Use Knobs to populate AppContext switches (#86883)

Previously AppContext switches were set by injecting a method that calls `AppContext.SetSwitch` at startup. Use the configuration blob added in #86068 instead. This makes startup a tiny bit faster and the outputs a tiny bit smaller.

Fixes #77054.

Author: MichalStrehovsky

src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.targets

@@ -214,12 +214,11 @@ The .NET Foundation licenses this file to you under the MIT license.
       <IlcArg Condition="'$(CustomNativeMain)' == 'true'" Include="--splitinit" />
       <IlcArg Condition="$(ExportsFile) != ''" Include="--exportsfile:$(ExportsFile)" />
       <IlcArg Include="@(AutoInitializedAssemblies->'--initassembly:%(Identity)')" />
-      <IlcArg Include="@(RuntimeHostConfigurationOption->'--appcontextswitch:%(Identity)=%(Value)')" />
-      <IlcArg Include="--appcontextswitch:RUNTIME_IDENTIFIER=$(RuntimeIdentifier)" />
       <IlcArg Include="@(DirectPInvoke->'--directpinvoke:%(Identity)')" />
       <IlcArg Include="@(DirectPInvokeList->'--directpinvokelist:%(Identity)')" />
       <IlcArg Include="@(_TrimmerFeatureSettings->'--feature:%(Identity)=%(Value)')" />
       <IlcArg Include="@(RuntimeHostConfigurationOption->'--runtimeknob:%(Identity)=%(Value)')" />
+      <IlcArg Include="--runtimeknob:RUNTIME_IDENTIFIER=$(RuntimeIdentifier)" />
       <IlcArg Condition="$(ServerGarbageCollection) == 'true'" Include="--runtimeopt:gcServer=1" />
       <IlcArg Condition="$(IlcGenerateCompleteTypeMetadata) == 'true' and $(IlcDisableReflection) != 'true'" Include="--completetypemetadata" />
       <IlcArg Condition="$(IlcGenerateStackTraceData) == 'true'" Include="--stacktracedata" />

src/coreclr/nativeaot/Runtime/MiscHelpers.cpp

@@ -38,6 +38,7 @@
 #include "GCMemoryHelpers.h"
 #include "GCMemoryHelpers.inl"
 #include "yieldprocessornormalized.h"
+#include "RhConfig.h"
 
 COOP_PINVOKE_HELPER(void, RhDebugBreak, ())
 {
@@ -422,6 +423,13 @@ COOP_PINVOKE_HELPER(int32_t, RhGetProcessCpuCount, ())
     return PalGetProcessCpuCount();
 }
 
+COOP_PINVOKE_HELPER(uint32_t, RhGetKnobValues, (char *** pResultKeys, char *** pResultValues))
+{
+    *pResultKeys = g_pRhConfig->GetKnobNames();
+    *pResultValues = g_pRhConfig->GetKnobValues();
+    return g_pRhConfig->GetKnobCount();
+}
+
 #if defined(TARGET_X86) || defined(TARGET_AMD64)
 EXTERN_C NATIVEAOT_API void __cdecl RhCpuIdEx(int* cpuInfo, int functionId, int subFunctionId)
 {

src/coreclr/nativeaot/Runtime/RhConfig.cpp

@@ -120,14 +120,8 @@ bool RhConfig::Environment::TryGetStringValue(const char* name, char** value)
     return true;
 }
 
-struct CompilerEmbeddedSettingsBlob
-{
-    uint32_t Size;
-    char Data[1];
-};
-
-extern "C" CompilerEmbeddedSettingsBlob g_compilerEmbeddedSettingsBlob;
-extern "C" CompilerEmbeddedSettingsBlob g_compilerEmbeddedKnobsBlob;
+extern "C" RhConfig::Config g_compilerEmbeddedSettingsBlob;
+extern "C" RhConfig::Config g_compilerEmbeddedKnobsBlob;
 
 bool RhConfig::ReadConfigValue(_In_z_ const char *name, uint64_t* pValue, bool decimal)
 {
@@ -136,7 +130,7 @@ bool RhConfig::ReadConfigValue(_In_z_ const char *name, uint64_t* pValue, bool d
 
