llmdbg-dev
ce96a98829
- Native step/cont moved to __step_native/__cont_native; public step()/cont()
defined in prelude.js wrap them and dispatch JS listeners on each stop.
- addEventListener/removeEventListener/clearListeners/listeners() registry on
globalThis, persistent for the daemon lifetime (independent of ctx.reset()).
- Event object carries {state, prev, stop_reason} plus breakpoint_id/signal/
exit_code as appropriate. Implements the SPEC 'Event Listeners' + 'Core Loop'.
- No-listener fast path keeps existing scripts zero-cost.
- examples/smarm_ctx_switch.js: worked session inspecting smarm's naked-asm
context switch; README updated (status table, listener API, deferred list).
69 lines
2.5 KiB
JavaScript
69 lines
2.5 KiB
JavaScript
// examples/smarm_ctx_switch.js
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//
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// Demonstrates the v0.7 event-listener system by inspecting smarm's naked-asm
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// context switch. smarm (https://git.kalsbeek.dev/Markk116/smarm) is a green-
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// thread actor runtime whose core is two `#[naked]` switch shims that swap rsp
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// between a scheduler stack and an actor's mmap'd stack.
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//
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// Build the probe binary (frame pointers on, single scheduler thread):
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// cd smarm
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// RUSTFLAGS="-C force-frame-pointers=yes" cargo build --example ctx_switch_probe
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//
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// Then pipe this script into llmdbg, substituting:
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// - SPAWN_PATH: absolute path to the built ctx_switch_probe-<hash> binary
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// - ACTOR_ASM: mangled name of switch_to_actor_asm (from `nm BIN | grep`)
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// - SCHED: mangled name of switch_to_scheduler
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//
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// What it shows:
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// 1. A 'breakpoint' listener that logs each switch with rsp + 16-alignment.
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// 2. A 'step' listener that single-steps the shim's tail (mov rsp,rax; the
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// six pops; ret) and proves the actor entry lands with rsp % 16 == 8 —
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// the x86-64 ABI state expected at a function entry reached via `call`.
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//
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// This was the session that caught the off-by-one-slot error in
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// init_actor_stack's layout comment (entry is at aligned_top-16, not -8).
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spawn("SPAWN_PATH")
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// --- (1) per-switch alignment trace via a breakpoint listener --------------
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ctx.sched = addr("SCHED")
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ctx.actor_asm = addr("ACTOR_ASM")
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addEventListener('breakpoint', e => {
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const sp = e.state.sp;
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const where = (e.state.pc === ctx.sched) ? "to_sched" : "to_actor";
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ctx.hits = (ctx.hits ?? 0) + 1;
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print(`#${ctx.hits} ${where} rsp=${hex(sp)} rsp%16=${sp % 16n}`);
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});
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bp.set(ctx.sched, "to_sched")
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bp.set(ctx.actor_asm, "to_actor")
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---END---
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// Drive through the first several switches. Each cont() fires the listener.
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for (let i = 0; i < 6; i++) {
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let r = cont();
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if (!r.startsWith("breakpoint")) { print("stop: " + r); break; }
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}
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---END---
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// --- (2) prove the ret lands at rsp%16==8 in the actor entry ---------------
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// Remove the breakpoint listener; add a step listener for the tail trace.
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clearListeners('breakpoint')
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// Reach `mov rsp,rax` (offset 0x17 in the shim) on the next switch_to_actor.
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ctx.movrsp = ctx.actor_asm + 0x17n
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bp.remove("to_sched")
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bp.remove("to_actor")
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bp.set(ctx.movrsp, "movrsp")
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cont()
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---END---
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clearListeners()
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addEventListener('step', e => {
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const ins = e.state.disasm(1)[0];
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print(`${hex(e.state.pc)} rsp=${hex(e.state.sp)} %16=${e.state.sp % 16n} ${ins.text}`);
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});
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// mov rsp,rax ; pop r15..rbx (6) ; ret ; first insn of entry
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step(8)
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---END---
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