xiaoxiang781216 commented on a change in pull request #2042:
URL: https://github.com/apache/incubator-nuttx/pull/2042#discussion_r508339111
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File path: arch/arm/src/cxd56xx/cxd56_irq.c
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@@ -115,17 +112,17 @@ static uint64_t g_intstack_alloc[INTSTACK_ALLOC >> 3];
const uint32_t g_cpu_intstack_top[CONFIG_SMP_NCPUS] =
{
- (uint32_t)g_intstack_alloc + INTSTACK_SIZE,
+ (uint32_t)g_intstack_alloc + INTSTACK_SIZE - 8,
Review comment:
> I think that adjustment is necessary to get the address of the last
element in the stack, at least for the case of how g_intstack_alloc is
allocated (a 64bit array)
In most location, -8 is used to calculate the initial stack pointer, but the
convention is always sub the stack pointer first before access the data on the
stack as AAPCS required. -8 is wrong in this case.
If user want to access the last element he should sub 4/8 manually, or use <
in the loop:
for (i = 0; i < stack_size; i += 4/8)
ARM AAPCS(and many other arch) require that push implement like this:
```
sub sp, #4/#8
str val, [sp]
```
so the pointer should point to after the end of stack. -8 make the code
complexity and waste a little memory, or is there a special reason to do in
this way, @patacongo? I have worked with many RTOS and bootloader, but never
see the type of special code.
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