Implement FFI_EXEC_TRAMPOLINE_TABLE allocator for iOS/ARM.

This provides working closure support on iOS/ARM devices where
PROT_WRITE|PROT_EXEC is not permitted. The code passes basic
smoke tests, but requires further review.

1 files changed, 1 insertions, 79 deletions

diff --git a/src/closures.c b/src/closures.c
index c214196..ac878df 100644
--- a/src/closures.c
+++ b/src/closures.c
@@ -65,85 +65,7 @@
 
 # if FFI_EXEC_TRAMPOLINE_TABLE
 
-// XXX - non-thread-safe, non-portable implementation, intended for initial testing
-#include <mach/mach.h>
-#include <stdio.h>
-#include <stdlib.h>
-
-extern void *ffi_closure_trampoline_table;
-
-static void *tramp_table = NULL;
-static void **config_table = NULL;
-static int tramp_table_free = 0;
-
-void *
-ffi_closure_alloc (size_t size, void **code)
-{
-  if (!code)
-    return NULL;
-
-  /* Allocate our config page and remap the trampoline table */
-  while (tramp_table == NULL) {
-    vm_address_t config_page = 0x0;
-    kern_return_t kt;
-
-    /* Try to allocate two pages */
-    kt = vm_allocate(mach_task_self(), &config_page, PAGE_SIZE*2, VM_FLAGS_ANYWHERE);
-    if (kt != KERN_SUCCESS) {
-      fprintf(stderr, "vm_allocate() failure: %d at %s:%d\n", kt, __FILE__, __LINE__);
-      break;
-    }
-    
-    /* Now drop the second half of the allocation to make room for the trampoline table */
-    kt = vm_deallocate(mach_task_self(), config_page+PAGE_SIZE, PAGE_SIZE);
-    if (kt != KERN_SUCCESS) {
-      fprintf(stderr, "vm_deallocate() failure: %d at %s:%d\n", kt, __FILE__, __LINE__);
-      break;
-    }
-
-    /* Remap the trampoline table to directly follow the config page */
-    vm_address_t table_page = config_page+PAGE_SIZE;
-    vm_prot_t cur_prot;
-    vm_prot_t max_prot;
-
-    kt = vm_remap(mach_task_self(), &table_page, PAGE_SIZE, 0x0, FALSE, mach_task_self(), (vm_address_t) &ffi_closure_trampoline_table, FALSE, &cur_prot, &max_prot, VM_INHERIT_SHARE);
-
-    /* If we lost access to the destination trampoline page, drop our config allocation mapping and retry */
-    if (kt != KERN_SUCCESS) {
-      /* Log unexpected failures */
-      if (kt != KERN_NO_SPACE) {
-        fprintf(stderr, "vm_remap() failure: %d at %s:%d\n", kt, __FILE__, __LINE__);
-      }
-
-      vm_deallocate(mach_task_self(), config_page, PAGE_SIZE);
-      continue;
-    }
-
-    tramp_table = (void *) table_page;
-    config_table = (void **) config_page;
-    config_table += 4; // XXX - there's a 16 byte offset into the config page on ARM
-
-    fprintf(stderr, "[DEBUG] Allocated config page at %p, trampoline page at %p, configs start at %p\n", (void *) config_page, (void *) table_page, config_table);
-  }
-
-  /* Check for permanent allocation failure */
-  if (tramp_table == NULL)
-    return *code = NULL;
-
-  *code = tramp_table + (3 * tramp_table_free);
-  tramp_table_free++;
-
-  void *closure = malloc(size);
-
-  return closure;
-}
-
-void
-ffi_closure_free (void *ptr)
-{
-  // TODO
-  //free (ptr);
-}
+// Per-target implementation; It's unclear what can reasonable be shared between two OS/architecture implementations.
 
 # elif FFI_MMAP_EXEC_WRIT /* !FFI_EXEC_TRAMPOLINE_TABLE */