// examples/smarm_ctx_switch.js
//
// Demonstrates the v0.7 event-listener system by inspecting smarm's naked-asm
// context switch. smarm (https://git.kalsbeek.dev/Markk116/smarm) is a green-
// thread actor runtime whose core is two `#[naked]` switch shims that swap rsp
// between a scheduler stack and an actor's mmap'd stack.
//
// Build the probe binary (frame pointers on, single scheduler thread):
//   cd smarm
//   RUSTFLAGS="-C force-frame-pointers=yes" cargo build --example ctx_switch_probe
//
// Then pipe this script into llmdbg, substituting:
//   - SPAWN_PATH: absolute path to the built ctx_switch_probe-<hash> binary
//   - ACTOR_ASM:  mangled name of switch_to_actor_asm (from `nm BIN | grep`)
//   - SCHED:      mangled name of switch_to_scheduler
//
// What it shows:
//   1. A 'breakpoint' listener that logs each switch with rsp + 16-alignment.
//   2. A 'step' listener that single-steps the shim's tail (mov rsp,rax; the
//      six pops; ret) and proves the actor entry lands with rsp % 16 == 8 —
//      the x86-64 ABI state expected at a function entry reached via `call`.
//
// This was the session that caught the off-by-one-slot error in
// init_actor_stack's layout comment (entry is at aligned_top-16, not -8).

spawn("SPAWN_PATH")

// --- (1) per-switch alignment trace via a breakpoint listener --------------
ctx.sched = addr("SCHED")
ctx.actor_asm = addr("ACTOR_ASM")

addEventListener('breakpoint', e => {
  const sp = e.state.sp;
  const where = (e.state.pc === ctx.sched) ? "to_sched" : "to_actor";
  ctx.hits = (ctx.hits ?? 0) + 1;
  print(`#${ctx.hits} ${where} rsp=${hex(sp)} rsp%16=${sp % 16n}`);
});
bp.set(ctx.sched, "to_sched")
bp.set(ctx.actor_asm, "to_actor")
---END---

// Drive through the first several switches. Each cont() fires the listener.
for (let i = 0; i < 6; i++) {
  let r = cont();
  if (!r.startsWith("breakpoint")) { print("stop: " + r); break; }
}
---END---

// --- (2) prove the ret lands at rsp%16==8 in the actor entry ---------------
// Remove the breakpoint listener; add a step listener for the tail trace.
clearListeners('breakpoint')

// Reach `mov rsp,rax` (offset 0x17 in the shim) on the next switch_to_actor.
ctx.movrsp = ctx.actor_asm + 0x17n
bp.remove("to_sched")
bp.remove("to_actor")
bp.set(ctx.movrsp, "movrsp")
cont()
---END---

clearListeners()
addEventListener('step', e => {
  const ins = e.state.disasm(1)[0];
  print(`${hex(e.state.pc)} rsp=${hex(e.state.sp)} %16=${e.state.sp % 16n}  ${ins.text}`);
});
// mov rsp,rax ; pop r15..rbx (6) ; ret ; first insn of entry
step(8)
---END---