% (0 B) 👌
/libdatadog-x86-windows/release/static/datadog_profiling_ffi.lib 49.70 MB 49.70 MB 0% (0 B) 👌
x86_64-alpine-linux-musl
Artifact Baseline Commit Change
/x86_64-alpine-linux-musl/lib/libdatadog_profiling.a 81.48 MB 81.48 MB -0% (-40 B) 👌
/x86_64-alpine-linux-musl/lib/libdatadog_profiling.so 9.41 MB 9.41 MB 0% (0 B) 👌
x86_64-unknown-linux-gnu
Artifact Baseline Commit Change
/x86_64-unknown-linux-gnu/lib/libdatadog_profiling.a 97.21 MB 97.21 MB -0% (-2.01 KB) 👌
/x86_64-unknown-linux-gnu/lib/libdatadog_profiling.so 11.46 MB 11.46 MB +0% (+536 B) 👌

@gyuheon0h
gyuheon0h force-pushed the gyuheon0h/PROF-15892-sigaction-got branch 2 times, most recently from 8440a0f to 070422d Compare September 3, 2026 15:36
@gyuheon0h gyuheon0h mentioned this pull request Sep 3, 2026
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@gyuheon0h
gyuheon0h force-pushed the gyuheon0h/PROF-15892-sigaction-got branch from 070422d to 6f13ff4 Compare September 3, 2026 17:53
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