openharmony/arkcompiler_runtime_core
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arkcompiler_runtime_core/docs/runtime-debug-api.md
huangyu c658ccf319 Update runtime_core code 
Issue: https://gitee.com/openharmony/arkcompiler_runtime_core/issues/I5G96F
Test: Test262 suit, ark unittest, rk3568 XTS, ark previewer demo

Signed-off-by: huangyu <huangyu76@huawei.com>
Change-Id: I3f63d129a07deaa27a390f556dcaa5651c098185
2022-07-17 10:20:32 +08:00

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Runtime debug API

Requirements

  1. Runtime should support debugging on the platforms from low-end IoT devices to hi-end mobile phones.

Key Design Decisions

  1. Runtime doesn't patch apps' bytecode on the fly. Instead of it notification about changing bytecode pc is used.

  2. Runtime and debugger work in the same process. Debugger functionality is provided via shared library, that runtime loads when works in debugger mode. Debugger works in the own thread and responsibilies for thread management relies on it, runtime doesn't create/destroy threads.

Rationale

  1. As some low-end targets can store bytecode in ROM, runtime cannot patch app's bytecode on the fly. So it uses slower approach with interpreter instrumentation.

  2. To simplify communication beetween debugger and runtime (especially on microcontrollers) they are work in the same process. Debugger is loaded as shared library when it's necessary.

Specification / Implementation

To start runtime in the debug mode a debugger LoadableAgent is loaded, which usually represents a debugger shared library. It is created by the VM (see PandaVM::LoadDebuggerAgent()) as it is language-specific.

The loaded agent starts a debug session when necessary (see Runtime::StartDebugSession()). When starting the session, the JIT is disabled, and the tooling::Debugger object that implements tooling::DebugInterface - the point of interaction with the runtime - is created. The agent may access this using the Runtime::DebugSession::GetDebugger() method.

Runtime provides RuntimeNotificationManager class that allows to subscript for different events:

  • LoadModule - occurs when panda file is loaded by the runtime
  • BytecodePcChanged - occurs when bytecode pc is changed during interpretation (only if runtime works in debug mode)

tooling::Debugger subscribes to these events and notificates debugger via hooks.