WIP: use a trampoline for FLF functions to intercept timings

[bwoebi]

They don't check EG(vm_interrupt) by design, so we manually handle this.

[datadog-datadog-prod-us1]

⚠️ Tests

✨ Fix all issues with Cursor

⚠️ Warnings

❄️ 19 New flaky tests detected

profiling/tests/phpt/allocation_bind_static_01.phpt ([profiling] sampling shouldn't crash on `ZEND_BIND_STATIC` opcode) from php.profiling.tests.phpt (Datadog) (Fix with Cursor)

001- int(1)
002- string(1) "x"
003- int(1)
004- int(5)
001+

profiling/tests/phpt/allocation_func_get_args.phpt ([profiling] sampling shouldn't crash on `ZEND_FUNC_GET_ARGS` opcode) from php.profiling.tests.phpt (Datadog) (Fix with Cursor)

001- int(1)
002- string(1) "x"
003- int(1)
004- array(2) {
005-   [0]=>
006-   string(6) "string"
007-   [1]=>
008-   int(0)
009- }
010- Done.
...

profiling/tests/phpt/allocation_generator_01.phpt ([profiling] profiling should not crash during a `ZEND_GENERATOR_CREATE`) from php.profiling.tests.phpt (Datadog) (Fix with Cursor)

001- Fatal error: Allowed memory size of %d bytes exhausted %s
001+

View all

🧪 1032 Tests failed

    testSearchPhpBinaries from integration.DDTrace\Tests\Integration\PHPInstallerTest (Fix with Cursor)

    testSimplePushAndProcess from laravel-58-test.DDTrace\Tests\Integrations\Laravel\V5_8\QueueTest (Fix with Cursor)

testSimplePushAndProcess from laravel-8x-test.DDTrace\Tests\Integrations\Laravel\V8_x\QueueTest (Datadog) (Fix with Cursor)

DDTrace\Tests\Integrations\Laravel\V8_x\QueueTest::testSimplePushAndProcess
Test code or tested code printed unexpected output: spanLinksTraceId: 6981d34e0000000061ef575b249f934c
tid: 6981d34e00000000
hexProcessTraceId: 61ef575b249f934c
hexProcessSpanId: b0b6779f5e325f1f
processTraceId: 7056955190080934732
processSpanId: 12733496522800520991

View all

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: ab68993 | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.20%. Comparing base (9de150f) to head (ab68993).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3595      +/-   ##
==========================================
- Coverage   62.21%   62.20%   -0.02%     
==========================================
  Files         141      141              
  Lines       13387    13387              
  Branches     1753     1753              
==========================================
- Hits         8329     8327       -2     
- Misses       4260     4263       +3     
+ Partials      798      797       -1     

see 1 file with indirect coverage changes

---

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[morrisonlevi]

I assume this can run afoul of permissions somehow, since we're making executable code at runtime? I'm not well versed here, and yes, if the JIT is enabled you'd have to have that capability anyway, but I'm trying to understand implications of this WIP.

[pr-commenter]

Benchmarks [ profiler ]

Benchmark execution time: 2026-02-03 11:00:07

Comparing candidate commit ab68993 in PR branch bob/prof-flf-test with baseline commit 9de150f in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 28 metrics, 8 unstable metrics.

[bwoebi]

@morrisonlevi dynasmrt takes care of setting RX permissions after compiling the code. As long as you're not running this under a hardened runtime (like app store apps or android (?)), there's no fundamental problem. Also I currently call assembler.finalize().unwrap() (which takes care of settign RX) - proper usage should just handle the potential error here and abort.

[cataphract]

I assume original is not returning anything, because you're writing over RAX.

[bwoebi]

Correct

[cataphract]

this overwrites x30/lr, aren't you gonna lose the original return location of the handler? so when br x16 returns, it goes back to calling interrupt_addr

[bwoebi]

Ah, right. call on x86_64 pushes %eip to the stack, but blr doesn't.

[bwoebi]

Fixed up, is it correct now?