Identify OSArchitecture at run-time

src/coreclr/pal/inc/rt/ntimage.h

@@ -2,6 +2,9 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 //
 
+// This file is a verbatim copy of the Windows OS header with PE file structure definitions.
+
+
 //
 // ===========================================================================
 // File: ntimage.h

src/libraries/Common/src/Interop/Unix/System.Native/Interop.GetOSArchitecture.cs

@@ -1,7 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

@@ -885,7 +885,6 @@
     <Compile Include="$(MSBuildThisFileDirectory)System\Runtime\InteropServices\PreserveSigAttribute.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Runtime\InteropServices\ProgIdAttribute.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Runtime\InteropServices\RuntimeInformation.cs" />
-    <Compile Include="$(MSBuildThisFileDirectory)System\Runtime\InteropServices\RuntimeInformation.ProcessArchitecture.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Runtime\InteropServices\SafeArrayRankMismatchException.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Runtime\InteropServices\SafeArrayTypeMismatchException.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Runtime\InteropServices\SafeBuffer.cs" />

src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/RuntimeInformation.Windows.cs

@@ -31,25 +31,44 @@ public static string OSDescription
             }
         }
 
-        public static Architecture OSArchitecture
+        public static unsafe Architecture OSArchitecture
         {
             get
             {
                 int osArch = s_osArchPlusOne - 1;
 
                 if (osArch < 0)
                 {
-                    Interop.Kernel32.SYSTEM_INFO sysInfo;
-                    unsafe
+                    // If we are running an x64 process on a non-x64 windows machine, we will report x64 as OS architecutre.
+                    //
+                    // IsWow64Process2 is only available on Windows 10+, so we will perform run-time introspection via indirect load
+                    if (NativeLibrary.TryGetExport(NativeLibrary.Load(Interop.Libraries.Kernel32), "IsWow64Process2", out IntPtr isWow64Process2Ptr))
                     {
+                        ushort processMachine, nativeMachine;
+                        var isWow64Process2 = (delegate* unmanaged<IntPtr, ushort*, ushort*, int>)isWow64Process2Ptr;
+                        if (isWow64Process2(Interop.Kernel32.GetCurrentProcess(), &processMachine, &nativeMachine) != 0)
+                        {
+                            osArch = (int)MapMachineConstant(nativeMachine);
+                        }
+                        else
+                        {
+                            Debug.Fail("Call to IsWow64Process2() failed unexpectedly. Falling back to ProcessArchitecture");
+                            osArch = (int)ProcessArchitecture;
+                        }
+                    }
+                    else
+                    {
+                        Interop.Kernel32.SYSTEM_INFO sysInfo;
                         Interop.Kernel32.GetNativeSystemInfo(&sysInfo);
+
+                        osArch = (int)Map(sysInfo.wProcessorArchitecture);
                     }
-                    osArch = (int)Map(sysInfo.wProcessorArchitecture);
 
                     s_osArchPlusOne = osArch + 1;
+
+                    Debug.Assert(osArch >= 0);
                 }
 
-                Debug.Assert(osArch >= 0);
                 return (Architecture)osArch;
             }
         }
@@ -70,5 +89,27 @@ private static Architecture Map(int processorArchitecture)
                     return Architecture.X86;
             }
         }
+
+        private static Architecture MapMachineConstant(ushort processMachine)
+        {
+            switch (processMachine)
+            {
+                case 0x01C4: // IMAGE_FILE_MACHINE_ARMNT
+                    return Architecture.Arm;
+
+                case 0x8664: // IMAGE_FILE_MACHINE_AMD64
+                    return Architecture.X64;
+
+                case 0xAA64: // IMAGE_FILE_MACHINE_ARM64
+                    return Architecture.Arm64;
+
+                case 0x014C: // IMAGE_FILE_MACHINE_I386
+                    return Architecture.X86;
+
+                default: // IMAGE_FILE_MACHINE_UNKNOWN etc.
+                    Debug.Fail("Unidentified OS Architecture. Falling back to ProcessArchitecture");
+                    return ProcessArchitecture;
+            }
+        }
     }
 }

src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/RuntimeInformation.cs

@@ -50,5 +50,26 @@ public static string FrameworkDescription
         /// Indicates whether the current application is running on the specified platform.
         /// </summary>
         public static bool IsOSPlatform(OSPlatform osPlatform) => OperatingSystem.IsOSPlatform(osPlatform.Name);
+
+        public static Architecture ProcessArchitecture
+#if TARGET_X86
+            => Architecture.X86;
+#elif TARGET_AMD64
+            => Architecture.X64;
+#elif TARGET_ARMV6
+            => Architecture.Armv6;
+#elif TARGET_ARM
+            => Architecture.Arm;
+#elif TARGET_ARM64
+            => Architecture.Arm64;
+#elif TARGET_WASM
+            => Architecture.Wasm;
+#elif TARGET_S390X
+            => Architecture.S390x;
+#elif TARGET_LOONGARCH64
+            => Architecture.LoongArch64;
+#else
+#error Unknown Architecture
+#endif
     }
 }

