Zephyr User Mode Support (#3650)

Add support for the [Zephyr Usermode](https://docs.zephyrproject.org/latest/kernel/usermode/index.html)
to the Zephyr port.

The following changes are applied:
- Fix `signbit`, check if it is defined already and only implement it, if not
- Introduce `sys_mutex` and `sys_sem` in favour of `k_mutex` and `k_sem`, when `CONFIG_USERMODE` is enabled
- Remove the installation of the `_stdout_hook_iwasm()` when `CONFIG_USERMODE` is enabled, otherwise this
  causes MPU errors since the std hook is in the kernel space
- Add a thread name for debugging

Author: mxsdlr

core/shared/platform/zephyr/platform_internal.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (C) 2019 Intel Corporation.  All rights reserved.
+ * SPDX-FileCopyrightText: 2024 Siemens AG (For Zephyr usermode changes)
  * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  */
 
@@ -18,7 +19,6 @@
 #include <misc/printk.h>
 #endif
 #else /* else of KERNEL_VERSION_NUMBER < 0x030200 */
-#include <zephyr/kernel.h>
 #include <zephyr/sys/printk.h>
 #endif /* end of KERNEL_VERSION_NUMBER < 0x030200 */
 
@@ -37,19 +37,26 @@
 #endif
 
 #if KERNEL_VERSION_NUMBER < 0x030200 /* version 3.2.0 */
+#include <zephyr.h>
 #include <net/net_pkt.h>
 #include <net/net_if.h>
 #include <net/net_ip.h>
 #include <net/net_core.h>
 #include <net/net_context.h>
 #else /* else of KERNEL_VERSION_NUMBER < 0x030200 */
+#include <zephyr/kernel.h>
 #include <zephyr/net/net_pkt.h>
 #include <zephyr/net/net_if.h>
 #include <zephyr/net/net_ip.h>
 #include <zephyr/net/net_core.h>
 #include <zephyr/net/net_context.h>
 #endif /* end of KERNEL_VERSION_NUMBER < 0x030200 */
 
+#ifdef CONFIG_USERSPACE
+#include <zephyr/sys/mutex.h>
+#include <zephyr/sys/sem.h>
+#endif /* end of CONFIG_USERSPACE */
+
 #if KERNEL_VERSION_NUMBER >= 0x030300 /* version 3.3.0 */
 #include <zephyr/cache.h>
 #endif /* end of KERNEL_VERSION_NUMBER > 0x030300 */
@@ -64,18 +71,47 @@
 #endif
 #endif
 
+#ifdef signbit /* probably since Zephyr v3.5.0 a new picolib is included */
+#define BH_HAS_SIGNBIT 1
+#endif
+
 #ifndef BH_PLATFORM_ZEPHYR
 #define BH_PLATFORM_ZEPHYR
 #endif
 
+// Synchronization primitives for usermode
+#ifdef CONFIG_USERSPACE
+#define mutex_t struct sys_mutex
+#define mutex_init(mtx) sys_mutex_init(mtx)
+#define mutex_lock(mtx, timeout) sys_mutex_lock(mtx, timeout)
+#define mutex_unlock(mtx) sys_mutex_unlock(mtx)
+
+#define sem_t struct sys_sem
+#define sem_init(sem, init_count, limit) sys_sem_init(sem, init_count, limit)
+#define sem_give(sem) sys_sem_give(sem)
+#define sem_take(sem, timeout) sys_sem_take(sem, timeout)
+#define sem_count_get(sem) sys_sem_count_get(sem)
+#else /* else of CONFIG_USERSPACE */
+#define mutex_t struct k_mutex
+#define mutex_init(mtx) k_mutex_init(mtx)
+#define mutex_lock(mtx, timeout) k_mutex_lock(mtx, timeout)
+#define mutex_unlock(mtx) k_mutex_unlock(mtx)
+
+#define sem_t struct k_sem
+#define sem_init(sem, init_count, limit) k_sem_init(sem, init_count, limit)
+#define sem_give(sem) k_sem_give(sem)
+#define sem_take(sem, timeout) k_sem_take(sem, timeout)
+#define sem_count_get(sem) k_sem_count_get(sem)
+#endif /* end of CONFIG_USERSPACE */
+
 #define BH_APPLET_PRESERVED_STACK_SIZE (2 * BH_KB)
 
 /* Default thread priority */
 #define BH_THREAD_DEFAULT_PRIORITY 7
 
 typedef struct k_thread korp_thread;
 typedef korp_thread *korp_tid;
-typedef struct k_mutex korp_mutex;
+typedef mutex_t korp_mutex;
 typedef unsigned int korp_sem;
 
 /* korp_rwlock is used in platform_api_extension.h,
@@ -87,7 +123,7 @@ typedef struct {
 struct os_thread_wait_node;
 typedef struct os_thread_wait_node *os_thread_wait_list;
 typedef struct korp_cond {
-    struct k_mutex wait_list_lock;
+    mutex_t wait_list_lock;
     os_thread_wait_list thread_wait_list;
 } korp_cond;
 
@@ -120,11 +156,14 @@ float fmaxf(float x, float y);
 float rintf(float x);
 float fabsf(float x);
 float truncf(float x);
-int signbit(double x);
 int isnan(double x);
 double pow(double x, double y);
 double scalbn(double x, int n);
 
+#ifndef BH_HAS_SIGNBIT
+int signbit(double x);
+#endif
+
 unsigned long long int strtoull(const char *nptr, char **endptr, int base);
 double strtod(const char *nptr, char **endptr);
 float strtof(const char *nptr, char **endptr);

core/shared/platform/zephyr/zephyr_platform.c

@@ -1,5 +1,6 @@
 /*
  * Copyright (C) 2019 Intel Corporation.  All rights reserved.
+ * SPDX-FileCopyrightText: 2024 Siemens AG (For Zephyr usermode changes)
  * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  */
 
@@ -35,12 +36,14 @@ disable_mpu_rasr_xn(void)
 #endif /* end of CONFIG_ARM_MPU */
 #endif
 
+#ifndef CONFIG_USERSPACE
 static int
 _stdout_hook_iwasm(int c)
 {
     printk("%c", (char)c);
     return 1;
 }
+#endif
 
 int
 os_thread_sys_init();
@@ -51,9 +54,11 @@ os_thread_sys_destroy();
 int
 bh_platform_init()
 {
+#ifndef CONFIG_USERSPACE
     extern void __stdout_hook_install(int (*hook)(int));
     /* Enable printf() in Zephyr */
     __stdout_hook_install(_stdout_hook_iwasm);
+#endif
 
 #if WASM_ENABLE_AOT != 0
 #ifdef CONFIG_ARM_MPU