ruby: support EC offset extraction for statically-linked Ruby#1227
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fabled merged 3 commits intoopen-telemetry:mainfrom Mar 19, 2026
Merged
ruby: support EC offset extraction for statically-linked Ruby#1227fabled merged 3 commits intoopen-telemetry:mainfrom
fabled merged 3 commits intoopen-telemetry:mainfrom
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This was referenced Mar 4, 2026
ruby: support EC offset extraction for statically-linked Ruby
Shopify/opentelemetry-ebpf-profiler#28
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ianks
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In principle the changes make sense to me. Would recommend a Gopher take a closer look though since my Go knowledge is limited
This was referenced Mar 17, 2026
For statically-linked Ruby binaries (bin/ruby rather than libruby.so), TLS descriptors are not available. Instead, rb_current_ec_noinline accesses the execution context directly via a TP-relative offset (FS:offset on x86_64, MRS tpidr_el0 + ADD on aarch64). This reuses the asm/amd.ExtractTLSOffset and asm/arm.ExtractTLSOffset infrastructure from the Python TLS PR (open-telemetry#1109) to disassemble rb_current_ec_noinline and extract the offset. Also changes current_ec_tpbase_tls_offset from u64 to s64 since static TLS offsets (local exec model) are negative on x86_64. Also adds RUBY_DISABLE_GC env var support to the loop.rb test script to allow capturing coredumps without GC interference.
Adds coredump tests for a statically-linked Ruby 3.4.7 binary on both arm64 and amd64, exercising the binRubyRegex match and extractEcTLSOffset() disassembly path for finding ruby_current_ec via direct TP-relative offset. Captured via gdb attach + breakpoint on rb_vm_exec to ensure a clean snapshot deep in the Ruby VM stack.
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florianl
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This was referenced Apr 14, 2026
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What
Support profiling statically-linked Ruby binaries (
bin/rubywith nolibruby.so) by extracting the execution context (EC) TLS offset directly from therb_current_ec_noinlinefunction's disassembly.Fixes #884
Related to #883 (handles static case, at least for ruby)
Why
The existing Ruby profiler only matches
libruby*.sovia regex and finds the EC via TLSDESC relocations. Statically-linked Ruby has no TLSDESC — insteadrb_current_ec_noinlineaccesses EC directly viaFS:offset(x86_64) orMRS tpidr_el0(aarch64). Without this change, statically-linked Ruby processes produce no Ruby frames at all.How
binRubyRegexto matchbin/rubyin addition tolibruby*.soextractEcTLSOffset()ininterpreter/ruby/ec.gothat disassemblesrb_current_ec_noinlineusing the existingasm/amd.ExtractTLSOffsetandasm/arm.ExtractTLSOffsetinfrastructure from python: get the Thread State from a Thread-local #1109 (Python TLS)VisitSymbolswhen the symbol is LOCAL (not in.dynsym) — fixes a nil pointer panic in the GNU hash lookup pathcurrent_ec_tpbase_tls_offsetfromu64tos64since static TLS offsets are negative on x86_64 (e.g.FS:0xfffffffffffffff8= -8)RUBY_DISABLE_GCenv var support to the coredump test scriptloop.rbNOTE: This depends on coredump artifacts which need to be added to the CI modulestore, they've been uploaded to a shared drive that @florianl has access to. Please re-run CI after uploading these artifacts.