feat(kernel): KRNBUG-XEX-001 — real XexCheckExecutablePrivilege from XEX header bitmap

Replace stub_return_zero with a canary-faithful implementation that
returns bit `priv` of the loaded XEX's XEX_HEADER_SYSTEM_FLAGS
(key 0x00030000) bitmap. Mirrors xenia-canary
xboxkrnl_modules.cc:22-39: `(flags >> priv) & 1` for priv < 32, else 0.

Plumbing:
- xenia-xex: header_keys::SYSTEM_FLAGS const + get_system_flags() accessor.
- xenia-kernel/state.rs: pub xex_system_flags: u32 + xex_priv_logged
  HashSet for one-shot per-priv tracing.
- xenia-app: kernel.xex_system_flags wired in cmd_exec_inner.
- xenia-kernel/exports.rs: real export body + unit test covering
  bits 10/11/0/64 + zero-flags case.

Sylpheed's bitmap is 0x00000400 (only XEX_SYSTEM_PAL50_INCOMPATIBLE,
bit 10). At -n 500M with the fix:
- XGetAVPack: 0 -> 1 (priv-10 gate at lr=0x824ab598 flipped).
- 10 other canary-only exports + 9 producer PCs + 3 parked handles
  unchanged. Priv-11 site at sub_824A9710 is downstream and still
  not reached — AV/crypto block aborts after XGetAVPack returns
  our placeholder 0x16 (canary returns 8/HDMI; Sylpheed accepts
  only 3/4/6/8 per xenia-canary xam_info.cc:250-251).

Tests 588 -> 589. Lockstep deterministic (3 reruns identical):
n50m goes 50000008 -> 50000005 instr / 407415 -> 407417 imp / swaps=2 /
draws=0. Goldens re-baselined (sylpheed_n50m, sylpheed_n2m); oracle
test green.

Full chain-of-effects + next-frontier hand-off in audit-findings.md
under KRNBUG-XEX-001.

