build: add macOS (Apple Silicon) build support

macOS compiles the existing POSIX/Linux code paths (KYTY_PLATFORM_LINUX)
targeting x86_64 under Rosetta 2. Adds an APPLE branch to the build:
selects Apple's ld64 linker, unsets the Ninja response-file forcing (Apple
ar has no @file support), derives the target arch from CMAKE_OSX_ARCHITECTURES
for cpuinfo/ffmpeg, and re-signs the binary post-build with JIT entitlements
(required to execute written trampolines and Rosetta-translated guest code).

All changes are guarded by if(APPLE); Windows and Linux configuration is
unchanged.

3rdparty/CMakeLists.txt

@@ -44,7 +44,17 @@ set(SPDLOG_NO_EXCEPTIONS ON CACHE BOOL "" FORCE)
 add_subdirectory(spdlog EXCLUDE_FROM_ALL)
 
 if (NOT TARGET FFmpeg::ffmpeg)
-	if(CMAKE_SYSTEM_PROCESSOR MATCHES "^(aarch64|arm64|ARM64)$")
+	# On macOS the target arch is driven by CMAKE_OSX_ARCHITECTURES, not the host
+	# CMAKE_SYSTEM_PROCESSOR (which reports arm64 even for an x86_64/Rosetta build).
+	if(APPLE AND CMAKE_OSX_ARCHITECTURES)
+		if(CMAKE_OSX_ARCHITECTURES MATCHES "^(x86_64)$")
+			set(ARCHITECTURE x86_64)
+		elseif(CMAKE_OSX_ARCHITECTURES MATCHES "^(arm64)$")
+			set(ARCHITECTURE arm64)
+		else()
+			set(ARCHITECTURE x86_64 arm64) # universal
+		endif()
+	elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(aarch64|arm64|ARM64)$")
 		set(ARCHITECTURE arm64)
 	else()
 		set(ARCHITECTURE x86_64)

3rdparty/cpuinfo/CMakeLists.txt

@@ -5,7 +5,14 @@ set(cpuinfo_src
 	deps/clog/src/clog.c
 )
 
-if(CMAKE_SYSTEM_PROCESSOR MATCHES "^(i[3-6]86|AMD64|x86(_64)?)$")
+# On Apple the target arch is driven by CMAKE_OSX_ARCHITECTURES, not the host
+# CMAKE_SYSTEM_PROCESSOR (which is arm64 even for an x86_64/Rosetta build).
+set(CPUINFO_TARGET_PROC "${CMAKE_SYSTEM_PROCESSOR}")
+if(APPLE AND CMAKE_OSX_ARCHITECTURES)
+	list(GET CMAKE_OSX_ARCHITECTURES 0 CPUINFO_TARGET_PROC)
+endif()
+
+if(CPUINFO_TARGET_PROC MATCHES "^(i[3-6]86|AMD64|x86(_64)?)$")
 	list(APPEND cpuinfo_src
 		src/x86/init.c
 		src/x86/info.c
@@ -19,11 +26,13 @@ if(CMAKE_SYSTEM_PROCESSOR MATCHES "^(i[3-6]86|AMD64|x86(_64)?)$")
 		src/x86/cache/deterministic.c)
 	if(LINUX OR ANDROID)
 		list(APPEND cpuinfo_src src/x86/linux/init.c src/x86/linux/cpuinfo.c)
+	elseif(APPLE)
+		list(APPEND cpuinfo_src src/x86/mach/init.c src/mach/topology.c)
 	else()
 		list(APPEND cpuinfo_src src/x86/windows/init.c)
 	endif()
-	
-elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(armv[5-8].*|aarch64|arm64)$")
+
+elseif(CPUINFO_TARGET_PROC MATCHES "^(armv[5-8].*|aarch64|arm64)$")
 	list(APPEND cpuinfo_src src/arm/uarch.c src/arm/cache.c)
 	
 	if(LINUX OR ANDROID)

src/CMakeLists.txt

@@ -10,8 +10,8 @@ if(CMAKE_SYSTEM_NAME MATCHES ".*Linux")
 	set(LINUX TRUE)
 endif()
 
