Initial Windows on ARM (AArch64) Support (#249)

* Conditionally include ntdll.dll

* Use text relocation instead of GOT

* Use FlushInstructionCache instead of clear_cache for arm64

* Load address in two stages (adrp, add)

* objc_msgSend.aarch64.S add comments

* Add seh directives

* Move .seh_proc into slow sloop section

* Comment out cfi directives

* Substitute raw .seh directives with macros

* Add documentation of SEH annotations

* Detect CPU Architecture with preprocessor

* Cleanup CMakeLists.txt

Co-authored-by: David Chisnall <davidchisnall@users.noreply.github.com>

* Remove line in objc_msgSend.aarch64.S

Co-authored-by: David Chisnall <davidchisnall@users.noreply.github.com>

* Change Test CMakeList to use ARCHITECTURE var

* Use existing clear cache macro

* Change _WIN64 to _WIN32 and reorder labels

* Remove macro and replace _WIN64 with _WIN32

* Remove argument from non-win32 macro

---------

Co-authored-by: David Chisnall <davidchisnall@users.noreply.github.com>

CMake/detect_arch.c

@@ -0,0 +1,12 @@
+// detect_arch.c
+#if defined(__aarch64__)
+#error aarch64
+#elif defined(__arm__)
+#error arm
+#elif defined(__i386__)
+#error i386
+#elif defined(__x86_64__)
+#error x86_64
+#else
+#error unknown
+#endif

CMakeLists.txt

@@ -34,6 +34,21 @@ if (MSVC)
 	set(objc_LINK_FLAGS "/DEBUG /INCREMENTAL:NO ${objc_LINK_FLAGS}")
 endif()
 
+# Get Architecture without relying on CMake
+try_compile(
+    COMPILE_SUCCESS
+    ${CMAKE_BINARY_DIR}
+    ${CMAKE_SOURCE_DIR}/CMake/detect_arch.c
+    OUTPUT_VARIABLE COMPILE_OUTPUT
+)
+
+if(NOT COMPILE_SUCCESS)
+    string(REGEX MATCH "(aarch64|arm|i386|x86_64|unknown)" ARCHITECTURE ${COMPILE_OUTPUT})
+endif()
+
+set(ARCHITECTURE ${ARCHITECTURE} CACHE STRING "Architecture Type")
+message(STATUS "Architecture: ${ARCHITECTURE}")
+
 # Build configuration
 add_compile_definitions(GNUSTEP __OBJC_RUNTIME_INTERNAL__=1)
 
@@ -215,6 +230,10 @@ target_sources(objc PRIVATE ${libobjc_CXX_SRCS})
 
 include(FindThreads)
 target_link_libraries(objc Threads::Threads)
+# Link against ntdll.dll for RtlRaiseException
+if (WIN32)
+	target_link_libraries(objc ntdll.dll)
+endif()
 
 
 set_target_properties(objc PROPERTIES
@@ -342,8 +361,6 @@ configure_file(
 add_custom_target(uninstall
 	COMMAND ${CMAKE_COMMAND} -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake)
 
-
-
 if (TESTS)
 	enable_testing()
 	add_subdirectory(Test)

Test/CMakeLists.txt

@@ -80,7 +80,7 @@ if (ENABLE_ALL_OBJC_ARC_TESTS)
 endif()
 
 # UnexpectedException test currently fails on ARM and needs to be fixed
-if (NOT CMAKE_SYSTEM_PROCESSOR MATCHES "^(arm|aarch64)")
+if(NOT ARCHITECTURE MATCHES "^(arm|aarch64)")
     list(APPEND TESTS UnexpectedException.m)
 endif()
 

