ud-emulator 0.1.4

//! `advapi32.dll` stubs — round-8 surface for IR50_32.DLL.
//!
//! IR50 imports the registry API to enumerate codec-specific keys
//! (`HKLM\SOFTWARE\Intel\Indeo Video 5\…`). The decode pipeline
//! does not actually depend on registry data — codecs use
//! it for per-machine bandwidth / quality tuning that the
//! decode body has fall-back defaults for.
//!
//! Every stub returns the canonical "no key / no value" result
//! so the codec falls into its hard-coded default path.
//!
//! Reference: MSDN "Registry Functions" —
//! `https://learn.microsoft.com/en-us/windows/win32/api/winreg/`.

use super::{arg_dword, read_cstr_local, HostState, Registry, StubFn, Win32Error};
use crate::emulator::{Cpu, Mmu};

// winerror.h: common return codes.
const ERROR_FILE_NOT_FOUND: u32 = 2;
const ERROR_SUCCESS: u32 = 0;

// HKEY value handed back to callers (bare-bones; the sandbox
// doesn't model a real registry). Non-zero so RAII guards in
// the codec proceed.
const HKEY_FPU: u32 = 0xC0DE_F0F0;

/// True iff `subkey` (case-insensitive) names a registry path
/// that real Win9x/NT machines unconditionally have.
///
/// Round 20 — the Indeo IR41/IR50 DRV_LOAD-time CPUID block
/// AND-gates its "use MMX kernels" decision flag (`[0x1c4a9a38]`)
/// with `[ebp-8]`, which is set to 1 iff
/// `RegOpenKeyExA(HKLM, "HARDWARE\DESCRIPTION\System\FloatingPointProcessor", ...)`
/// succeeded. Real Indeo machines (anything Win95 SP1+ on a
/// real x86) always have that key; without success, the
/// codec falls back to the integer-only kernels and our test
/// pipeline reports `mmx_dispatch_count = 0` even though
/// every preceding precondition (CPUID, EFLAGS.ID, MMX bit)
/// is correct.
///
/// Returning ERROR_SUCCESS for this exact path (and the
/// well-known FloatingPointProcessor\0..\0N child enumeration
/// any FPU-checking caller might walk) lets the gate close
/// cleanly. Codecs that genuinely needed the registry data
/// (the codec's RegQueryValueExA path returns
/// ERROR_FILE_NOT_FOUND, so callers fall through to defaults)
/// are unaffected.
fn key_exists_synthetically(subkey: &str) -> bool {
    let s = subkey.to_ascii_lowercase();
    // Trim leading slashes some callers prepend.
    let s = s.trim_start_matches('\\');
    s == "hardware\\description\\system\\floatingpointprocessor"
        || s.starts_with("hardware\\description\\system\\floatingpointprocessor\\")
}

/// Register every advapi32 stub.
pub fn register(registry: &mut Registry) {
    registry.register(
        "advapi32.dll",
        "RegCloseKey",
        stub_reg_close_key as StubFn,
        1,
    );
    registry.register(
        "advapi32.dll",
        "RegCreateKeyA",
        stub_reg_create_key as StubFn,
        3,
    );
    registry.register(
        "advapi32.dll",
        "RegCreateKeyExA",
        stub_reg_create_key_ex as StubFn,
        9,
    );
    registry.register(
        "advapi32.dll",
        "RegDeleteKeyA",
        stub_reg_delete as StubFn,
        2,
    );
    registry.register(
        "advapi32.dll",
        "RegDeleteValueA",
        stub_reg_delete as StubFn,
        2,
    );
    registry.register(
        "advapi32.dll",
        "RegEnumKeyExA",
        stub_reg_enum_key_ex_a as StubFn,
        8,
    );
    registry.register(
        "advapi32.dll",
        "RegOpenKeyA",
        stub_reg_open_key_a as StubFn,
        3,
    );
    registry.register(
        "advapi32.dll",
        "RegOpenKeyExA",
        stub_reg_open_key_ex_a as StubFn,
        5,
    );
    registry.register(
        "advapi32.dll",
        "RegQueryValueA",
        stub_reg_query_value as StubFn,
        4,
    );
    registry.register(
        "advapi32.dll",
        "RegQueryValueExA",
        stub_reg_query_value_ex as StubFn,
        6,
    );
    registry.register(
        "advapi32.dll",
        "RegSetValueA",
        stub_reg_set_value as StubFn,
        5,
    );
    registry.register(
        "advapi32.dll",
        "RegSetValueExA",
        stub_reg_set_value as StubFn,
        6,
    );
}