src/native/libs/System.Native/pal_runtimeinformation.c

@@ -4,11 +4,16 @@
 #include "pal_config.h"
 #include "pal_runtimeinformation.h"
 #include "pal_types.h"
+#include <assert.h>
 #include <stdio.h>
 #include <string.h>
 #include <sys/utsname.h>
 #if defined(TARGET_ANDROID)
 #include <sys/system_properties.h>
+#elif defined(TARGET_OSX)
+#include <sys/sysctl.h>
+#elif defined(TARGET_SUNOS)
+#include <sys/systeminfo.h>
 #endif
 
 char* SystemNative_GetUnixRelease()
@@ -48,8 +53,89 @@ int32_t SystemNative_GetUnixVersion(char* version, int* capacity)
     return 0;
 }
 
-/* Returns an int representing the OS Architecture. -1 if same as process architecture. */
+// Keep in sync with System.Runtime.InteropServices.Architecture enum
+enum
+{
+    ARCH_X86,
+    ARCH_X64,
+    ARCH_ARM,
+    ARCH_ARM64,
+    ARCH_WASM,
+    ARCH_S390X,
+    ARCH_LOONGARCH64,
+    ARCH_ARMV6,
+};
+
 int32_t SystemNative_GetOSArchitecture()
 {
-    return -1;
+#ifdef TARGET_WASM
+    return ARCH_WASM;
+#else
+    int32_t result = -1;
+#ifdef TARGET_SUNOS
+    // On illumos/Solaris, the recommended way to obtain machine
+    // architecture is using `sysinfo` rather than `utsname.machine`.
+
+    char isa[32];
+    if (sysinfo(SI_ARCHITECTURE_K, isa, sizeof(isa)) > -1)
+    {
+#else
+    struct utsname _utsname;
+    if (uname(&_utsname) > -1)
+    {
+        char* isa = _utsname.machine;
+#endif
+        // aarch64 or arm64: arm64
+        if (strcmp("aarch64", isa) == 0 || strcmp("arm64", isa) == 0)
+        {
+            result = ARCH_ARM64;
+        }
+
+        // starts with "armv6" (armv6h or armv6l etc.): armv6
+        else if (strncmp("armv6", isa, strlen("armv6")) == 0)
+        {
+            result = ARCH_ARMV6;
+        }
+
+        // starts with "arm": arm
+        else if (strncmp("arm", isa, strlen("arm")) == 0)
+        {
+            result = ARCH_ARM;
+        }
+
+        // x86_64 or amd64: x64
+        else if (strcmp("x86_64", isa) == 0 || strcmp("amd64", isa) == 0)
+        {
+#ifdef TARGET_OSX
+            int is_translated_process = 0;
+            size_t size = sizeof(is_translated_process);
+            if (sysctlbyname("sysctl.proc_translated", &is_translated_process, &size, NULL, 0) == 0 && is_translated_process == 1)
+                result = ARCH_ARM64;
+            else
+#endif
+            result = ARCH_X64;
+        }
+
+        // ix86 (possible values are i286, i386, i486, i586 and i686): x86
+        else if (strlen(isa) == strlen("i386") && isa[0] == 'i' && isa[2] == '8' && isa[3] == '6')
+        {
+            result = ARCH_X86;
+        }
+
+        else if (strcmp("s390x", isa) == 0)
+        {
+            result = ARCH_S390X;
+        }
+
+        else if (strcmp("loongarch64", isa) == 0)
+        {
+            result = ARCH_LOONGARCH64;
+        }
+    }
+
+    // catch if we have missed a pattern above.
+    assert(result != -1);
+
+    return result;
+#endif
 }

src/native/libs/System.Native/pal_runtimeinformation.h

@@ -11,16 +11,3 @@ PALEXPORT char* SystemNative_GetUnixRelease(void);
 PALEXPORT int32_t SystemNative_GetUnixVersion(char* version, int* capacity);
 
 PALEXPORT int32_t SystemNative_GetOSArchitecture(void);
-
-// Keep in sync with System.Runtime.InteropServices.Architecture enum
-enum 
-{
-    ARCH_X86,
-    ARCH_X64,
-    ARCH_ARM,
-    ARCH_ARM64,
-    ARCH_WASM,
-    ARCH_S390X,
-    ARCH_LOONGARCH64,
-    ARCH_ARMV6,
-};