Deprecate JIT code

[shankarseal]

JIT / interpret is not supported in runtime for any scenarios.
Hence, remove all support for JIT mode, including uBPF, and any dependency on fuzzing tests.

[Alan-Jowett]

Investigation & Implementation Plan

Problem Statement

JIT/interpret are not supported in runtime for any production scenarios. Only native execution mode (pre-compiled .sys drivers) is used. This allows removing the ubpf dependency and related fuzzing test infrastructure.

Goal: Remove all JIT and interpreter support, keeping only EBPF_EXECUTION_NATIVE mode.

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Key Findings

• Both JIT and interpreter use ubpf - the interpreter uses ubpf_create(), ubpf_load(), ubpf_exec(); JIT uses the compilation functions
• Removing JIT alone won't eliminate the ubpf dependency - both must be removed
• NativeOnlyDebug/NativeOnlyRelease configurations already disable both modes and can serve as reference

Architecture Impact

Component	Current State	After Deprecation
Execution modes	NATIVE, JIT, INTERPRET	NATIVE only
ubpf dependency	Required for JIT/interpret	Removed
ebpfsvc	JIT compilation service	Simplified (verification only)
Fuzzing tests	JIT-dependent	Remove or convert to native

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Scope of Changes

Category	Files Affected
Build system	Directory.Build.props, all .vcxproj files
Core execution	ebpf_program.c, ebpf_core_jit.c/h (delete)
API layer	ebpf_api.cpp, api_service.cpp, bpf_syscall.cpp
Type definitions	ebpf_execution_type.h, ebpf_protocol.h
uBPF removal	libs/ubpf/ (delete), external/ubpf submodule
Tests	6+ JIT-specific test files to delete, 10+ files to update

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Implementation Phases

Phase 1: Build System & Configuration

• Remove DisableJIT/DisableInterpreter build properties from Directory.Build.props
• Make JIT/interpreter always disabled
• Remove NativeOnlyDebug/NativeOnlyRelease distinction (all builds become native-only)

Phase 2: Type Definitions & Enums

• Remove EBPF_EXECUTION_JIT and EBPF_EXECUTION_INTERPRET from include/ebpf_execution_type.h
• Remove EBPF_CODE_JIT and EBPF_CODE_EBPF from libs/execution_context/ebpf_protocol.h
• Update EBPF_EXECUTION_ANY to map directly to native

Phase 3: Core Execution Context

• Delete: libs/execution_context/ebpf_core_jit.c and ebpf_core_jit.h
• Remove JIT/interpreter code paths from libs/execution_context/ebpf_program.c
• Remove ubpf VM creation/execution logic
• Remove JIT protocol functions (resolve_helper, resolve_map, get_ec_function)

Phase 4: API Layer

• Update libs/api/ebpf_api.cpp - remove #include "ubpf.h", JIT/interpret validation
• Update libs/service/api_service.cpp - remove JIT/interpret code type conversion

Phase 5: uBPF Dependency Removal

• Delete: libs/ubpf/ directory entirely (user and kernel wrappers)
• Remove: external/ubpf git submodule
• Clean up all .vcxproj files to remove ubpf references

Phase 6: RPC & Syscall Interface

• Update rpc_interface/rpc_client.h - remove JIT-related RPC functions
• Update libs/api/bpf_syscall.cpp - remove JIT resolve/get_ec_function calls

Phase 7: Tests Cleanup

• Delete JIT test files:
  • tests/api_test/api_test_jit.cpp and .h
  • tests/unit/libbpf_test_jit.cpp and .h
  • tests/end_to_end/end_to_end_jit.cpp and .h
  • libs/execution_context/unit/execution_context_unit_test_jit.cpp
• Update test macros: Remove DECLARE_JIT_TEST, DECLARE_INTERPRET_TEST
• Fuzzer cleanup: Evaluate fuzzers using interpreter mode

Phase 8: Documentation

• Update docs/GettingStarted.md, docs/DevelopmentGuide.md, README.md
• Remove JIT/interpreter execution mode references

Phase 9: Final Validation

• Update .gitmodules to remove ubpf reference
• Validate all build configurations
• Run all remaining tests for regressions

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Files to Delete

• libs/execution_context/ebpf_core_jit.c
• libs/execution_context/ebpf_core_jit.h
• libs/ubpf/ (entire directory)
• external/ubpf/ (submodule)
• tests/api_test/api_test_jit.*
• tests/unit/libbpf_test_jit.*
• tests/end_to_end/end_to_end_jit.*
• libs/execution_context/unit/execution_context_unit_test_jit.cpp

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Risks & Considerations

1. Breaking changes: Code using EBPF_EXECUTION_JIT or EBPF_EXECUTION_INTERPRET will fail to compile (intentional)
2. Fuzzing tests: Need to determine which fuzzers can continue without interpreter mode
3. Test coverage: Ensure native execution has equivalent coverage to removed JIT/interpret tests
4. External consumers: Downstream projects relying on JIT/interpret mode will need updates