nrf5340 net core crashes when multiplying 2 uint16_t

[Jocelyn Masserot]

Hi all,

I'm currently trying to get Nimble controller running on the nrf53 net core. All seems fine except that the core is crashing when I multiply 2 uint16_t variables together. When I'm using uint32_t variables the core doesn't crash. 

Is there any constraint regarding the variable alignment?

Here is the code that fails:

uint16_t temp = 2, temp2 = 4;
temp = temp * temp2;

temp is located at address 0x2100d396 and temp2 is at 0x2100d394. When I run the code, it crashes on temp and temp2 multiplication.

Same code with uint32_t that works fine:

uint32_t temp = 2, temp2 = 4;
temp = temp * temp2;

temp is at 0x2100d394 and temp2 at 0x2100d390.

Any idea what I'm missing here? Thanks

Jocelyn

[tesc]

Hi,

Do you have a minimal example of this failing in a project? (That is, a full project, not only the two lines of code?) Also, do you have more details regarding the crash, such as any log, crash log, observations from a debug session, etc.?

Regards,
Terje

[Jocelyn Masserot]

Hi, thanks for your reply.

The code is super simple. I can get the Network core to crash directly from the reset handler:

extern unsigned long _sidata;   /* start address for the initialization values of the .data section. defined in linker script */
extern unsigned long _sdata;    /* start address for the .data section. defined in linker script */
extern unsigned long _edata;    /* end address for the .data section. defined in linker script */
extern unsigned long _sbss;     /* start address for the .bss section. defined in linker script */
extern unsigned long _ebss;     /* end address for the .bss section. defined in linker script */
extern unsigned long _estack;

void Reset_Handler(void)
{
	unsigned long *src, *dest;
	
	src = &_sidata;
	
	for(dest = &_sdata; dest < &_edata; )
	{
		*(dest++) = *(src++);
	}
    
	for(dest = &_sbss; dest < &_ebss; )
	{
		*(dest++) = 0;
	}

	uint16_t temp = 2, temp2 = 4;
	temp = temp * temp2;

	main();
}

The core dump I'm getting:

error   [FAULT]: [************* Hard fault *************]                                     
error   [FAULT]: r0 = 0x4                                                                     
error   [FAULT]: r1 = 0xffffffb8                                                              
error   [FAULT]: r2 = 0x1c                                                                    
error   [FAULT]: r3 = 0x0                                                                     
error   [FAULT]: r12 = 0x2                                                                    
error   [FAULT]: lr = 0x4                                                                     
error   [FAULT]: pc = 0x1016b4f                                                               
error   [FAULT]: psr = 0x1000c0b                                                              
error   [FAULT]: icsr = 0x803                                                                 
error   [FAULT]: bfar = 0xe000ed38                                                            
error   [FAULT]: cfsr = 0x10000                                                               
error   [FAULT]: hfsr = 0x40000000                                                            
error   [FAULT]: mmfar = 0xe000ed34                                                           
error   [FAULT]: sfsr = 0x0                                                                   
error   [FAULT]: sfar = 0x0                                                                   
error   [FAULT]: [**************************************]  

The observation I made so far is that the variable alignment seems to be the culprit.

Thanks,

Jocelyn

[tesc]

Hi,

Please provide the full project for reproduction, not only parts of it.

Regards,
Terje

[Jocelyn Masserot]

Hi,

I'll try to send a full project later today. In the meantime, I've been able to narrow down the investigation. It look like the "smulbb" assembly instruction is the one causing the crash. The following code is also crashing:

__asm volatile 
(
	"ldr r0, =2\n"
	"ldr r1, =2\n"		
	"smulbb r2, r0, r1 \n"
);

Best,

Jocelyn

[Jocelyn Masserot]

I found the issue, I was setting the option -mcpu to cortex-m33 while I should have used cortex-m33+nodsp. 

Thanks for your help.