ports: Refactor os.urandom().

Factor out mp_os_urandom() of each port into extmod/modos.c, which then
calls the port-specific function mp_hal_get_random().

Move mp_hal_get_random() to mphalport where suitable. At the
MIMXRT and SAMD it is left in modos.c, since there are different
implementation depending on the MCU family.

At the ALIF, ESP32, CC3200 and RP2 port the file modos.c was removed,
since it was empty after moving mp_hal_get_random().

Tested for the cc3200, esp32, esp8266, mimxrt, nrf, rp2, samd, stm32
and unix ports. Compiled for the alif and the renesas port.

Signed-off-by: robert-hh <robert@hammelrath.com>

Author: robert-hh

extmod/modos.c

@@ -145,6 +145,18 @@ static mp_obj_t mp_os_dupterm_notify(mp_obj_t obj_in) {
 static MP_DEFINE_CONST_FUN_OBJ_1(mp_os_dupterm_notify_obj, mp_os_dupterm_notify);
 #endif
 
+#if MICROPY_PY_OS_URANDOM
+// This wraps the port-specific mp_hal_get_random(), which is usually defined in mphalport.c.
+static mp_obj_t mp_os_urandom(mp_obj_t num) {
+    mp_int_t n = mp_obj_get_int(num);
+    vstr_t vstr;
+    vstr_init_len(&vstr, n);
+    mp_hal_get_random(n, (uint8_t *)vstr.buf);
+    return mp_obj_new_bytes_from_vstr(&vstr);
+}
+static MP_DEFINE_CONST_FUN_OBJ_1(mp_os_urandom_obj, mp_os_urandom);
+#endif
+
 static const mp_rom_map_elem_t os_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_os) },
 

ports/alif/modos.c

@@ -113,7 +113,6 @@
 
 // Extended modules
 #define MICROPY_EPOCH_IS_1970                   (1)
-#define MICROPY_PY_OS_INCLUDEFILE               "ports/alif/modos.c"
 #define MICROPY_PY_OS_DUPTERM                   (1)
 #define MICROPY_PY_OS_SEP                       (1)
 #define MICROPY_PY_OS_SYNC                      (1)

ports/alif/mpconfigport.h

@@ -269,3 +269,17 @@ void mp_hal_get_mac_ascii(int idx, size_t chr_off, size_t chr_len, char *dest) {
         *dest++ = hexchr[mac[chr_off >> 1] >> (4 * (1 - (chr_off & 1))) & 0xf];
     }
 }
+
+void mp_hal_get_random(size_t n, uint8_t *buf) {
+    uint64_t rnd = 0;
+    size_t rnd_bits = 0;
+    for (int i = 0; i < n; i++) {
+        if (rnd_bits == 0) {
+            rnd = se_services_rand64();
+            rnd_bits = 64;
+        }
+        buf[i] = rnd;
+        rnd >>= 8;
+        rnd_bits -= 8;
+    }
+}

ports/alif/mphalport.c

@@ -375,3 +375,5 @@ void mp_hal_get_mac(int idx, uint8_t buf[6]);
 void mp_hal_get_mac_ascii(int idx, size_t chr_off, size_t chr_len, char *dest);
 
 uint32_t mp_hal_time_get(uint32_t *microseconds);
+
+void mp_hal_get_random(size_t n, uint8_t *buf);

ports/alif/mphalport.h

@@ -49,6 +49,7 @@
 #include "telnet.h"
 #include "pybuart.h"
 #include "utils.h"
+#include "random.h"
 
 #ifdef USE_FREERTOS
 #include "FreeRTOS.h"
@@ -168,6 +169,13 @@ int mp_hal_stdin_rx_chr(void) {
     }
 }
 
+// Fill buf with n random bytes, generated by the hardware random number generator.
+void mp_hal_get_random(size_t n, uint8_t *buf) {
+    for (int i = 0; i < n; i++) {
+        buf[i] = rng_get();
+    }
+}
+
 /******************************************************************************
  DEFINE PRIVATE FUNCTIONS
  ******************************************************************************/

ports/cc3200/hal/cc3200_hal.c

@@ -75,3 +75,5 @@ extern void mp_hal_set_interrupt_char (int c);
 #define mp_hal_delay_us(usec) UtilsDelay(UTILS_DELAY_US_TO_COUNT(usec))
 #define mp_hal_ticks_cpu() (SysTickPeriodGet() - SysTickValueGet())
 #define mp_hal_time_ns() (0) // not implemented
+
+void mp_hal_get_random(size_t n, uint8_t *buf);

ports/cc3200/hal/cc3200_hal.h

@@ -95,7 +95,6 @@
 #define MICROPY_PY_JSON                             (1)
 #define MICROPY_PY_RE                               (1)
 #define MICROPY_PY_OS                               (1)
-#define MICROPY_PY_OS_INCLUDEFILE                   "ports/cc3200/mods/modos.c"
 #define MICROPY_PY_OS_DUPTERM                       (1)
 #define MICROPY_PY_OS_SYNC                          (1)
 #define MICROPY_PY_OS_URANDOM                       (1)