Add rand() syscall

kernel/syscall/randcrypto.c

@@ -0,0 +1,8 @@
+#include <stdint.h>
+#include <stddef.h>
+#include "hal/hal.h"
+#include "syscall.h"
+
+int32_t SYSCALL0(sys_rand) {
+  return hal_randnum();
+}

kernel/syscall/randcrypto.h

@@ -0,0 +1,8 @@
+#ifndef SYSCALL_RANDCRYPTO_H_
+#define SYSCALL_RANDCRYPTO_H_
+
+#include "syscall.h"
+
+int32_t SYSCALL0(sys_rand);
+
+#endif // SYSCALL_RANDCRYPTO_H_

kernel/syscall/syscall.c

@@ -9,6 +9,7 @@
 #include "mman.h"
 #include "sched.h"
 #include "devctl.h"
+#include "randcrypto.h"
 
 int32_t SYSCALL1(sys_debugprint, string) {
   char *p = (char *)string;
@@ -25,4 +26,5 @@ SyscallFn SYSCALL_TABLE[SYSCALLS_MAX] = {
   [SYS_MMAN_UNMAP] = &sys_mman_unmap,
   [SYS_SCHEDRELEASE] = &sys_schedrelease,
   [SYS_DEVCTL]     = &sys_devctl,
+  [SYS_RAND]       = &sys_rand,
 };