     // Check the embedded configuration
     const char *embeddedValue = nullptr;
-    if (GetEmbeddedVariable(&g_embeddedSettings, &g_compilerEmbeddedSettingsBlob, name, true, &embeddedValue))
+    if (GetEmbeddedVariable(&g_compilerEmbeddedSettingsBlob, name, true, &embeddedValue))
     {
         *pValue = strtoull(embeddedValue, NULL, decimal ? 10 : 16);
         return true;
@@ -148,7 +142,7 @@ bool RhConfig::ReadConfigValue(_In_z_ const char *name, uint64_t* pValue, bool d
 bool RhConfig::ReadKnobUInt64Value(_In_z_ const char *name, uint64_t* pValue)
 {
     const char *embeddedValue = nullptr;
-    if (GetEmbeddedVariable(&g_embeddedKnobs, &g_compilerEmbeddedKnobsBlob, name, false, &embeddedValue))
+    if (GetEmbeddedVariable(&g_compilerEmbeddedKnobsBlob, name, false, &embeddedValue))
     {
         *pValue = strtoull(embeddedValue, NULL, 10);
         return true;
@@ -160,7 +154,7 @@ bool RhConfig::ReadKnobUInt64Value(_In_z_ const char *name, uint64_t* pValue)
 bool RhConfig::ReadKnobBooleanValue(_In_z_ const char *name, bool* pValue)
 {
     const char *embeddedValue = nullptr;
-    if (GetEmbeddedVariable(&g_embeddedKnobs, &g_compilerEmbeddedKnobsBlob, name, false, &embeddedValue))
+    if (GetEmbeddedVariable(&g_compilerEmbeddedKnobsBlob, name, false, &embeddedValue))
     {
         *pValue = strcmp(embeddedValue, "true") == 0;
         return true;
@@ -169,29 +163,30 @@ bool RhConfig::ReadKnobBooleanValue(_In_z_ const char *name, bool* pValue)
     return false;
 }
 
-bool RhConfig::GetEmbeddedVariable(void *volatile * embeddedSettings, void* compilerEmbeddedSettingsBlob, _In_z_ const char* configName, bool caseSensitive, _Out_ const char** configValue)
+char** RhConfig::GetKnobNames()
 {
-    // Read the config if we haven't yet
-    if (*embeddedSettings == NULL)
-    {
-        ReadEmbeddedSettings(embeddedSettings, compilerEmbeddedSettingsBlob);
-    }
+    return g_compilerEmbeddedKnobsBlob.GetKeys();
+}
 
-    // Config wasn't read or reading failed
-    if (*embeddedSettings == CONFIG_INI_NOT_AVAIL)
-    {
-        return false;
-    }
+char** RhConfig::GetKnobValues()
+{
+    return g_compilerEmbeddedKnobsBlob.GetValues();
+}
 
-    const ConfigPair* configPairs = (const ConfigPair*)*embeddedSettings;
+uint32_t RhConfig::GetKnobCount()
+{
+    return g_compilerEmbeddedKnobsBlob.GetCount();
+}
 
+bool RhConfig::GetEmbeddedVariable(Config* config, _In_z_ const char* configName, bool caseSensitive, _Out_ const char** configValue)
+{
     // Find the first name which matches
-    for (uint32_t iSettings = 0; iSettings < ((CompilerEmbeddedSettingsBlob*)compilerEmbeddedSettingsBlob)->Size; iSettings++)
+    for (uint32_t iSettings = 0; iSettings < config->GetCount(); iSettings++)
     {
-        if ((caseSensitive && strcmp(configName, configPairs[iSettings].Key) == 0)
-            || (!caseSensitive && _stricmp(configName, configPairs[iSettings].Key) == 0))
+        if ((caseSensitive && strcmp(configName, config->GetKeyAt(iSettings)) == 0)
+            || (!caseSensitive && _stricmp(configName, config->GetKeyAt(iSettings)) == 0))
         {
-            *configValue = configPairs[iSettings].Value;
+            *configValue = config->GetValueAt(iSettings);
             return true;
         }
     }
@@ -200,107 +195,4 @@ bool RhConfig::GetEmbeddedVariable(void *volatile * embeddedSettings, void* comp
     return false;
 }
 
