unix/alloc: Don't trace executable memory for GC pointers.

This tracing was originally needed for three reasons:

1. To trace object/raw-code pointers embedded in native code, eg from
   @micropython.native functions.

2. To trace pointers to BSS/rodata from relocated viper code.

3. For libffi tracing.

The tracing in point 1 was made unnecessary long ago in commit
7d4b6cc868 (see also commit
bbccb0f630 which removed scanning of native
code on the esp8266 port).

Since the previous commit, point 2 is no longer needed.

For point 3, this was made unnecessary in the recent commit
9796625457.

Signed-off-by: Damien George <damien@micropython.org>

ports/unix/alloc.c

@@ -31,7 +31,6 @@
 #include <sys/mman.h>
 
 #include "py/mpstate.h"
-#include "py/gc.h"
 
 #if MICROPY_EMIT_NATIVE || (MICROPY_PY_FFI && MICROPY_FORCE_PLAT_ALLOC_EXEC)
 
@@ -79,12 +78,6 @@ void mp_unix_free_exec(void *ptr, size_t size) {
     }
 }
 
-void mp_unix_mark_exec(void) {
-    for (mmap_region_t *rg = MP_STATE_VM(mmap_region_head); rg != NULL; rg = rg->next) {
-        gc_collect_root(rg->ptr, rg->len / sizeof(mp_uint_t));
-    }
-}
-
 MP_REGISTER_ROOT_POINTER(void *mmap_region_head);
 
 #endif // MICROPY_EMIT_NATIVE || (MICROPY_PY_FFI && MICROPY_FORCE_PLAT_ALLOC_EXEC)

ports/unix/gccollect.c

@@ -39,9 +39,6 @@ void gc_collect(void) {
     #if MICROPY_PY_THREAD
     mp_thread_gc_others();
     #endif
-    #if MICROPY_EMIT_NATIVE
-    mp_unix_mark_exec();
-    #endif
     gc_collect_end();
 }
 

ports/unix/mpconfigport.h

@@ -168,7 +168,6 @@ extern const struct _mp_print_t mp_stderr_print;
 // For the native emitter configure how to mark a region as executable.
 void mp_unix_alloc_exec(size_t min_size, void **ptr, size_t *size);
 void mp_unix_free_exec(void *ptr, size_t size);
-void mp_unix_mark_exec(void);
 #define MP_PLAT_ALLOC_EXEC(min_size, ptr, size) mp_unix_alloc_exec(min_size, ptr, size)
 #define MP_PLAT_FREE_EXEC(ptr, size) mp_unix_free_exec(ptr, size)
 #ifndef MICROPY_FORCE_PLAT_ALLOC_EXEC