[PATCH] lib: sbi: Add runtime stack overrun detection

[Andreas Schwab]

On Nov 18 2025, Bo Gan wrote:

> Hi Xiang,
>
> On 11/17/25 20:19, Xiang W wrote:
>> +	if (sp < stack_start || sp > stack_end) {
>> +		/* Reset SP to output error messages */
>> +		asm volatile("mv sp, %0"::"r"(stack_end));
>
> I don't think it's safe to switch stack in C function. I know you want
> to avoid re-entrant, but do it in C function is way too risky. Better
> have an asm wapper over this function and do it before invoking the C
> portion.

The GCC docs makes this explicitly undefined:

     Another restriction is that the clobber list should not contain the
    stack pointer register.  This is because the compiler requires the value
    of the stack pointer to be the same after an 'asm' statement as it was
    on entry to the statement.  However, previous versions of GCC did not
    enforce this rule and allowed the stack pointer to appear in the list,
    with unclear semantics.  This behavior is deprecated and listing the
    stack pointer may become an error in future versions of GCC.

-- 
Andreas Schwab, SUSE Labs, schwab at suse.de
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