-void RhConfig::ReadEmbeddedSettings(void *volatile * embeddedSettings, void* compilerEmbeddedSettingsBlob)
-{
-    if (*embeddedSettings == NULL)
-    {
-        uint32_t size = ((CompilerEmbeddedSettingsBlob*)compilerEmbeddedSettingsBlob)->Size;
-        char* data = ((CompilerEmbeddedSettingsBlob*)compilerEmbeddedSettingsBlob)->Data;
-
-        //if reading the file contents failed set embeddedSettings to CONFIG_INI_NOT_AVAIL
-        if (size == 0)
-        {
-            //only set if another thread hasn't initialized the buffer yet, otherwise ignore and let the first setter win
-            PalInterlockedCompareExchangePointer(embeddedSettings, CONFIG_INI_NOT_AVAIL, NULL);
-
-            return;
-        }
-
-        ConfigPair* iniBuff = new (nothrow) ConfigPair[size];
-        if (iniBuff == NULL)
-        {
-            //only set if another thread hasn't initialized the buffer yet, otherwise ignore and let the first setter win
-            PalInterlockedCompareExchangePointer(embeddedSettings, CONFIG_INI_NOT_AVAIL, NULL);
-
-            return;
-        }
-
-        uint32_t iBuff = 0;
-        uint32_t iIniBuff = 0;
-        char* currLine;
-
-        //while we haven't reached the max number of config pairs, or the end of the file, read the next line
-        while (iBuff < size)
-        {
-            currLine = &data[iBuff];
-
-            //find the end of the line
-            while ((data[iBuff] != '\0') && (iBuff < size))
-                iBuff++;
-
-            //parse the line
-            //only increment iIniBuff if the parsing succeeded otherwise reuse the config struct
-            if (ParseConfigLine(&iniBuff[iIniBuff], currLine))
-            {
-                iIniBuff++;
-            }
-
-            //advance to the next line;
-            iBuff++;
-        }
-
-        //if another thread initialized first let the first setter win
-        //delete the iniBuff to avoid leaking memory
-        if (PalInterlockedCompareExchangePointer(embeddedSettings, iniBuff, NULL) != NULL)
-        {
-            delete[] iniBuff;
-        }
-    }
-
-    return;
-}
-
-//Parses one line of config and populates values in the passed in configPair
-//returns: true if the parsing was successful, false if the parsing failed.
-//NOTE: if the method fails configPair is left in an uninitialized state
-bool RhConfig::ParseConfigLine(_Out_ ConfigPair* configPair, _In_z_ const char * line)
-{
-    uint32_t iLine = 0;
-    uint32_t iKey = 0;
-    uint32_t iVal = 0;
-
-    //while we haven't reached the end of the key signalled by '=', or the end of the line, or the key maxlen
-    while (line[iLine] != '=' && line[iLine] != '\0' && iKey < CONFIG_KEY_MAXLEN)
-    {
-        configPair->Key[iKey++] = line[iLine++];
-    }
-
-    //if the current char is not '=' we reached the key maxlen, or the line ended return false
-    if (line[iLine] != '=')
-    {
-        return FALSE;
-    }
-
-    configPair->Key[iKey] = '\0';
-
-    //increment to start of the value
-    iLine++;
-
-    //while we haven't reached the end of the line, or val maxlen
-    while (line[iLine] != '\0' && iVal < CONFIG_VAL_MAXLEN)
-    {
-        configPair->Value[iVal++] = line[iLine++];
-    }
-
-    //if the current char is not '\0' we didn't reach the end of the line return false
-    if (line[iLine] != '\0')
-    {
-        return FALSE;
-    }
-
-    configPair->Value[iVal] = '\0';
-
-    return TRUE;
-}
-
 #endif

src/coreclr/nativeaot/Runtime/RhConfig.h

@@ -18,26 +18,20 @@
 
 class RhConfig
 {
-
-#define CONFIG_INI_NOT_AVAIL (void*)0x1  //signal for ini file failed to load
-#define CONFIG_KEY_MAXLEN 50             //arbitrary max length of config keys increase if needed
 #define CONFIG_VAL_MAXLEN 16              //64 bit uint in hex
-private:
-    struct ConfigPair
+public:
+    struct Config
     {
+        uint32_t m_count;
+        char* m_first[];
     public:
-        char Key[CONFIG_KEY_MAXLEN + 1];  //maxlen + null terminator
-        char Value[CONFIG_VAL_MAXLEN + 1]; //maxlen + null terminator
+        uint32_t GetCount() { return m_count; }
+        char* GetKeyAt(int32_t index) { return m_first[index]; }
+        char* GetValueAt(int32_t index) { return m_first[m_count + index]; }
+        char** GetKeys() { return m_first; }
+        char** GetValues() { return &m_first[m_count]; }
     };
 