/// `LSTATUS RegCloseKey(HKEY)`. Always succeeds.
fn stub_reg_close_key(
    _cpu: &mut Cpu,
    _mmu: &mut Mmu,
    _state: &mut HostState,
    _registry: &Registry,
) -> Result<u32, Win32Error> {
    Ok(ERROR_SUCCESS)
}

/// `LSTATUS RegCreateKeyA(HKEY hKey, LPCSTR lpSubKey, PHKEY
/// phkResult)`. Pretend the key exists; write a non-zero handle
/// to `phkResult` so RAII wrappers proceed.
fn stub_reg_create_key(
    cpu: &mut Cpu,
    mmu: &mut Mmu,
    _state: &mut HostState,
    _registry: &Registry,
) -> Result<u32, Win32Error> {
    let _hkey = arg_dword(cpu, mmu, 0).map_err(|t| trap("RegCreateKeyA", t))?;
    let _sub = arg_dword(cpu, mmu, 1).map_err(|t| trap("RegCreateKeyA", t))?;
    let phk = arg_dword(cpu, mmu, 2).map_err(|t| trap("RegCreateKeyA", t))?;
    if phk != 0 {
        let _ = mmu.store32(phk, 0xC0DE_8E0F);
    }
    Ok(ERROR_SUCCESS)
}

/// `LSTATUS RegCreateKeyExA(...)`. Same outcome as RegCreateKeyA.
fn stub_reg_create_key_ex(
    cpu: &mut Cpu,
    mmu: &mut Mmu,
    _state: &mut HostState,
    _registry: &Registry,
) -> Result<u32, Win32Error> {
    let phk = arg_dword(cpu, mmu, 6).map_err(|t| trap("RegCreateKeyExA", t))?;
    if phk != 0 {
        let _ = mmu.store32(phk, 0xC0DE_8E0F);
    }
    let disposition = arg_dword(cpu, mmu, 7).map_err(|t| trap("RegCreateKeyExA", t))?;
    if disposition != 0 {
        // REG_OPENED_EXISTING_KEY = 2
        let _ = mmu.store32(disposition, 2);
    }
    Ok(ERROR_SUCCESS)
}

/// `LSTATUS RegDeleteKeyA / RegDeleteValueA(...)`. No-op success.
fn stub_reg_delete(
    _cpu: &mut Cpu,
    _mmu: &mut Mmu,
    _state: &mut HostState,
    _registry: &Registry,
) -> Result<u32, Win32Error> {
    Ok(ERROR_SUCCESS)
}

/// `LSTATUS RegEnumKeyExA(...)`. Return ERROR_NO_MORE_ITEMS = 259
/// on first call so codecs that iterate registry sub-keys exit
/// cleanly.
fn stub_reg_enum_key_ex_a(
    _cpu: &mut Cpu,
    _mmu: &mut Mmu,
    _state: &mut HostState,
    _registry: &Registry,
) -> Result<u32, Win32Error> {
    const ERROR_NO_MORE_ITEMS: u32 = 259;
    Ok(ERROR_NO_MORE_ITEMS)
}

