driver: look up registry redirects at PASSIVE_LEVEL

SarTest/SarTest.cpp

@@ -68,6 +68,7 @@ int usage()
         "                --id-prefix <id> (endpoint IDs; default: the name prefix)\n"
         "Other options:  --results <file.json> --phase-timeout S --no-sarasio-log\n"
         "                --keep-config (host/run: do not rewrite default.json)\n"
+        "                --app-routing (turn on application routing in default.json)\n"
         "                --registered (use the COM-registered SarAsio instead of a path)\n"
         "                --wait S --wait-gone S --restart-delay MS --rate HZ\n"
         "                --min-valid RATIO --max-discontinuities N\n"
@@ -145,7 +146,7 @@ bool prepareConfig(const Args& args, const EndpointLayout& layout,
     }
 
     if (!writeDriverConfig(layout, driverClsid,
-        args.getInt(L"wavert-min-frames", 0), path)) {
+        args.getInt(L"wavert-min-frames", 0), path, args.has(L"app-routing"))) {
         return false;
     }
 
@@ -211,7 +212,7 @@ int cmdConfig(const Args& args)
     std::wstring out = args.get(L"out", configurationPath().c_str());
 
     if (!writeDriverConfig(layout, SAR_TEST_CLOCK_CLSID_STR,
-        args.getInt(L"wavert-min-frames", 0), out)) {
+        args.getInt(L"wavert-min-frames", 0), out, args.has(L"app-routing"))) {
         return 1;
     }
 

SarTest/install.cpp

@@ -58,7 +58,8 @@ std::wstring loggingPath()
 
 bool writeDriverConfig(
     const EndpointLayout& layout, const std::wstring& driverClsid,
-    int waveRtMinimumFrames, const std::wstring& path)
+    int waveRtMinimumFrames, const std::wstring& path,
+    bool applicationRouting)
 {
     std::vector<std::string> endpoints;
 
@@ -80,7 +81,7 @@ bool writeDriverConfig(
     JsonObject root;
 
     root.setString("driverClsid", narrow(driverClsid))
-        .setBool("enableApplicationRouting", false)
+        .setBool("enableApplicationRouting", applicationRouting)
         .setInt("waveRtMinimumFrames", waveRtMinimumFrames)
         .setRaw("endpoints", jsonArray(endpoints))
         .setRaw("applications", "[]");

SarTest/install.h

@@ -28,10 +28,12 @@ std::wstring configurationPath();
 std::wstring loggingPath();
 
 // Writes a SarAsio default.json describing the layout, with the given ASIO
-// driver CLSID as the physical interface and application routing disabled.
+// driver CLSID as the physical interface. Application routing (no rules, so
+// only the redirection of the audio device enumerator) is off unless asked.
 bool writeDriverConfig(
     const EndpointLayout& layout, const std::wstring& driverClsid,
-    int waveRtMinimumFrames, const std::wstring& path);
+    int waveRtMinimumFrames, const std::wstring& path,
+    bool applicationRouting = false);
 
 // Software device node for the SAR driver, matching the INF's hardware ID.
 bool deviceNodeExists();

SynchronousAudioRouter/entry.cpp

@@ -718,7 +718,6 @@ NTSTATUS SarIrpDeviceControl(PDEVICE_OBJECT deviceObject, PIRP irp)
 VOID SarUnload(PDRIVER_OBJECT driverObject)
 {
     SAR_INFO("SAR is unloading");
-    KIRQL irql;
     SarDriverExtension *extension =
         (SarDriverExtension *)IoGetDriverObjectExtension(
             driverObject, DriverEntry);
@@ -731,12 +730,15 @@ VOID SarUnload(PDRIVER_OBJECT driverObject)
         CmUnRegisterCallback(extension->filterCookie);
     }
 
-    irql = ExAcquireSpinLockExclusive(&extension->registryRedirectLock);
+    KeEnterCriticalRegion();
+    ExAcquireResourceExclusiveLite(&extension->registryRedirectLock, TRUE);
     SarClearStringTable(
         &extension->registryRedirectTableWow64, SarDeleteRegistryRedirect);
     SarClearStringTable(
         &extension->registryRedirectTable, SarDeleteRegistryRedirect);
-    ExReleaseSpinLockExclusive(&extension->registryRedirectLock, irql);
+    ExReleaseResourceLite(&extension->registryRedirectLock);
+    KeLeaveCriticalRegion();
+    ExDeleteResourceLite(&extension->registryRedirectLock);
 
     if (extension->filterUser) {
         // Allocated by SeQueryInformationToken
@@ -768,9 +770,6 @@ BOOL SarFilterMatchesPath(
 {
     PRTL_AVL_TABLE table = &extension->registryRedirectTable;
     PVOID entry = nullptr;
-    KIRQL irql;
-    UNICODE_STRING nonpagedPath;
-    NTSTATUS status = STATUS_SUCCESS;
 
     if (!path) {
         return FALSE;
@@ -782,24 +781,20 @@ BOOL SarFilterMatchesPath(
     }
 #endif
 