block_to_imp.c

@@ -12,6 +12,8 @@
 #include <unistd.h>
 #include <sys/types.h>
 #include <sys/mman.h>
+#else
+#include "safewindows.h"
 #endif
 #include "objc/runtime.h"
 #include "objc/blocks_runtime.h"
@@ -22,7 +24,13 @@
 #ifndef __has_builtin
 #define __has_builtin(x) 0
 #endif
-#if __has_builtin(__builtin___clear_cache)
+
+#if defined(_WIN32) && (defined(__arm__) || defined(__aarch64__))
+    static inline void __clear_cache(void* start, void* end) {
+        FlushInstructionCache(GetCurrentProcess(), start, end - start);
+    }
+    #define clear_cache __clear_cache
+#elif __has_builtin(__builtin___clear_cache)
     #define clear_cache __builtin___clear_cache
 #else
     void __clear_cache(void* start, void* end);
@@ -36,7 +44,6 @@ void __clear_cache(void* start, void* end);
 #endif
 
 #ifdef _WIN32
-#include "safewindows.h"
 #if defined(WINAPI_FAMILY) && WINAPI_FAMILY != WINAPI_FAMILY_DESKTOP_APP && _WIN32_WINNT >= 0x0A00
 // Prefer the *FromApp versions when we're being built in a Windows Store App context on
 // Windows >= 10. *FromApp require the application to be manifested for "codeGeneration".
@@ -178,6 +185,7 @@ static struct trampoline_set *alloc_trampolines(char *start, char *end)
 	metadata->buffers->headers[HEADERS_PER_PAGE-1].block = NULL;
 	mprotect(metadata->buffers->rx_buffer, PAGE_SIZE, PROT_READ | PROT_EXEC);
 	clear_cache(metadata->buffers->rx_buffer, &metadata->buffers->rx_buffer[PAGE_SIZE]);
+
 	return metadata;
 }
 

objc_msgSend.aarch64.S

@@ -1,15 +1,88 @@
 #define ARGUMENT_SPILL_SIZE (8*10 + 8*16)
-.macro MSGSEND receiver, sel
+
-	.cfi_startproc
+/* Windows ARM64 Exception Handling
-	cbz    \receiver, 4f                   // Skip everything if the receiver is nil
+ *
+ * Structured Exception Handling (SEH) on Windows ARM64 differs from the x64
+ * implementation. Functions consist of a single prologue and zero or more
+ * epilogues. Instead of using offsets for the .seh* directives to manipulate the
+ * stack frame, each directive corresponds to a single instruction.
+ *
+ * This presents a challenge for our objc_msgSend function, which only modifies
+ * the stack when a slow lookup is needed (see label "5").
+ *
+ * To address this, we move the directive marking the start of a function deep
+ * into the msgSend body to prevent marking every instruction as ".seh_nop."
+ *
+ *   For Windows:
+ *  - EH_START(x): Start of function (no effect on Windows)
+ *  - EH_END(x): End of function (no effect on Windows)
+ *  - EH_START_AT_OFFSET(x): Mark Start of function (Delayed)
+ *  - EH_END_AT_OFFSET(x): Mark End of function (Delayed)
+ *  - EH_END_PROLOGUE: End of function prologue
+ *  - EH_START_EPILOGUE: Start of function epilogue
+ *  - EH_END_EPILOGUE: End of function epilogue
+ *  - EH_SAVE_FP_LR(x): Save Frame Pointer and Link Register
+ *  - EH_STACK_ALLOC(x): Stack allocation (inside prologue)
+ *  - EH_ADD_FP(x): Add to Frame Pointer
+ *  - EH_NOP: Mark instruction with no unwinding relevance
+ *
+ * For non-64-bit Windows systems or other platforms, these macros have no effect and can be used without causing issues.
+ */
+
+#ifdef _WIN32
+#   define EH_START
+#   define EH_END
+
+#   define EH_START_AT_OFFSET .seh_proc objc_msgSend
+#   define EH_END_AT_OFFSET .seh_endproc objc_msgSend
+
+#   define EH_END_PROLOGUE .seh_endprologue
+#   define EH_START_EPILOGUE .seh_startepilogue
+#   define EH_END_EPILOGUE .seh_endepilogue
+
+#   define EH_SAVE_FP_LR(x) .seh_save_fplr x
+#   define EH_STACK_ALLOC(x) .seh_stackalloc x
+#   define EH_ADD_FP(x) .seh_add_fp	x
+
+#   define EH_NOP .seh_nop
+#else
+// Marks the real start and end of the function
+#   define EH_START .cfi_startproc
+#   define EH_END .cfi_endproc
+
+// The following directives are either not
+// needed or not available with CFI
+#   define EH_START_AT_OFFSET
+#   define EH_END_AT_OFFSET
+#   define EH_END_PROLOGUE
+#   define EH_START_EPILOGUE
+#   define EH_END_EPILOGUE
+#   define EH_SAVE_FP_LR(x)
+#   define EH_STACK_ALLOC(x)
+#   define EH_ADD_FP(x)
+#   define EH_NOP
+#endif
+
+.globl CDECL(objc_msgSend_fpret)
+TYPE_DIRECTIVE(CDECL(objc_msgSend_fpret), %function)
+.globl CDECL(objc_msgSend)
+TYPE_DIRECTIVE(CDECL(objc_msgSend), %function)
+.globl CDECL(objc_msgSend_stret)
+TYPE_DIRECTIVE(CDECL(objc_msgSend_stret), %function)
+CDECL(objc_msgSend):
+CDECL(objc_msgSend_fpret):
+CDECL(objc_msgSend_stret):
+	EH_START
+
+	cbz    x0, 4f                   // Skip everything if the receiver is nil
 	                                       // Jump to 6: if this is a small object
-	ubfx    x9, \receiver, #0, #SMALLOBJ_BITS
+	ubfx    x9, x0, #0, #SMALLOBJ_BITS
 	cbnz   x9, 6f
 
