why my mutex is not recognised as kernel object

[pasuzw]

Hi Everyone

Just would like to see if anybody has similar issues or knows how I could check further ?

My project has one user thread that wants to access a mutex but I got error like the following:

Zephyr RTOS->|syscall z_vrfy_k_mutex_lock failed check: access denied
Zephyr RTOS->|r0/a1: 0x00000000 r1/a2: 0x00000000 r2/a3: 0x00000000
Zephyr RTOS->|r3/a4: 0x00000000 r12/ip: 0x00000000 r14/lr: 0x00000000
Zephyr RTOS->| xpsr: 0x00000000
Zephyr RTOS->|Faulting instruction address (r15/pc): 0x00000000
Zephyr RTOS->|>>> ZEPHYR FATAL ERROR 3: Kernel oops on CPU 0
Zephyr RTOS->|Current thread: 20000200 (read_only_task)

some background info:

• Nordic_nRF_Connect_SDK v2.4.2 which has zephyr 3.3.99.
• MPU enabled
• USER SPACE enabled
• nRF5283 CORTEX-M4

My definition for the mutex in uart.c file:
K_MUTEX_DEFINE(my_mutex);

and the user_thread.c has the following code to create a user thread, grant access to my mutex for the user thread:

extern struct k_mutex rs_rtos_debug_uart_mutex;
void read_only_task_create(void)
{
k_mem_domain_init(&app0_domain, ARRAY_SIZE(app_parts), app_parts);
//functin to create user thread
k_mem_domain_add_thread(&app0_domain, ro_task_handle.thread_id);
k_object_access_grant(&rs_rtos_debug_uart_mutex, ro_task_handle.thread_id);
k_thread_start(ro_task_handle.thread_id);
}

What I found so far ?
z_vrfy_k_mutex_lock() is checking my mutex pointer and report the follow logging info:

20010ca8 is not a valid
address is not a known kernel object

According to my map file, my mutex is placed at address 0x20010ca8

_.k_mutex.static.my_mutex
0x0000000020010ca8 0x14 app/libapp.a(uart.c.obj)

As far as I can tell, the z_object_find(&my_mutex) is returnning NULL which caused the error.
I understood there is a python file gen_kobject_list.py is looking for all kernel objects and create a hash table for runtime check used in z_object_find(). This python file gives me this ->
gen_kobject_list.py: symbol 'my_mutex' at 0x20010cd4 contains 1 object(s)
The build/zephyr/kobject_hash.c confirms that 0x20010cd4 is stored in the hash table.

My vscode debugger tells me that the address of my_mutex passed into z_object_find() is 0x20010ca8, the same in the map file. Then z_object_find() could not find it because the hash table generated by gen_kobject_list.py only has 0x20010cd4 for my mutex.

It seems weird to me the gen_kobject_list.py found the symbol of my_mutex from elf file , but it is not the same address as in the final map file.

Any body could help me here ?

Thanks in advance.

[jukkar]

I think you need to use sys_mutex* API from userspace.

[pasuzw]

Thanks for the suggestion. It solves my problem.