[2.BF] Synthetic silph::WorkerCtx spawn (round 18 — opt-in landing)

Adds infrastructure to synthesise the silph::WorkerCtx that AUDIT-058/059
identified as never reached by ours' static-init chain (real chain entry
sits in audit-059 round 9's wrong-vtable wedge at sub_82172BA0+0x1E8).
Ctx layout follows round 5's live hexdump from canary:

  +0x00   vtable = 0x8200A1E8
  +0x04   self
  +0x08   intrusive list head -> self
  +0x0C   init flag = 1
  +0x10   packed byte field
  +0x18   2x float ~1.0 (UI rates)
  +0x24   flag = 1
  +0x28..+0x30  3x foreign-arena pointers (left NULL — see below)
  +0x54..+0x84  4x X_KEVENT auto-reset, state=0
  +0x94..+0xC4  4x X_KEVENT manual-reset, state=1 (pre-signaled)
  +0x210..+0x250  4-entry intrusive work-ring, empty

Worker spawn mirrors AUDIT-048's audio-worker pattern in
xaudio_register_render_driver: per-worker allocate_thread_image +
state.scheduler.spawn with r3 = ctx_ptr. Trigger fires at the first
dat/* VFS open (ours' earliest is dat/files.tbl), which is when canary
runs the equivalent chain.

ROUND 18 OUTCOME — opt-in only:

With workers spawned Ready (XENIA_SILPH_SYNTH=1), boot CRASHES at
cycle ~5.5M with PC=0 on hw=1, just after worker_3 (entry 0x825065B8)
spawns. Per task constraints this is STOP-and-report: the ctx fields
+0x28/+0x2C/+0x30 (foreign heap pointers — canary's 0x30057018,
0xBCE25640, 0xBE568F00, distinct arenas per audit-059 round 7) are
left NULL, and the worker bodies plausibly dereference one of them.
Synthesising those is a fresh investigation (round 19+).

With workers spawned Suspended (XENIA_SILPH_SYNTH=suspend), boot
completes normally (11 spawns, VdSwap=1, KeSetEvent=2,
KeReleaseSemaphore=1 — matches default baseline). The ctx remains
materialised in guest memory at the logged VA for downstream probing.

Default (env var unset): no synth, no regression.

Files:
  crates/xenia-kernel/src/silph_synth.rs   (new, 225 LOC)
  crates/xenia-kernel/src/lib.rs           (+1 LOC, register module)
  crates/xenia-kernel/src/exports.rs       (+37 LOC, hook in open_vfs_file)
  crates/xenia-kernel/src/state.rs         (+18 LOC, 4 silph_synth_* fields)

Tests: cargo test --release --workspace = 765 pass / 0 fail.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/xenia-kernel/src/exports.rs

@@ -980,6 +980,43 @@ fn open_vfs_file(
     // see a null handle later and trigger `XamShowDirtyDiscErrorUI`.
     let path = crate::path::object_attributes_to_vfs_path(mem, obj_attrs_ptr)
         .unwrap_or_default();
+    // AUDIT-2.BF — synthetic silph::WorkerCtx spawn. AUDIT-058/059
+    // identified that ours never activates the 6-level static caller
+    // ladder that ends in `sub_825070F0`, so the four worker threads
+    // it would normally spawn (entries 0x82506528/58/88/B8) never run.
+    // Canary's chain originally fires right after `DiscImageDevice::
+    // ResolvePath("\\dat\\movie")` (audit-058); ours never opens
+    // `dat/movie` because tid=13 wedges before reaching it. We
+    // therefore trigger on the first `dat/*` open — the earliest
+    // such open in ours is `dat/files.tbl` (immediately preceding
+    // tid=12/13 spawn at audit-059 round 1).
+    //
+    // **Round 18 finding** (this commit): when the workers are
+    // spawned runnable, they fault almost immediately (`PC=0` at
+    // cycle ~5.5M on the hw thread carrying worker_3), preempting
+    // ours' boot before the normal guest threads even spawn. The
+    // ctx layout from audit-059 round 5 is incomplete — at least
+    // one of `[+0x28]`/`[+0x2C]`/`[+0x30]` (the three foreign-
+    // arena pointers) must be populated for the worker bodies to
+    // run. Synthesising those is a fresh investigation (round 19+).
+    //
+    // Until then the synth path is **opt-in**: set
+    // `XENIA_SILPH_SYNTH=1` to enable the runnable spawn (will
+    // crash boot), or `XENIA_SILPH_SYNTH=suspend` to spawn but keep
+    // them in `Blocked(Suspended)` (lets boot complete with the
+    // ctx materialised in memory for downstream probes). Default:
+    // disabled — preserves the existing boot trajectory.
+    if !state.silph_synth_done && path.starts_with("dat/") {
+        match std::env::var("XENIA_SILPH_SYNTH").as_deref() {
+            Ok("1") | Ok("run") | Ok("runnable") => {
+                let _ = crate::silph_synth::spawn_silph_workers(state, mem, false);
+            }
+            Ok("suspend") | Ok("suspended") => {
+                let _ = crate::silph_synth::spawn_silph_workers(state, mem, true);
+            }
+            _ => {}
+        }
+    }
     if path.is_empty() && obj_attrs_ptr == 0 {
         if handle_out != 0 {
             mem.write_u32(handle_out, 0);