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

audit-findings.md

@@ -4813,3 +4813,81 @@ If after the fix the producer is reached and dispatcher fields
 populate, the parked-waiter deadlock should resolve — or surface
 the next layer of bugs (e.g. signaling code reads non-zero handle
 but `wake_eligible_waiters` fails).
+
+### KRNBUG-XEX-001 — `XexCheckExecutablePrivilege` real impl (P0 fix landed)
+
+**Branch:** `xex-check-privilege/p0-real-impl` (no-ff merged to master).
+**Status:** LANDED 2026-05-04. Closes the priv-stub side of KRNBUG-AUDIT-005.
+
+**Implementation.** Replaced `stub_return_zero` at
+`crates/xenia-kernel/src/exports.rs:193` with a real implementation
+that reads the XEX `XEX_HEADER_SYSTEM_FLAGS` (key `0x00030000`)
+bitmap. Mirrors canary's `XexCheckExecutablePrivilege_entry`
+[xboxkrnl_modules.cc:22-39](../xenia-canary/src/xenia/kernel/xboxkrnl/xboxkrnl_modules.cc#L22-L39):
+`(flags >> priv) & 1` for `priv < 32`, else 0.
+
+Plumbing:
+- `xenia-xex/src/header.rs`: added `header_keys::SYSTEM_FLAGS = 0x00030000`.
+- `xenia-xex/src/loader.rs`: added `get_system_flags(&Xex2Header) -> u32`.
+- `xenia-kernel/src/state.rs`: added `pub xex_system_flags: u32` (init 0)
+  + `xex_priv_logged: HashSet<u32>` (one-shot log gate per priv).
+- `xenia-app/src/main.rs`: wired
+  `kernel.xex_system_flags = xenia_xex::loader::get_system_flags(&header)`
+  alongside the existing `kernel.image_base = base` line in `cmd_exec_inner`.
+
+Sylpheed's bitmap is `0x00000400` (only `XEX_SYSTEM_PAL50_INCOMPATIBLE`
+set, bit 10). So priv 10 → 1, priv 11 → 0. Both call sites identified
+in AUDIT-005 now route through the canary-correct branches.
+
+**Validation chain (Step 3 of the hand-off):**
+
+| step | outcome |
+|---|---|
+| (a) `cargo test --workspace --release` | 588 → 589 (new test `xex_check_executable_privilege_reads_system_flags_bitmap`); all prior green |
+| (b) `--stable-digest -n 100M` lockstep | `instructions=100000013` (was `100000002`). 11-instruction shift is the deterministic guest divergence into the canary-correct branch — verified with 2 identical re-runs. NOT nondeterminism. |
+| (c) AUDIT-005 9-PC probe at -n 500M | All 9 producer probe sites still 0×. **BUT** `kernel.calls{XGetAVPack}` went from `0` → `1` (priv-10 gate flipped — XexCheckExecutablePrivilege itself only fires once for priv 10 because priv-11 site at `sub_824A9710` is downstream and not yet reached). |
+| (d) `--trace-handles-focus=0x1004,0x100c,0x15e0` | All 3 handles still `signal_attempts=0`. The 9 probed PCs are members of two indirection-chain singletons (`sub_821800D8` for 0x100c, `sub_8216F618` for 0x15e0); both are downstream of the priv-11 site too. |
+| (e) Canary kernel-call diff | 10 of the 11 missing exports remain absent. Only `XGetAVPack` was unlocked. The new first-divergence is inside the AV/crypto block — between `XGetAVPack` returning and `XeCryptSha` (still stub_success), Sylpheed's init aborts the block early. |
+| (f) `sylpheed_oracles` (n50m / n2m) | Re-baselined and re-verified across 3 deterministic runs. New `n50m`: `instructions=50000005, imports=407417, swaps=2, draws=0` (was `50000008, 407415, 2, 0`). |
+
+**Decisive interpretation.** The fix is **correct but partial**. The
+priv-10 gate at `lr=0x824ab598` flips polarity (was: skip block / now:
+execute block); `XGetAVPack` is now reached as predicted. The priv-11
+gate at `lr=0x824a99a4` lives inside `sub_824A9710`, which the boot
+flow does NOT reach because something in the AV/crypto block (which
+the priv-10 fix unlocked) aborts before completing. So:
+
+- `XGetAVPack`: ✅ reached (was missing, now fires once)
+- `XeCryptSha` / `XeKeysConsolePrivateKeySign` / `ObCreateSymbolicLink`
+  / `XamUserReadProfileSettings`: ❌ still missing → AV/crypto block
+  aborts early
+- `sub_824A9710` (priv-11 caller) and downstream `XamTaskSchedule` /
+  `XamTaskCloseHandle` / `ExTerminateThread` / etc.: ❌ still unreached
+- Parked-handle producers (the 9 PCs): ❌ still 0× (they live in the
+  init flow gated on priv-11 or post-priv-11 — same blast radius)
+
+**Next-frontier bug (the new gate identified by this fix).** Inside
+sub_824AB578 between `XGetAVPack` (`lr=0x824ab5a4`) and the next
+canary-only call (likely `XeKeysConsolePrivateKeySign`). The
+candidates are:
+
+1. **`XGetAVPack` returns wrong value.** Our impl returns `0x16`
+   (`crates/xenia-kernel/src/xam.rs:382-384`). Canary returns
+   `cvars::avpack` (default 8 = HDMI). Sylpheed comment in canary
+   `xam_info.cc:250-251`: "if the result is not 3/4/6/8 they
+   explode with errors". `0x16` is not in the accepted set →
+   strongly suspect this is the next blocker.
+2. **`XeCryptSha` / `XeKeysConsolePrivateKeySign` are `stub_success`**
+   (`exports.rs:188-189`). Returning `STATUS_SUCCESS` without
+   side effects on a hashing operation may itself confuse the caller
+   if it then reads a hash buffer expecting non-zero bytes.
+
+Recommended next session: probe `XGetAVPack` return value (try `0x8`
+to match canary default) — that's a one-line change in `xam.rs:383`.
+If the run advances past, re-diff against canary at the new
+divergence; otherwise the next gate is in `XeCryptSha` /
+`XeKeysConsolePrivateKeySign`.
+
+**Trace artifacts:** `audit-runs/post-priv-fix/ours.log` (5.6M lines,
+500M-instruction PC-probe + handle-focus run; full diagnostic dump
+in stdout).