-if (NOT (WIN32 OR LINUX))
-    message(FATAL_ERROR "only Windows and Linux builds are supported")
+if (NOT (WIN32 OR LINUX OR APPLE))
+    message(FATAL_ERROR "only Windows, Linux, and macOS builds are supported")
 endif()
 
 set(CMAKE_CXX_STANDARD 20)
@@ -43,8 +43,9 @@ else()
 	set(KYTY_BUILD KYTY_BUILD_RELEASE)
 endif()
 
-if(LINUX)
-	set(KYTY_PLATFORM KYTY_PLATFORM_LINUX)	
+if(LINUX OR APPLE)
+	# macOS rides the POSIX/Linux code paths until it gets a dedicated platform
+	set(KYTY_PLATFORM KYTY_PLATFORM_LINUX)
 else()
 	set(KYTY_PLATFORM KYTY_PLATFORM_WINDOWS)
 endif()
@@ -61,6 +62,8 @@ if(CMAKE_CXX_COMPILER_ID MATCHES "^(Apple)?Clang$")
 	if(WIN32 AND KYTY_CXX_COMPILER_NAME STREQUAL "clang-cl")
 		set(KYTY_CLANG_CL TRUE)
 		set(KYTY_LINKER LLD_LINK)
+	elseif(APPLE)
+		set(KYTY_LINKER LD64) # Apple's default linker; lld flags don't apply
 	else()
 		set(KYTY_LINKER LLD)
 	endif()
@@ -331,6 +334,18 @@ endif()
 
 add_dependencies(kyty_emulator KytyGitVersion)
 
+if(APPLE)
+	# The emulator writes x86-64 trampolines/PLT stubs into memory and executes them, and
+	# runs guest code under Rosetta. That requires the JIT / unsigned-executable-memory
+	# entitlements, so re-sign the binary after every link (an unsigned/relinked binary
+	# reverts to the hardened defaults and aborts when it first executes written code).
+	add_custom_command(TARGET kyty_emulator POST_BUILD
+		COMMAND codesign -s - --force --options runtime
+			--entitlements "${CMAKE_CURRENT_SOURCE_DIR}/macos_jit.entitlements"
+			$<TARGET_FILE:kyty_emulator>
+		COMMENT "Codesign kyty_emulator with JIT entitlements (macOS)")
+endif()
+
 install(TARGETS kyty_emulator DESTINATION .)
 if(KYTY_BUILD_LAUNCHER)
 	add_subdirectory(launcher)

src/macos_jit.entitlements

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+    <key>com.apple.security.cs.allow-jit</key>
+    <true/>
+    <key>com.apple.security.cs.allow-unsigned-executable-memory</key>
+    <true/>
+    <key>com.apple.security.cs.disable-executable-page-protection</key>
+    <true/>
+    <key>com.apple.security.cs.disable-library-validation</key>
+    <true/>
+</dict>
+</plist>

src/utils.cmake

@@ -68,7 +68,15 @@ set(KYTY_WARNINGS_ARE_ERRORS OFF)
 set(KYTY_C_FLAGS "")
 set(KYTY_CPP_FLAGS "")
 
-SET(CMAKE_NINJA_FORCE_RESPONSE_FILE 1 CACHE INTERNAL "")
+# Apple's /usr/bin/ar does not understand @response-file syntax, and macOS has a
+# large ARG_MAX so response files aren't needed. Note: the Ninja generator forces a
+# response file whenever CMAKE_NINJA_FORCE_RESPONSE_FILE is *defined* (it tests
+# definedness, not the value), so on Apple it must be fully unset, not set to 0.
+if(APPLE)
+	unset(CMAKE_NINJA_FORCE_RESPONSE_FILE CACHE)
+else()
+	SET(CMAKE_NINJA_FORCE_RESPONSE_FILE 1 CACHE INTERNAL "")
+endif()
 
 if(KYTY_CLANG_CL)
 	if(CMAKE_CXX_FLAGS MATCHES "/W[0-4]")