wasm2c: Segue support for CPUs without wrgsbase instructions

1 files changed, 40 insertions, 24 deletions

diff --git a/test/wasm2c/export-names.txt b/test/wasm2c/export-names.txt
index 7c4e6eda..f5762a19 100644
--- a/test/wasm2c/export-names.txt
+++ b/test/wasm2c/export-names.txt
@@ -123,11 +123,16 @@ void w2c_test_0xE20x9D0xA40xEF0xB80x8F(w2c_test*);
 //     for accessing pointers, and supports memcpy on pointers with custom
 //     "address namespaces". GCC does not support the memcpy requirement, so
 //     this leaves only clang for now.
-// (5) The OS doesn't replace the segment register on context switch which
+// (5) The OS provides a way to query if (rd|wr)gsbase is allowed by the kernel
+// or the implementation has to use a syscall for this.
+// (6) The OS doesn't replace the segment register on context switch which
 //     eliminates windows for now
+//
+// While more OS can be supported in the future, we only support linux for now
 #if WASM_RT_ALLOW_SEGUE && !WABT_BIG_ENDIAN &&                               \
     (defined(__x86_64__) || defined(_M_X64)) && IS_SINGLE_UNSHARED_MEMORY && \
-    __clang__ && __has_builtin(__builtin_ia32_wrgsbase64) && !defined(_WIN32)
+    __clang__ && __has_builtin(__builtin_ia32_wrgsbase64) &&                 \
+    !defined(_WIN32) && defined(__linux__)
 #define WASM_RT_USE_SEGUE 1
 #else
 #define WASM_RT_USE_SEGUE 0
@@ -136,9 +141,20 @@ void w2c_test_0xE20x9D0xA40xEF0xB80x8F(w2c_test*);
 
 #if WASM_RT_USE_SEGUE
 // POSIX uses FS for TLS, GS is free
-#define WASM_RT_SEGUE_READ_BASE() __builtin_ia32_rdgsbase64()
-#define WASM_RT_SEGUE_WRITE_BASE(base) \
-  __builtin_ia32_wrgsbase64((uintptr_t)base)
+static inline void* wasm_rt_segue_read_base() {
+  if (wasm_rt_fsgsbase_inst_supported) {
+    return (void*)__builtin_ia32_rdgsbase64();
+  } else {
+    return wasm_rt_syscall_get_segue_base();
+  }
+}
+static inline void wasm_rt_segue_write_base(void* base) {
+  if (wasm_rt_fsgsbase_inst_supported) {
+    __builtin_ia32_wrgsbase64((uintptr_t)base);
+  } else {
+    wasm_rt_syscall_set_segue_base(base);
+  }
+}
 #define MEM_ADDR_MEMOP(mem, addr, n) ((uint8_t __seg_gs*)(uintptr_t)addr)
 #else
 #define MEM_ADDR_MEMOP(mem, addr, n) MEM_ADDR(mem, addr, n)
@@ -194,7 +210,7 @@ static inline bool func_types_eq(const wasm_rt_func_type_t a,
 #if WASM_RT_USE_SEGUE && WASM_RT_SANITY_CHECKS
 #include <stdio.h>
 #define WASM_RT_CHECK_BASE(mem)                                               \
-  if (((uintptr_t)((mem)->data)) != ((uintptr_t)WASM_RT_SEGUE_READ_BASE())) { \
+  if (((uintptr_t)((mem)->data)) != ((uintptr_t)wasm_rt_segue_read_base())) { \
     puts("Segment register mismatch\n");                                      \
     abort();                                                                  \
   }
@@ -780,60 +796,60 @@ static void init_memories(w2c_test* instance) {
 /* export: '' */
 void w2c_test_(w2c_test* instance) {
 #if WASM_RT_USE_SEGUE
-  uintptr_t segue_saved_base = WASM_RT_SEGUE_READ_BASE();
-  WASM_RT_SEGUE_WRITE_BASE((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
+  void* segue_saved_base = wasm_rt_segue_read_base();
+  wasm_rt_segue_write_base((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
 #endif
   w2c_test__0(instance);
 #if WASM_RT_USE_SEGUE
-  WASM_RT_SEGUE_WRITE_BASE(segue_saved_base);
+  wasm_rt_segue_write_base(segue_saved_base);
 #endif
 }
 