/// `LSTATUS RegOpenKeyA(HKEY, LPCSTR lpSubKey, PHKEY phkResult)`.
/// For paths every real Windows machine has (see
/// [`key_exists_synthetically`]), return ERROR_SUCCESS with a
/// non-zero pseudo-handle so callers proceed; otherwise return
/// ERROR_FILE_NOT_FOUND so the codec falls back to its defaults.
fn stub_reg_open_key_a(
    cpu: &mut Cpu,
    mmu: &mut Mmu,
    _state: &mut HostState,
    _registry: &Registry,
) -> Result<u32, Win32Error> {
    let _hkey = arg_dword(cpu, mmu, 0).map_err(|t| trap("RegOpenKeyA", t))?;
    let p_sub = arg_dword(cpu, mmu, 1).map_err(|t| trap("RegOpenKeyA", t))?;
    let phk = arg_dword(cpu, mmu, 2).map_err(|t| trap("RegOpenKeyA", t))?;
    let sub = if p_sub != 0 {
        read_cstr_local(mmu, p_sub, 1024).unwrap_or_default()
    } else {
        String::new()
    };
    if key_exists_synthetically(&sub) {
        if phk != 0 {
            let _ = mmu.store32(phk, HKEY_FPU);
        }
        return Ok(ERROR_SUCCESS);
    }
    if phk != 0 {
        let _ = mmu.store32(phk, 0);
    }
    Ok(ERROR_FILE_NOT_FOUND)
}

/// `LSTATUS RegOpenKeyExA(HKEY hKey, LPCSTR lpSubKey,
/// DWORD ulOptions, REGSAM samDesired, PHKEY phkResult)`. Same
/// matching as `RegOpenKeyA` — only the synthetically-present
/// well-known paths return ERROR_SUCCESS.
fn stub_reg_open_key_ex_a(
    cpu: &mut Cpu,
    mmu: &mut Mmu,
    _state: &mut HostState,
    _registry: &Registry,
) -> Result<u32, Win32Error> {
    let _hkey = arg_dword(cpu, mmu, 0).map_err(|t| trap("RegOpenKeyExA", t))?;
    let p_sub = arg_dword(cpu, mmu, 1).map_err(|t| trap("RegOpenKeyExA", t))?;
    let _opts = arg_dword(cpu, mmu, 2).map_err(|t| trap("RegOpenKeyExA", t))?;
    let _sam = arg_dword(cpu, mmu, 3).map_err(|t| trap("RegOpenKeyExA", t))?;
    let phk = arg_dword(cpu, mmu, 4).map_err(|t| trap("RegOpenKeyExA", t))?;
    let sub = if p_sub != 0 {
        read_cstr_local(mmu, p_sub, 1024).unwrap_or_default()
    } else {
        String::new()
    };
    if key_exists_synthetically(&sub) {
        if phk != 0 {
            let _ = mmu.store32(phk, HKEY_FPU);
        }
        return Ok(ERROR_SUCCESS);
    }
    if phk != 0 {
        let _ = mmu.store32(phk, 0);
    }
    Ok(ERROR_FILE_NOT_FOUND)
}

/// `LSTATUS RegQueryValueA(...)`. Return ERROR_FILE_NOT_FOUND.
fn stub_reg_query_value(
    _cpu: &mut Cpu,
    _mmu: &mut Mmu,
    _state: &mut HostState,
    _registry: &Registry,
) -> Result<u32, Win32Error> {
    Ok(ERROR_FILE_NOT_FOUND)
}

/// `LSTATUS RegQueryValueExA(HKEY, LPCSTR lpValueName, LPDWORD
/// lpReserved, LPDWORD lpType, LPBYTE lpData, LPDWORD lpcbData)`.
/// Return ERROR_FILE_NOT_FOUND with cb = 0 so callers see "no
/// data".
fn stub_reg_query_value_ex(
    cpu: &mut Cpu,
    mmu: &mut Mmu,
    _state: &mut HostState,
    _registry: &Registry,
) -> Result<u32, Win32Error> {
    let pcb = arg_dword(cpu, mmu, 5).map_err(|t| trap("RegQueryValueExA", t))?;
    if pcb != 0 {
        let _ = mmu.store32(pcb, 0);
    }
    Ok(ERROR_FILE_NOT_FOUND)
}

/// `LSTATUS RegSetValueA / RegSetValueExA(...)`. No-op success.
fn stub_reg_set_value(
    _cpu: &mut Cpu,
    _mmu: &mut Mmu,
    _state: &mut HostState,
    _registry: &Registry,
) -> Result<u32, Win32Error> {
    Ok(ERROR_SUCCESS)
}

fn trap(stub: &'static str, t: crate::emulator::Trap) -> Win32Error {
    Win32Error::InvalidArgument {
        stub,
        reason: format!("{t}"),
    }
}