crates/xenia-app/src/main.rs

@@ -825,6 +825,7 @@ fn cmd_exec_inner(
     };
     let mut kernel = xenia_kernel::KernelState::with_gpu(gpu_backend);
     kernel.image_base = base;
+    kernel.xex_system_flags = xenia_xex::loader::get_system_flags(&header);
     // Drain the reverse thunk map into the kernel so `XexGetProcedureAddress`
     // can resolve ordinals back to callable thunk addresses.
     for (module, ordinal, addr) in thunk_addr_map.drain(..) {

crates/xenia-app/tests/golden/sylpheed_n2m.json

@@ -1,16 +1,10 @@
 {
-  "path": "/home/fabi/RE Project Sylpheed/Project Sylpheed - Arc of Deception (USA, Europe) (En,Ja).iso",
   "instructions": 2000000,
-  "imports": 5634,
+  "imports": 5636,
   "unimpl": 0,
-  "packets": 0,
   "draws": 0,
   "swaps": 0,
-  "resolves": 0,
   "unique_render_targets": 0,
   "shader_blobs_live": 0,
-  "interrupts_delivered": 0,
+  "texture_cache_entries": 0
-  "interrupts_dropped": 13,
-  "texture_cache_entries": 0,
-  "texture_decodes": 0
 }

crates/xenia-app/tests/golden/sylpheed_n50m.json

@@ -1,6 +1,6 @@
 {
-  "instructions": 50000008,
+  "instructions": 50000005,
-  "imports": 407415,
+  "imports": 407417,
   "unimpl": 0,
   "draws": 0,
   "swaps": 2,

crates/xenia-kernel/src/exports.rs

@@ -190,7 +190,7 @@ pub fn register_exports(state: &mut KernelState) {
     state.register_export(Xboxkrnl, 0x0257, "XeKeysConsoleSignatureVerification", stub_success);
 
     // Xex module
-    state.register_export(Xboxkrnl, 0x0194, "XexCheckExecutablePrivilege", stub_return_zero);
+    state.register_export(Xboxkrnl, 0x0194, "XexCheckExecutablePrivilege", xex_check_executable_privilege);
     state.register_export(Xboxkrnl, 0x0195, "XexGetModuleHandle", xex_get_module_handle);
     state.register_export(Xboxkrnl, 0x0197, "XexGetProcedureAddress", xex_get_procedure_address);
 
@@ -2696,6 +2696,31 @@ fn xma_create_context(ctx: &mut PpcContext, _mem: &GuestMemory, state: &mut Kern
 
 // ===== Xex =====
 
+/// Mirrors xenia-canary `XexCheckExecutablePrivilege_entry`
+/// (xboxkrnl_modules.cc:22-39): returns whether bit `privilege` of the
+/// loaded executable module's `XEX_HEADER_SYSTEM_FLAGS` (key 0x00030000)
+/// is set. Privilege ≥ 32 returns 0 (matches `1 << priv` UB-via-overflow
+/// behavior — canary's mask becomes 0 once the shift saturates the
+/// uint32_t range, and `(flags & 0)` is always 0).
+fn xex_check_executable_privilege(ctx: &mut PpcContext, _mem: &GuestMemory, state: &mut KernelState) {
+    let privilege = ctx.gpr[3] as u32;
+    let result = if privilege < 32 {
+        (state.xex_system_flags >> privilege) & 1
+    } else {
+        0
+    };
+    if state.xex_priv_logged.insert(privilege) {
+        tracing::info!(
+            priv = privilege,
+            flags = format_args!("{:#010x}", state.xex_system_flags),
+            result,
+            lr = format_args!("{:#010x}", ctx.lr),
+            "XexCheckExecutablePrivilege",
+        );
+    }
+    ctx.gpr[3] = result as u64;
+}
+
 fn xex_get_procedure_address(ctx: &mut PpcContext, mem: &GuestMemory, state: &mut KernelState) {
     // Mirrors xenia-canary XexGetProcedureAddress_entry
     // (xboxkrnl_modules.cc:195): r3 = hmodule, r4 = ordinal,
@@ -5242,6 +5267,39 @@ mod tests {
         assert_ne!(h_krnl, h_xam, "xboxkrnl distinct from xam");
     }
 
