uC/OS-III - Fix stack peak usage when using redzone

[liamOrndorff]

When redzone stack protection is enabled the 'Stack Peak Usage' column displays all the stacks with 100% peak usage. The peak stack usage calculation needs to skip past the redzone before scanning for the first non-zero byte.

[haneefdm]

@github0null can hopefully look at this.

[PhilippHaefele]

Hi @liamOrndorff,

what`s the pattern of the redzone and what is the pattern of the stack itself?

I`m maybe able to help a little bit here too.

[github0null]

@PhilippHaefele

I did some research.

If user enabled OS_CFG_TASK_STK_REDZONE_EN. Some magic words will be filled at the end of the stack, this way, it can be determined whether the stack will overflow by checking whether the magic word has been overridden.

This function affects the following judgment conditions:

rtos-views/src/rtos/rtos-ucosiii.ts

Line 570 in 38dc7e8

if (stackInfo.bytes[start] !== stackPattern) {

By default, the magic word is 0x5432DCBAABCD2345UL.

The following is a partial code snippet of redzone (taken from the ucos-iii source code)

#define  OS_STACK_CHECK_VAL                 0x5432DCBAABCD2345UL

#if (OS_CFG_TASK_STK_REDZONE_EN > 0u)
void  OS_TaskStkRedzoneInit (CPU_STK       *p_base,
                             CPU_STK_SIZE   stk_size)
{
    CPU_STK_SIZE   i;


#if (CPU_CFG_STK_GROWTH == CPU_STK_GROWTH_HI_TO_LO)
   (void)stk_size;                                              /* Prevent compiler warning for not using 'stk_size'    */

    for (i = 0u; i < OS_CFG_TASK_STK_REDZONE_DEPTH; i++) {
        *(p_base + i) = (CPU_DATA)OS_STACK_CHECK_VAL;
    }
#else
    for (i = 0u; i < OS_CFG_TASK_STK_REDZONE_DEPTH; i++) {
        *(p_base + stk_size - 1u - i) = (CPU_DATA)OS_STACK_CHECK_VAL;
    }
#endif
}
#endif


#if (OS_CFG_TASK_STK_REDZONE_EN > 0u)
CPU_BOOLEAN   OS_TaskStkRedzoneChk (CPU_STK       *p_base,
                                    CPU_STK_SIZE   stk_size)
{
    CPU_INT32U  i;


#if (CPU_CFG_STK_GROWTH == CPU_STK_GROWTH_HI_TO_LO)
   (void)stk_size;                                              /* Prevent compiler warning for not using 'stk_size'    */

    for (i = 0u; i < OS_CFG_TASK_STK_REDZONE_DEPTH; i++) {
        if (*p_base != (CPU_DATA)OS_STACK_CHECK_VAL) {
            return (OS_FALSE);
        }
        p_base++;
    }
#else
    p_base = p_base + stk_size - 1u;
    for (i = 0u; i < OS_CFG_TASK_STK_REDZONE_DEPTH; i++) {
        if (*p_base != (CPU_DATA)OS_STACK_CHECK_VAL) {
            return (OS_FALSE);
        }
        p_base--;
    }
#endif

    return (OS_TRUE);
}
#endif

The peak stack usage calculation needs to skip past the redzone before scanning for the first non-zero byte.

Now i have encountered a problem. The size of this skipped item cannot be obtained through the evaluate function because OS_CFG_TASK_STK_REDZONE_DEPTH is just a preprocessor macro, not a symbol.

[PhilippHaefele]

Thanks for the information. So I would suggest an option to set the ignored width that must be ignored.

[PhilippHaefele]

@github0null @liamOrndorff Is anyone of you willing to contribute such feature to ignore a (configurable) range at the end of the stack?

[github0null]

@github0null @liamOrndorff IS anyone of you willing to contribute such feature to ignore a (configurable) range at the end of the stack?

Sorry, I'm on vacation at the moment. I'll make an update later.