crates/xenia-kernel/src/lib.rs

@@ -3,6 +3,7 @@ pub mod exports;
 pub mod interrupts;
 pub mod objects;
 pub mod path;
+pub mod silph_synth;
 pub mod state;
 pub mod thread;
 pub mod ui_bridge;

crates/xenia-kernel/src/silph_synth.rs

@@ -0,0 +1,225 @@
+//! AUDIT-2.BF — synthetic spawn of the silph::WorkerCtx worker quartet.
+//!
+//! AUDIT-058/059 traced a 6-level static-caller ladder
+//! (`sub_824F7800 ← sub_824F7CD0 ← sub_824F8398 ← sub_821B55D8 ← sub_821B6DF4`,
+//! topped by virtual-dispatch from `sub_82172BA0+0x1E8`) that activates
+//! `sub_825070F0` in canary at ~1× / 30 s, kicking off four worker threads
+//! initialised against a single ~0x440-byte ctx. In ours none of those PCs
+//! fire (audit-059 round 9 confirmed sub_821B6DF4 = 0×, real chain entry =
+//! virtual-dispatch from sub_82172BA0+0x1E8 hits wrong-vtable slot).
+//!
+//! Rather than chase the wrong-vtable break, this module reproduces the end
+//! state directly: at the first observation of a load-bearing VFS path
+//! (`dat/movie`), we synthesise the ctx structure in guest memory per audit-
+//! 059 round 5's live hexdump and spawn the four worker entry points the
+//! same way AUDIT-048's audio host-pump spawns its dedicated client worker.
+//!
+//! The ctx is opaque to the workers — only fields they dereference matter.
+//! Per round 5 dump (`audit-runs/audit-059-handle-disambiguation/round5-ctx-
+//! dump/canary.log`):
+//!
+//!   +0x00  vtable        = 0x8200A1E8  (XEX .rdata, valid in both engines)
+//!   +0x04  self          = ctx
+//!   +0x08  intrusive head= ctx
+//!   +0x0C  init flag     = 1
+//!   +0x10  packed byte   = 0x01000000
+//!   +0x18  float ~1.0    = 0x3F7FCCCC
+//!   +0x1C  float ~1.0    = 0x3F802D83
+//!   +0x24  flag          = 1
+//!   +0x28..+0x30        = three foreign pointers, NULL initially
+//!   +0x54..+0x84        = 4× X_KEVENT auto-reset, state=0
+//!   +0x94..+0xC4        = 4× X_KEVENT manual-reset, state=1
+//!   +0x210..+0x250      = 4-entry intrusive work-ring, empty
+//!
+//! Worker entries (each takes r3 = ctx_ptr):
+//!   0x82506528, 0x82506558, 0x82506588, 0x825065B8
+
+use xenia_cpu::scheduler::{BlockReason, SpawnParams};
+use xenia_cpu::ThreadRef;
+use xenia_memory::{GuestMemory, MemoryAccess};
+
+use crate::objects::KernelObject;
+use crate::state::{GuestMemoryPcr, KernelState};
+use crate::thread::allocate_thread_image;
+
+/// XEX `.rdata` vtable for the silph::WorkerCtx singleton (audit-059 round 5).
+const SILPH_CTX_VTABLE: u32 = 0x8200_A1E8;
+
+/// 4-element fixed entry table — guest text PCs for the four worker bodies.
+const SILPH_WORKER_ENTRIES: [u32; 4] = [
+    0x8250_6528,
+    0x8250_6558,
+    0x8250_6588,
+    0x8250_65B8,
+];
+
+/// Round 0x440 up to a page so the ctx alloc never straddles a page boundary
+/// in heap_alloc's bookkeeping.
+const SILPH_CTX_SIZE: u32 = 0x500;
+
+/// 64 KiB worker stack (mirrors AUDIT-048 audio worker), half of canary's
+/// 128 KiB default.
+const SILPH_WORKER_STACK: u32 = 0x10_000;
+
+/// Idempotently synthesise the silph::WorkerCtx and spawn the four worker
+/// threads it normally drives.
+///
+/// `suspended` controls whether the spawned threads enter the runqueue as
+/// `Ready` (false) or as `Blocked(Suspended)` (true). Use `true` for
+/// diagnostic baselines where you want the ctx materialised in guest memory
+/// for downstream probes but don't want the worker bodies executing (e.g.
+/// when round-5 ctx fields like the foreign-arena pointers at +0x28/+0x2C/
+/// +0x30 are still NULL and the workers would fault on first dereference).
+///
+/// Returns the ctx VA on the first call; on subsequent calls returns the
+/// cached VA without re-spawning. Failures inside spawn are logged but the
+/// `synth_done` latch is still flipped so we don't retry-loop.
+///
+/// Mirrors the AUDIT-048 audio-worker spawn pattern in
+/// `xaudio_register_render_driver` (`exports.rs:3122`).
+pub fn spawn_silph_workers(
+    state: &mut KernelState,
+    mem: &GuestMemory,
+    suspended: bool,
+) -> Option<u32> {
+    if state.silph_synth_done {
+        return Some(state.silph_synth_ctx);
+    }
+    state.silph_synth_done = true;
+
+    let Some(ctx) = state.heap_alloc(SILPH_CTX_SIZE, mem) else {
+        tracing::warn!("silph_synth: heap_alloc({:#x}) failed for ctx", SILPH_CTX_SIZE);
+        return None;
+    };
+    state.silph_synth_ctx = ctx;
+
+    // Zero the entire ctx page first — heap_alloc returns freshly mapped
+    // memory but we want the audit-059-round-5 layout to be canonical
+    // regardless of any future allocator behaviour change.
+    for off in (0..SILPH_CTX_SIZE).step_by(4) {
+        mem.write_u32(ctx + off, 0);
+    }
+
+    // ---- Header scalars (per audit-059 round 5 hexdump) ----
+    mem.write_u32(ctx + 0x00, SILPH_CTX_VTABLE);
+    mem.write_u32(ctx + 0x04, ctx); // self
+    mem.write_u32(ctx + 0x08, ctx); // intrusive list head pointing at self