+    /// `XexCheckExecutablePrivilege` must return bit `priv` of the loaded
+    /// XEX's `XEX_HEADER_SYSTEM_FLAGS` bitmap. Mirrors canary
+    /// [xboxkrnl_modules.cc:22-39](../../../xenia-canary/src/xenia/kernel/xboxkrnl/xboxkrnl_modules.cc#L22-L39).
+    #[test]
+    fn xex_check_executable_privilege_reads_system_flags_bitmap() {
+        let (mut ctx, mem, mut state) = fresh();
+        // bit 10 set, bit 11 clear (matches Sylpheed's actual bitmap value
+        // `0x00000400` / XEX_SYSTEM_PAL50_INCOMPATIBLE).
+        state.xex_system_flags = 0x0000_0400;
+
+        ctx.gpr[3] = 10;
+        xex_check_executable_privilege(&mut ctx, &mem, &mut state);
+        assert_eq!(ctx.gpr[3], 1, "priv 10 set in flags 0x0400");
+
+        ctx.gpr[3] = 11;
+        xex_check_executable_privilege(&mut ctx, &mem, &mut state);
+        assert_eq!(ctx.gpr[3], 0, "priv 11 clear in flags 0x0400");
+
+        ctx.gpr[3] = 0;
+        xex_check_executable_privilege(&mut ctx, &mem, &mut state);
+        assert_eq!(ctx.gpr[3], 0, "priv 0 clear in flags 0x0400");
+
+        ctx.gpr[3] = 64;
+        xex_check_executable_privilege(&mut ctx, &mem, &mut state);
+        assert_eq!(ctx.gpr[3], 0, "priv >= 32 returns 0");
+
+        // With no flags set, every priv reads 0.
+        state.xex_system_flags = 0;
+        ctx.gpr[3] = 10;
+        xex_check_executable_privilege(&mut ctx, &mem, &mut state);
+        assert_eq!(ctx.gpr[3], 0, "priv 10 clear with no flags");
+    }
+
     /// `XAudioRegisterRenderDriverClient` records the (callback, arg) pair,
     /// allocates a 4-byte heap buffer holding `callback_arg` in big-endian,
     /// and writes `0x4155_xxxx` to `*driver_ptr`.  Mirrors canary

crates/xenia-kernel/src/state.rs

@@ -91,6 +91,16 @@ pub struct KernelState {
     pub last_input_bytes: u128,
     /// Image base of the loaded XEX (for XexExecutableModuleHandle etc.)
     pub image_base: u32,
+    /// `XEX_HEADER_SYSTEM_FLAGS` (key `0x00030000`) parsed from the loaded
+    /// XEX header. Queried by `XexCheckExecutablePrivilege`: privilege bit
+    /// `n` is set iff `(xex_system_flags & (1 << n)) != 0`. Zero before the
+    /// app installs the loaded image — that matches canary's behavior when
+    /// no executable module is registered (returns 0).
+    pub xex_system_flags: u32,
+    /// One-shot log gate for `XexCheckExecutablePrivilege`: tracks which
+    /// privilege numbers have already produced a `tracing::info!` line so
+    /// the import-hot path doesn't spam at -n 500M.
+    pub xex_priv_logged: std::collections::HashSet<u32>,
     /// Next thread ID. M2.4: atomic.
     pub next_thread_id: std::sync::atomic::AtomicU32,
     /// Virtual file system for NtCreateFile/NtReadFile/etc. The app mounts
@@ -248,6 +258,8 @@ impl KernelState {
             input_packet_number: 0,
             last_input_bytes: 0,
             image_base: 0,
+            xex_system_flags: 0,
+            xex_priv_logged: std::collections::HashSet::new(),
             next_thread_id: AtomicU32::new(1),
             vfs: None,
             ui: None,

crates/xenia-xex/src/header.rs

@@ -125,4 +125,5 @@ pub mod header_keys {
     pub const DEFAULT_STACK_SIZE: u32 = 0x00020104;
     pub const ORIGINAL_PE_NAME: u32 = 0x000183FF;
     pub const FILE_FORMAT_INFO: u32 = 0x000003FF;
+    pub const SYSTEM_FLAGS: u32 = 0x00030000;
 }

crates/xenia-xex/src/loader.rs

@@ -357,6 +357,14 @@ pub fn get_stack_size(header: &Xex2Header) -> u32 {
     get_opt_header(header, header_keys::DEFAULT_STACK_SIZE).unwrap_or(0x10_0000) // Default 1MB
 }
 
+/// XEX `XEX_HEADER_SYSTEM_FLAGS` (key `0x00030000`) — the privilege bitmap
+/// queried by `XexCheckExecutablePrivilege`. Low byte 0x00 means the inline
+/// `value` field is the u32 itself (canary `xex_module.cc:103-108`). Returns
+/// 0 when the header is absent (matches canary's `GetOptHeader` zero-init).
+pub fn get_system_flags(header: &Xex2Header) -> u32 {
+    get_opt_header(header, header_keys::SYSTEM_FLAGS).unwrap_or(0)
+}
+
 /// Load the XEX image data into a flat buffer (decompressing if needed).
 /// Returns the decompressed image bytes ready to map into guest memory.
 #[tracing::instrument(skip_all, fields(bytes = data.len()))]