-    // TODO: we get a path that's in paged memory from the configuration manager
-    // so we can't access it with IRQL raised to dispatch level by the spinlock.
-    // Probably better to just use an ERESOURCE or something here instead.
-    status = SarStringDuplicate(&nonpagedPath, path);
-
-    if (!NT_SUCCESS(status)) {
-        return FALSE;
-    }
-
-    irql = ExAcquireSpinLockShared(&extension->registryRedirectLock);
-    entry = SarGetStringTableEntry(table, &nonpagedPath);
+    // Stay at PASSIVE_LEVEL: the path from the configuration manager is in
+    // paged memory and the table's string comparison is pageable code. Under
+    // a spin lock this bugchecked (IRQL_NOT_LESS_OR_EQUAL) whenever that code
+    // was paged out.
+    KeEnterCriticalRegion();
+    ExAcquireResourceSharedLite(&extension->registryRedirectLock, TRUE);
+    entry = SarGetStringTableEntry(table, path);
 
     if (entry) {
         *redirectPath = *(PCUNICODE_STRING)entry;
     }
 
-    ExReleaseSpinLockShared(&extension->registryRedirectLock, irql);
-    SarStringFree(&nonpagedPath);
+    ExReleaseResourceLite(&extension->registryRedirectLock);
+    KeLeaveCriticalRegion();
     return entry != nullptr;
 }
 
@@ -1129,6 +1124,7 @@ extern "C" NTSTATUS DriverEntry(
 
     RtlZeroMemory(extension, sizeof(SarDriverExtension));
     ExInitializeFastMutex(&extension->mutex);
+    ExInitializeResourceLite(&extension->registryRedirectLock);
     SarInitializeTable(&extension->controlContextTable);
     SarInitializeStringTable(&extension->registryRedirectTableWow64);
     SarInitializeStringTable(&extension->registryRedirectTable);

SynchronousAudioRouter/sar.h

@@ -210,11 +210,12 @@ typedef struct SarDriverExtension
     // This shouldn't really be needed as long as CmUnRegisterCallback can't
     // complete while one of our callback routines is still running, but there
     // is no explicit documentation of that, so we protect the registry redirect
-    // tables with a reader writer spinlock "just in case." Note that
+    // tables with a reader writer lock "just in case." Note that
     // RTL_AVL_TABLE is used here instead of RTL_GENERIC_TABLE to avoid
-    // splaying which would be unsafe with a read-only lock. All related
-    // structures must be in nonpaged memory.
-    EX_SPIN_LOCK registryRedirectLock;
+    // splaying which would be unsafe with a read-only lock. It is a resource,
+    // not a spin lock: lookups compare strings with RtlCompareUnicodeString,
+    // which is pageable, and the registry callback runs at PASSIVE_LEVEL.
+    ERESOURCE registryRedirectLock;
     RTL_AVL_TABLE registryRedirectTableWow64;
     RTL_AVL_TABLE registryRedirectTable;
     LARGE_INTEGER filterCookie;

tools/test/Invoke-SarTest.ps1

@@ -109,6 +109,16 @@ function Invoke-Scenario {
     return $record
 }
 
+# Registers or unregisters SarAsio's COM classes. The driver's application
+# routing only redirects to SarAsio when they are registered.
+function Set-SarAsioRegistered {
+    param([bool]$Registered)
+
+    $regArgs = @('/s') + $(if ($Registered) { @() } else { @('/u') }) + @("`"$sarAsio`"")
+    $proc = Start-Process regsvr32.exe -ArgumentList $regArgs -Wait -PassThru
+    if ($proc.ExitCode -ne 0) { Write-Warning "regsvr32 $($regArgs -join ' ') exited with $($proc.ExitCode)" }
+}
+
 # Windows Server images ship with the audio stack disabled.
 foreach ($service in 'AudioEndpointBuilder', 'Audiosrv') {
     try {
@@ -146,7 +156,7 @@ if (-not $SkipInstall) {
 $common = @('--sarasio', "`"$sarAsio`"", '--channels', $Channels)
 
 if ($Scenarios -contains 'issues') {
-    # Regression checks for specific GitHub issues, one short host each.
+    # Regression checks, one short host each, most for a GitHub issue.
     $summary.scenarios += Invoke-Scenario 'issue-133-control-panel' (
         @('control-panel', '--endpoints', 1) + $common) -Timeout 120
     $summary.scenarios += Invoke-Scenario 'issue-54-no-interface' (
@@ -158,6 +168,14 @@ if ($Scenarios -contains 'issues') {
     $summary.scenarios += Invoke-Scenario 'long-endpoint-name' (
         @('host', '--endpoints', 1, '--duration', 2, '--id-prefix', 'SarTest-long',
           '--prefix', ('SarTestLongEndpointName' * 4)) + $common) -Timeout 120
+    # Application routing on: from then on the driver's registry filter sees
+    # every registry value query on the machine. With SarAsio's COM classes
+    # registered, the harness's own WASAPI client also goes through SarAsio's
+    # device enumerator wrapper.
+    Set-SarAsioRegistered $true
+    $summary.scenarios += Invoke-Scenario 'app-routing' (
+        @('run', '--endpoints', 1, '--iterations', 1, '--duration', $Duration, '--app-routing') + $common)
+    Set-SarAsioRegistered $false
 }
 
 if ($Scenarios -contains 'matrix') {

tools/test/README.md

@@ -92,7 +92,9 @@ configured and checks that it still offers a stereo input and output.
 then gives it a new ID, and checks that the new ID shows the new name; the
 results record what Windows shows for the reused ID. `long-endpoint-name`
 runs a host whose endpoint names are longer than the driver's 63-character
-limit.
+limit. `app-routing` runs a loopback with application routing on and
+SarAsio's COM classes registered, which turns on the driver's registry
+filter.
 `Invoke-SarTest.ps1 -Scenarios` selects any of `issues`, `matrix`, `race`
 and `kill`.