fix JuliaLang#11646 on OS X

rather than checking if the memory is "in core" (loaded in physical memory), use msync to determine if the page address was valid/mapped for our process

src/gc.c

@@ -66,8 +66,6 @@ static GC_Num gc_num = {0,0,0,0,0,0,0,0,0,0,0,0};
 #define total_allocd_bytes gc_num.total_allocd
 #define allocd_bytes_since_sweep gc_num.since_sweep
 
-static long system_page_size;
-
 // malloc wrappers, aligned allocation
 
 #if defined(_P64) || defined(__APPLE__)
@@ -672,7 +670,7 @@ static NOINLINE void *malloc_page(void)
 #ifdef _OS_WINDOWS_
  char* mem = (char*)VirtualAlloc(NULL, sizeof(region_t) + GC_PAGE_SZ, MEM_RESERVE, PAGE_READWRITE);
 #else
- if (GC_PAGE_SZ > system_page_size)
+ if (GC_PAGE_SZ > jl_page_size)
  alloc_size += GC_PAGE_SZ;
  char* mem = (char*)mmap(0, alloc_size, PROT_READ | PROT_WRITE, MAP_NORESERVE | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  mem = mem == MAP_FAILED ? NULL : mem;
@@ -681,7 +679,7 @@ static NOINLINE void *malloc_page(void)
  jl_printf(JL_STDERR, "could not allocate pools\n");
  abort();
  }
- if (GC_PAGE_SZ > system_page_size) {
+ if (GC_PAGE_SZ > jl_page_size) {
  // round data pointer up to the nearest GC_PAGE_DATA-aligned boundary
  // if mmap didn't already do so
  alloc_size += GC_PAGE_SZ;
@@ -751,11 +749,11 @@ static void free_page(void *p)
  free(region->meta[pg_idx].ages);
  // tell the OS we don't need these pages right now
  size_t decommit_size = GC_PAGE_SZ;
- if (GC_PAGE_SZ < system_page_size) {
+ if (GC_PAGE_SZ < jl_page_size) {
  // ensure so we don't release more memory than intended
- size_t n_pages = (GC_PAGE_SZ + system_page_size - 1) / GC_PAGE_SZ;
- decommit_size = system_page_size;
- p = (void*)((uintptr_t)&region->pages[pg_idx][0] & ~(system_page_size - 1)); // round down to the nearest page
+ size_t n_pages = (GC_PAGE_SZ + jl_page_size - 1) / GC_PAGE_SZ;
+ decommit_size = jl_page_size;
+ p = (void*)((uintptr_t)&region->pages[pg_idx][0] & ~(jl_page_size - 1)); // round down to the nearest page
  pg_idx = PAGE_INDEX(region, (char*)p+GC_PAGE_OFFSET);
  if (pg_idx + n_pages > REGION_PG_COUNT) goto no_decommit;
  for (; n_pages--; pg_idx++) {
@@ -2546,7 +2544,6 @@ static void jl_mk_thread_heap(void) {
 // System-wide initializations
 void jl_gc_init(void)
 {
- system_page_size = jl_getpagesize();
  jl_mk_thread_heap();
 
  arraylist_new(&finalizer_list, 0);

src/init.c

@@ -291,7 +291,7 @@ void segv_handler(int sig, siginfo_t *info, void *context)
  jl_throw(jl_memory_exception);
  }
 #ifdef SEGV_EXCEPTION
- else {
+ else if (sig == SIGSEGV) {
  sigemptyset(&sset);
  sigaddset(&sset, SIGSEGV);
  sigprocmask(SIG_UNBLOCK, &sset, NULL);
@@ -757,14 +757,12 @@ void *mach_segv_listener(void *arg)
 }
 
 #ifdef SEGV_EXCEPTION
-
 void darwin_segv_handler(unw_context_t *uc)
 {
  bt_size = rec_backtrace_ctx(bt_data, MAX_BT_SIZE, uc);
  jl_exception_in_transit = jl_segv_exception;
  jl_rethrow();
 }
-
 #endif
 
 void darwin_stack_overflow_handler(unw_context_t *uc)
@@ -822,8 +820,7 @@ kern_return_t catch_exception_raise(mach_port_t exception_port,
 #ifdef SEGV_EXCEPTION
  if (1) {
 #else
- if (is_addr_on_stack((void*)fault_addr) ||
- ((exc_state.__err & PAGE_PRESENT) == PAGE_PRESENT)) {
+ if (msync((void*)(fault_addr & ~(jl_page_size - 1)), 1, MS_ASYNC) == 0) { // check if this was a valid address
 #endif
  ret = thread_get_state(thread,x86_THREAD_STATE64,(thread_state_t)&state,&count);
  HANDLE_MACH_ERROR("thread_get_state(2)",ret);
@@ -845,14 +842,14 @@ kern_return_t catch_exception_raise(mach_port_t exception_port,
  memset(uc,0,sizeof(unw_context_t));
  memcpy(uc,&old_state,sizeof(x86_thread_state64_t));
  state.__rdi = (uint64_t)uc;
- if ((exc_state.__err & PAGE_PRESENT) == PAGE_PRESENT)
- state.__rip = (uint64_t)darwin_accerr_handler;
+ if (is_addr_on_stack((void*)fault_addr))
+ state.__rip = (uint64_t)darwin_stack_overflow_handler;
 #ifdef SEGV_EXCEPTION
- else if (!is_addr_on_stack((void*)fault_addr))
+ else if (msync((void*)(fault_addr & ~(jl_page_size - 1)), 1, MS_ASYNC) != 0)
  state.__rip = (uint64_t)darwin_segv_handler;
 #endif
  else
- state.__rip = (uint64_t)darwin_stack_overflow_handler;
+ state.__rip = (uint64_t)darwin_accerr_handler;
 
  state.__rbp = state.__rsp;
  ret = thread_set_state(thread,x86_THREAD_STATE64,(thread_state_t)&state,count);
@@ -987,6 +984,7 @@ static void jl_resolve_sysimg_location(JL_IMAGE_SEARCH rel)
 void attach_exception_port()
 {
  kern_return_t ret;
+ // http:https://www.opensource.apple.com/source/xnu/xnu-2782.1.97/osfmk/man/thread_set_exception_ports.html
  ret = thread_set_exception_ports(mach_thread_self(),EXC_MASK_BAD_ACCESS,segv_port,EXCEPTION_DEFAULT,MACHINE_THREAD_STATE);
  HANDLE_MACH_ERROR("thread_set_exception_ports",ret);
 }