+    mem.write_u32(ctx + 0x0C, 0x0000_0001); // init flag / refcount
+    mem.write_u32(ctx + 0x10, 0x0100_0000); // packed byte field
+    mem.write_u32(ctx + 0x18, 0x3F7F_CCCC); // float ~1.0 (UI rate A)
+    mem.write_u32(ctx + 0x1C, 0x3F80_2D83); // float ~1.0 (UI rate B)
+    mem.write_u32(ctx + 0x24, 0x0000_0001);
+    // +0x28..+0x30 = three foreign pointers (heap arenas BE/701C/BCA4/B1B6
+    // per audit-059 round 7). Left NULL — if any worker dereferences these
+    // we'll see a guest fault and treat that as the next gate.
+
+    // ---- 4× X_KEVENT auto-reset at +0x54/+0x64/+0x74/+0x84, state = 0 ----
+    // X_DISPATCH_HEADER layout (canary xobject.h:35):
+    //   +0x00  type (u8: 0=manual-event, 1=auto-event, 2=mutant, ...)
+    //   +0x01  abandoned (u8)
+    //   +0x02  size (u8 dwords)
+    //   +0x03  inserted (u8)
+    //   +0x04  signal_state (u32 BE)
+    //   +0x08..+0x0F  list_head (two pointers — self-link = empty list)
+    for i in 0..4u32 {
+        let off = ctx + 0x54 + (i * 0x10);
+        mem.write_u8(off, 1); // type = auto-reset Event
+        mem.write_u32(off + 4, 0); // signal_state = 0
+        // List head self-link denotes empty waiter list.
+        mem.write_u32(off + 8, off + 8);
+        mem.write_u32(off + 12, off + 8);
+    }
+    // ---- 4× X_KEVENT manual-reset at +0x94..+0xC4, state = 1 (pre-signaled) ----
+    for i in 0..4u32 {
+        let off = ctx + 0x94 + (i * 0x10);
+        mem.write_u8(off, 0); // type = manual-reset Event
+        mem.write_u32(off + 4, 1); // signal_state = 1 (pre-signaled)
+        mem.write_u32(off + 8, off + 8);
+        mem.write_u32(off + 12, off + 8);
+    }
+
+    // ---- 4-entry intrusive work-ring at +0x210, initially empty ----
+    // Each entry: [+0]=0x01000000 [+4]=0 [+8]=self_ptr [+0xC]=self_ptr.
+    for i in 0..4u32 {
+        let off = ctx + 0x210 + (i * 0x10);
+        mem.write_u32(off, 0x0100_0000);
+        mem.write_u32(off + 4, 0);
+        mem.write_u32(off + 8, off + 8);
+        mem.write_u32(off + 12, off + 8);
+    }
+
+    // +0x250 "XEN"-tagged descriptors and +0x2E0 resource-index table left
+    // zero — they may be populated lazily by the workers themselves.
+
+    // ---- Spawn the 4 worker guest threads ----
+    use std::sync::atomic::Ordering;
+    let mut spawned = 0usize;
+    for (i, &entry) in SILPH_WORKER_ENTRIES.iter().enumerate() {
+        let Some(image) = allocate_thread_image(state, mem, SILPH_WORKER_STACK, 0) else {
+            tracing::warn!("silph_synth: allocate_thread_image failed for worker {}", i);
+            continue;
+        };
+        let tid = state.next_thread_id.fetch_add(1, Ordering::Relaxed);
+        let handle = state.alloc_handle_for(KernelObject::Thread {
+            id: tid,
+            hw_id: None,
+            exit_code: None,
+            waiters: Vec::new(),
+        });
+        let tls_slot_count = state.next_tls_index.load(Ordering::Relaxed);
+        let params = SpawnParams {
+            entry,
+            start_context: ctx, // r3 = ctx_ptr
+            stack_base: image.stack_base,
+            stack_size: image.stack_size,
+            pcr_base: image.pcr_base,
+            tls_base: image.tls_base,
+            thread_handle: handle,
+            guest_tid: tid,
+            create_suspended: suspended,
+            is_initial: false,
+            tls_slot_count,
+            affinity_mask: 0,
+            priority: 0,
+            ideal_processor: None,
+        };
+        match state.scheduler.spawn(params, &mut GuestMemoryPcr(mem)) {
+            Ok(hw_id) => {
+                if let Some(KernelObject::Thread { hw_id: slot, .. }) =
+                    state.objects.get_mut(&handle)
+                {
+                    *slot = Some(hw_id);
+                }
+                let tref = ThreadRef::new(
+                    hw_id,
+                    (state.scheduler.slots[hw_id as usize].runqueue.len() - 1) as u16,
+                );
+                state.silph_synth_handles[i] = Some(handle);
+                state.silph_synth_refs[i] = Some(tref);
+                spawned += 1;
+                tracing::info!(
+                    "silph_synth: spawned worker {} tid={} handle={:#x} entry={:#010x} ctx={:#010x}",
+                    i, tid, handle, entry, ctx
+                );
+            }
+            Err(_) => {
+                tracing::warn!(
+                    "silph_synth: scheduler.spawn failed for worker {} entry={:#010x}",
+                    i, entry
+                );
+            }
+        }
+        // Avoid an unused-variable warning if BlockReason isn't referenced.
+        let _ = BlockReason::WaitAny {
+            handles: Vec::new(),
+            deadline: None,
+        };
+    }
+
+    tracing::info!(
+        "silph_synth: ctx={:#010x} workers_spawned={}/4",
+        ctx, spawned
+    );
+
+    Some(ctx)
+}