-	ldr    x9, [\receiver]                 // Load class to x9 if not a small int
+	ldr    x9, [x0]                 // Load class to x9 if not a small int
 1:
 	ldr    x9, [x9, #DTABLE_OFFSET]        // Dtable -> x9
-	ldr    w10, [\sel]                     // selector->index -> x10
+	ldr    w10, [x1]                     // selector->index -> x10
 	ldr    w11, [x9, #SHIFT_OFFSET]        // dtable->shift -> x11
 	
 	cmp    x11, #8                         // If this is a small dtable, jump to the
@@ -41,59 +114,114 @@
 	mov    v0.d[1], x0
 	br     lr
 5:                                        // Slow lookup
+	EH_START_AT_OFFSET
+
 	                                      // Save anything that will be clobbered by
-	                                      // the call
+	                                      // the call.
+										  // Note that we pre-index (see "!"), meaning
+										  // that we adjust the sp before storing the pair
+										  // of registers.
 	stp    x0, x1, [sp, #-(ARGUMENT_SPILL_SIZE)]!
-	stp    x2, x3, [sp, #16]              // The order is arbitrary, except that
+	EH_STACK_ALLOC((ARGUMENT_SPILL_SIZE))
-	stp    x4, x5, [sp, #32]              // fp and lr must be spilled together and
+
-	stp    x6, x7, [sp, #48]              // it's convenient if \receiver is spilled at sp
+	stp    x2, x3, [sp, #16]
+	EH_NOP                                // The following instructions can be ignored by SEH
+	stp    x4, x5, [sp, #32]
+	EH_NOP
+	stp    x6, x7, [sp, #48]
+	EH_NOP
 	stp    q0, q1, [sp, #64]
+	EH_NOP
 	stp    q2, q3, [sp, #96]
+	EH_NOP
 	stp    q4, q5, [sp, #128]
+	EH_NOP
 	stp    q6, q7, [sp, #160]
-	stp    fp, lr, [sp, #192]
+	EH_NOP
-	add    fp, sp, 192
+	stp    fp, lr, [sp, #192]             // The order is arbitrary, except that
-	stp    \receiver, x8, [sp, #-16]!
+	EH_SAVE_FP_LR(192)                    // fp and lr must be spilled together
+
+	add    fp, sp, 192					  // Adjust frame pointer
+	EH_ADD_FP(192)
+	stp    x0, x8, [sp, #-16]!     // it's convenient if x0 is spilled at sp
+	EH_STACK_ALLOC(16)					  // stp performed pre-indexing by sp-16
+
+	EH_END_PROLOGUE
+
+	#ifndef _WIN32
 	.cfi_def_cfa fp, 16
 	.cfi_offset fp, -16
 	.cfi_offset lr, -8
+	#endif
 	                                      // We now have all argument registers, the link
 	                                      // register and the receiver spilled on the
 	                                      // stack, with sp containing
 	                                      // the address of the receiver
 
