nrf: Use correct IRAM address for native code execution on nRF52.

On nRF52, the physical SRAM is mapped to 0x20000000 for data access and
0x00800000 for instruction access.  So, while native code is allocated and
written using addresses in the 0x20000000 range, it must execute from the
0x00800000 range.

This commit makes this work correctly on nRF52 MCUs by adjusting the
address.

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

Author: dpgeorge

ports/nrf/main.c

@@ -39,6 +39,7 @@
 #include "py/stackctrl.h"
 #include "py/gc.h"
 #include "py/compile.h"
+#include "py/persistentcode.h"
 #include "extmod/modmachine.h"
 #include "shared/runtime/pyexec.h"
 #include "readline.h"
@@ -369,3 +370,16 @@ void MP_WEAK __assert_func(const char *file, int line, const char *func, const c
     printf("Assertion '%s' failed, at file %s:%d\n", expr, file, line);
     __fatal_error("Assertion failed");
 }
+
+#if MICROPY_EMIT_MACHINE_CODE
+void *nrf_native_code_commit(void *buf, unsigned int len, void *reloc) {
+    (void)len;
+    if (reloc) {
+        // Native code in RAM must execute from the IRAM region at 0x00800000, and so relocations
+        // to text must also point to this region.  The MICROPY_MAKE_POINTER_CALLABLE macro will
+        // adjust the `buf` address from RAM to IRAM.
+        mp_native_relocate(reloc, buf, (uintptr_t)MICROPY_MAKE_POINTER_CALLABLE(buf) & ~1);
+    }
+    return buf;
+}
+#endif

ports/nrf/mpconfigport.h

@@ -320,7 +320,17 @@
 
 // type definitions for the specific machine
 
-#define MICROPY_MAKE_POINTER_CALLABLE(p) ((void *)((mp_uint_t)(p) | 1))
+#if defined(NRF52832) || defined(NRF52840)
+// On nRF52, the physical SRAM is mapped to 0x20000000 for data access and 0x00800000
+// for instruction access.  So convert addresses to make them executable.
+#define MICROPY_PERSISTENT_CODE_TRACK_FUN_DATA (1)
+#define MICROPY_PERSISTENT_CODE_TRACK_BSS_RODATA (0)
+#define MICROPY_MAKE_POINTER_CALLABLE(p) ((void *)(((uintptr_t)(p) - 0x20000000 + 0x00800000) | 1))
+void *nrf_native_code_commit(void *, unsigned int, void *);
+#define MP_PLAT_COMMIT_EXEC(buf, len, reloc) nrf_native_code_commit(buf, len, reloc)
+#else
+#define MICROPY_MAKE_POINTER_CALLABLE(p) ((void *)((uintptr_t)(p) | 1))
+#endif
 
 #define MP_SSIZE_MAX (0x7fffffff)