crates/xenia-kernel/src/state.rs

@@ -299,6 +299,20 @@ pub struct KernelState {
     pub dump_addrs: Vec<u32>,
     /// `--dump-section=BASE:LEN:PATH` end-of-run snapshot, page-gated by `is_mapped`.
     pub dump_section: Option<(u32, u32, std::path::PathBuf)>,
+    /// AUDIT-2.BF — synthetic silph::WorkerCtx spawn one-shot latch. Set on
+    /// first call to [`crate::silph_synth::spawn_silph_workers`] (triggered
+    /// by the first observation of a load-bearing VFS path such as
+    /// `dat/movie`), then reused — subsequent triggers are no-ops.
+    pub silph_synth_done: bool,
+    /// AUDIT-2.BF — VA of the synthesised silph::WorkerCtx. Zero before the
+    /// first spawn; set to the ctx base by `spawn_silph_workers`. Held on
+    /// the kernel state so future export hooks can find it (no caller does
+    /// yet — placeholder for round 19+ wiring).
+    pub silph_synth_ctx: u32,
+    /// AUDIT-2.BF — kernel handles for the 4 synthetic worker threads.
+    pub silph_synth_handles: [Option<u32>; 4],
+    /// AUDIT-2.BF — `ThreadRef` cache for the 4 synthetic workers.
+    pub silph_synth_refs: [Option<xenia_cpu::ThreadRef>; 4],
 }
 
 impl KernelState {
@@ -369,6 +383,10 @@ impl KernelState {
             lr_trace_writer: None,
             dump_addrs: Vec::new(),
             dump_section: None,
+            silph_synth_done: false,
+            silph_synth_ctx: 0,
+            silph_synth_handles: [None; 4],
+            silph_synth_refs: [None; 4],
         };
         crate::exports::register_exports(&mut state);
         crate::xam::register_exports(&mut state);