 	mov    x0, sp                         // &self, _cmd in arguments
-	mov    x1, \sel
+	mov    x1, x1
-	bl     CDECL(slowMsgLookup)           // This is the only place where the CFI directives
+	bl     CDECL(slowMsgLookup)           // This is the only place where the EH directives
 	                                      // have to be accurate...
 	mov    x9, x0                         // IMP -> x9
+
+	EH_START_EPILOGUE
 	ldp    x0, x1, [sp, #16]              // Reload spilled argument registers
+	EH_NOP
 	ldp    x2, x3, [sp, #32]
+	EH_NOP
 	ldp    x4, x5, [sp, #64]
+	EH_NOP
 	ldp    x6, x7, [sp, #64]
+	EH_NOP
 	ldp    q0, q1, [sp, #80]
+	EH_NOP
 	ldp    q2, q3, [sp, #112]
+	EH_NOP
 	ldp    q4, q5, [sp, #144]
+	EH_NOP
 	ldp    q6, q7, [sp, #176]
+	EH_NOP
 	ldp    fp, lr, [sp, #208]
-	ldp    \receiver, x8, [sp], #(ARGUMENT_SPILL_SIZE + 16)
+	EH_SAVE_FP_LR(208)
+
+										  // Post-increment sp += ARGUMENT_SPILL_SIZE +16
+	ldp    x0, x8, [sp], #(ARGUMENT_SPILL_SIZE + 16)
+	EH_STACK_ALLOC((ARGUMENT_SPILL_SIZE + 16))
+
+	EH_END_EPILOGUE
+	EH_END_AT_OFFSET
+
 	br     x9
 6:
-	adrp   x10, :got:SmallObjectClasses
+										  // Load 63:12 of SmallObjectClasses address
-	ldr    x10, [x10, :got_lo12:SmallObjectClasses]
+										  // We use the CDECL macro as Windows prefixes
+										  // cdecl conforming symbols with "_".
+	adrp   x10, CDECL(SmallObjectClasses) // The macro handles this transparently.
+
+										  // Add lower 12-bits of SmallObjectClasses address to x10
+	add    x10, x10, :lo12:CDECL(SmallObjectClasses)
 	ldr    x9, [x10, x9, lsl #3]
+
 	b      1b
-	.cfi_endproc
+	EH_END
-.endm
 
-.globl CDECL(objc_msgSend_fpret)
+#ifdef _WIN32
-TYPE_DIRECTIVE(CDECL(objc_msgSend_fpret), %function)
+.text
-.globl CDECL(objc_msgSend)
+.def objc_msgSend;
-TYPE_DIRECTIVE(CDECL(objc_msgSend), %function)
+.scl 2;
-.globl CDECL(objc_msgSend_stret)
+.type 32;
-TYPE_DIRECTIVE(CDECL(objc_msgSend_stret), %function)
+.endef
-CDECL(objc_msgSend):
+.def objc_msgSend_fpret;
-CDECL(objc_msgSend_fpret):
+.scl 2;
-CDECL(objc_msgSend_stret):
+.type 32;
-	MSGSEND x0, x1
+.endef
+.def objc_msgSend_stret;
+.scl 2;
+.type 32;
+.endef
 
+.section        .drectve,"yn"
+.ascii  " /EXPORT:objc_msgSend"
+.ascii  " /EXPORT:objc_msgSend_fpret"
+.ascii  " /EXPORT:objc_msgSend_stret"
+#endif