Implement zephyr urandom and monotime (#19142)

* implement urandom for Zephyr

* add monotime on zephyr

Co-authored-by: Jaremy Creechley <jaremy.creechley@panthalassa.com>
(cherry picked from commit 6976d18519)

lib/std/monotimes.nim

@@ -76,6 +76,10 @@ when defined(js):
 elif defined(posix) and not defined(osx):
   import posix
 
+when defined(zephyr):
+  proc k_uptime_ticks(): int64 {.importc: "k_uptime_ticks", header: "<kernel.h>".}
+  proc k_ticks_to_ns_floor64(ticks: int64): int64 {.importc: "k_ticks_to_ns_floor64", header: "<kernel.h>".}
+
 elif defined(windows):
   proc QueryPerformanceCounter(res: var uint64) {.
     importc: "QueryPerformanceCounter", stdcall, dynlib: "kernel32".}
@@ -98,6 +102,9 @@ proc getMonoTime*(): MonoTime {.tags: [TimeEffect].} =
     mach_timebase_info(machAbsoluteTimeFreq)
     result = MonoTime(ticks: ticks * machAbsoluteTimeFreq.numer div
       machAbsoluteTimeFreq.denom)
+  elif defined(zephyr):
+    let ticks = k_ticks_to_ns_floor64(k_uptime_ticks())
+    result = MonoTime(ticks: ticks)
   elif defined(posix):
     var ts: Timespec
     discard clock_gettime(CLOCK_MONOTONIC, ts)

lib/std/sysrand.nim

@@ -63,7 +63,7 @@ when defined(posix):
   import posix
 
 const
-  batchImplOS = defined(freebsd) or defined(openbsd) or (defined(macosx) and not defined(ios))
+  batchImplOS = defined(freebsd) or defined(openbsd) or defined(zephyr) or (defined(macosx) and not defined(ios))
   batchSize {.used.} = 256
 
 when batchImplOS:
@@ -207,6 +207,16 @@ elif defined(openbsd):
   proc getRandomImpl(p: pointer, size: int): int {.inline.} =
     result = getentropy(p, cint(size)).int
 
+elif defined(zephyr):
+  proc sys_csrand_get(dst: pointer, length: csize_t): cint {.importc: "sys_csrand_get", header: "<random/rand32.h>".}
+    # Fill the destination buffer with cryptographically secure
+    # random data values
+    # 
+
+  proc getRandomImpl(p: pointer, size: int): int {.inline.} =
+    # 0 if success, -EIO if entropy reseed error
+    result = sys_csrand_get(p, csize_t(size)).int
+
 elif defined(freebsd):
   type cssize_t {.importc: "ssize_t", header: "<sys/types.h>".} = int