-    // g_embeddedSettings is a buffer of ConfigPair structs embedded in the compiled binary.
-    //
-    //NOTE: g_embeddedSettings is only set in ReadEmbeddedSettings and must be set atomically only once
-    //      using PalInterlockedCompareExchangePointer to avoid races when initializing
-    void* volatile g_embeddedSettings = NULL;
-    void* volatile g_embeddedKnobs = NULL;
-
-public:
     class Environment
     {
     public: // static
@@ -52,6 +46,10 @@ class RhConfig
     bool ReadKnobUInt64Value(_In_z_ const char* wszName, uint64_t* pValue);
     bool ReadKnobBooleanValue(_In_z_ const char* wszName, bool* pValue);
 
+    char** GetKnobNames();
+    char** GetKnobValues();
+    uint32_t GetKnobCount();
+
 #define DEFINE_VALUE_ACCESSOR(_name, defaultVal)        \
     uint64_t Get##_name()                                 \
     {                                                   \
@@ -99,16 +97,9 @@ class RhConfig
 #define CONFIG_FILE_MAXLEN RCV_Count * sizeof(ConfigPair) + 2000
 
 private:
-    //Parses one line of config and populates values in the passed in configPair
-    //returns: true if the parsing was successful, false if the parsing failed.
-    //NOTE: if the method fails configPair is left in an uninitialized state
-    bool ParseConfigLine(_Out_ ConfigPair* configPair, _In_z_ const char * line);
-
-    void ReadEmbeddedSettings(void *volatile * embeddedSettings, void* compilerEmbeddedSettingsBlob);
-
     // Gets a pointer to the embedded configuration value. Memory is held by the callee.
     // Returns true if the variable was found, false otherwise
-    bool GetEmbeddedVariable(void *volatile * embeddedSettings, void* compilerEmbeddedSettingsBlob, _In_z_ const char* configName, bool caseSensitive, _Out_ const char** configValue);
+    bool GetEmbeddedVariable(Config* config, _In_z_ const char* configName, bool caseSensitive, _Out_ const char** configValue);
 
     uint32_t  m_uiConfigValuesRead;
     uint64_t  m_uiConfigValues[RCV_Count];

src/coreclr/nativeaot/System.Private.CoreLib/src/System/AppContext.NativeAot.cs

@@ -1,13 +1,30 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Collections.Generic;
 using System.Runtime;
 using System.Runtime.ExceptionServices;
+using System.Text;
 
 namespace System
 {
     public static partial class AppContext
     {
+        private static unsafe Dictionary<string, object?> InitializeDataStore()
+        {
+            uint count = RuntimeImports.RhGetKnobValues(out byte** keys, out byte** values);
+
+            var dataStore = new Dictionary<string, object?>((int)count);
+            for (int i = 0; i < count; i++)
+            {
+                dataStore.Add(
+                    Encoding.UTF8.GetString(keys[i], string.strlen(keys[i])),
+                    Encoding.UTF8.GetString(values[i], string.strlen(values[i])));
+            }
+
+            return dataStore;
+        }
+
         [RuntimeExport("OnFirstChanceException")]
         internal static void OnFirstChanceException(object e)
         {

src/coreclr/nativeaot/System.Private.CoreLib/src/System/Runtime/RuntimeImports.cs

@@ -553,6 +553,10 @@ internal static IntPtr RhGetModuleSection(TypeManagerHandle module, ReadyToRunSe
         [RuntimeImport(RuntimeLibrary, "RhGetLoadedOSModules")]
         internal static extern uint RhGetLoadedOSModules(IntPtr[] resultArray);
 
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        [RuntimeImport(RuntimeLibrary, "RhGetKnobValues")]
+        internal static extern unsafe uint RhGetKnobValues(out byte** keyArray, out byte** valueArray);
+
         [MethodImplAttribute(MethodImplOptions.InternalCall)]
         [RuntimeImport(RuntimeLibrary, "RhGetOSModuleFromPointer")]
         internal static extern IntPtr RhGetOSModuleFromPointer(IntPtr pointerVal);