 /* export: '*\2F' */
 void w2c_test_0x2A0x2F(w2c_test* instance) {
 #if WASM_RT_USE_SEGUE
-  uintptr_t segue_saved_base = WASM_RT_SEGUE_READ_BASE();
-  WASM_RT_SEGUE_WRITE_BASE((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
+  void* segue_saved_base = wasm_rt_segue_read_base();
+  wasm_rt_segue_write_base((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
 #endif
   w2c_test__0(instance);
 #if WASM_RT_USE_SEGUE
-  WASM_RT_SEGUE_WRITE_BASE(segue_saved_base);
+  wasm_rt_segue_write_base(segue_saved_base);
 #endif
 }
 
 /* export: '\3F\3F\2F' */
 void w2c_test_0x3F0x3F0x2F(w2c_test* instance) {
 #if WASM_RT_USE_SEGUE
-  uintptr_t segue_saved_base = WASM_RT_SEGUE_READ_BASE();
-  WASM_RT_SEGUE_WRITE_BASE((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
+  void* segue_saved_base = wasm_rt_segue_read_base();
+  wasm_rt_segue_write_base((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
 #endif
   w2c_test__0(instance);
 #if WASM_RT_USE_SEGUE
-  WASM_RT_SEGUE_WRITE_BASE(segue_saved_base);
+  wasm_rt_segue_write_base(segue_saved_base);
 #endif
 }
 
 /* export: '\0A' */
 void w2c_test_0x0A(w2c_test* instance) {
 #if WASM_RT_USE_SEGUE
-  uintptr_t segue_saved_base = WASM_RT_SEGUE_READ_BASE();
-  WASM_RT_SEGUE_WRITE_BASE((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
+  void* segue_saved_base = wasm_rt_segue_read_base();
+  wasm_rt_segue_write_base((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
 #endif
   w2c_test__0(instance);
 #if WASM_RT_USE_SEGUE
-  WASM_RT_SEGUE_WRITE_BASE(segue_saved_base);
+  wasm_rt_segue_write_base(segue_saved_base);
 #endif
 }
 
 /* export: '\E2\9D\A4\EF\B8\8F' */
 void w2c_test_0xE20x9D0xA40xEF0xB80x8F(w2c_test* instance) {
 #if WASM_RT_USE_SEGUE
-  uintptr_t segue_saved_base = WASM_RT_SEGUE_READ_BASE();
-  WASM_RT_SEGUE_WRITE_BASE((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
+  void* segue_saved_base = wasm_rt_segue_read_base();
+  wasm_rt_segue_write_base((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
 #endif
   w2c_test__0(instance);
 #if WASM_RT_USE_SEGUE
-  WASM_RT_SEGUE_WRITE_BASE(segue_saved_base);
+  wasm_rt_segue_write_base(segue_saved_base);
 #endif
 }
 
@@ -850,11 +866,11 @@ void wasm2c_test_instantiate(w2c_test* instance, struct w2c_0x5Cmodule* w2c_0x5C
   init_instance_import(instance, w2c_0x5Cmodule_instance);
   init_memories(instance);
 #if WASM_RT_USE_SEGUE
-  uintptr_t segue_saved_base = WASM_RT_SEGUE_READ_BASE();
-  WASM_RT_SEGUE_WRITE_BASE((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
+  void* segue_saved_base = wasm_rt_segue_read_base();
+  wasm_rt_segue_write_base((*instance->w2c_0x5Cmodule_import0x200x2A0x2F).data);
 #endif
 #if WASM_RT_USE_SEGUE
-  WASM_RT_SEGUE_WRITE_BASE(segue_saved_base);
+  wasm_rt_segue_write_base(segue_saved_base);
 #endif
 }