Improve dlopen() on Apple Silicon

- Introduce MAP_JIT which is zero on other platforms
- Invent __jit_begin() and __jit_end() which wrap Apple's APIs
- Runtime dispatch to sys_icache_invalidate() in __clear_cache()

libc/runtime/jit.c

@@ -0,0 +1,37 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2023 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/dce.h"
+#include "libc/runtime/runtime.h"
+#include "libc/runtime/syslib.internal.h"
+
+void __jit_begin(void) {
+  if (IsXnuSilicon()) {
+    if (__syslib->__pthread_jit_write_protect_supported_np()) {
+      __syslib->__pthread_jit_write_protect_np(false);
+    }
+  }
+}
+
+void __jit_end(void) {
+  if (IsXnuSilicon()) {
+    if (__syslib->__pthread_jit_write_protect_supported_np()) {
+      __syslib->__pthread_jit_write_protect_np(true);
+    }
+  }
+}

libc/runtime/runtime.h

@@ -115,6 +115,8 @@ bool32 _isheap(void *);
 /* code morphing */
 void __morph_begin(void);
 void __morph_end(void);
+void __jit_begin(void);
+void __jit_end(void);
 void __clear_cache(void *, void *);
 /* portability */
 int NtGetVersion(void) pureconst;

libc/runtime/runtime.mk

@@ -45,6 +45,7 @@ LIBC_RUNTIME_A_DIRECTDEPS =				\
 	LIBC_STR					\
 	LIBC_SYSV					\
 	LIBC_SYSV_CALLS					\
+	THIRD_PARTY_COMPILER_RT				\
 	THIRD_PARTY_NSYNC				\
 	THIRD_PARTY_PUFF				\
 	THIRD_PARTY_XED

libc/runtime/syslib.internal.h

@@ -12,7 +12,7 @@ COSMOPOLITAN_C_START_
  */
 
 #define SYSLIB_MAGIC   ('s' | 'l' << 8 | 'i' << 16 | 'b' << 24)
-#define SYSLIB_VERSION 6
+#define SYSLIB_VERSION 8
 
 typedef uint64_t dispatch_time_t;
 typedef uint64_t dispatch_semaphore_t;