IMGJulian commented on a change in pull request #474: PIC32: Fix stack align
URL: https://github.com/apache/mynewt-core/pull/474#discussion_r131878603
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File path: kernel/os/include/os/arch/pic32/os/os_arch.h
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@@ -38,7 +38,8 @@ typedef uint32_t os_sr_t;
/* Stack type, aligned to a 32-bit word. */
#define OS_STACK_PATTERN (0xdeadbeef)
-typedef uint32_t os_stack_t;
+/* uint64_t in an attempt to get the stack 8 aligned */
+typedef uint64_t os_stack_t;
Review comment:
That makes a lot of sense. I have just dug out my old attempt at that code
and remembered another problem I had with it: I am storing my lazy FPU context
as an offset to the top of the stack (which must be aligned). The actual top of
the stack cannot be modified in the `os_arch_task_stack_init()` function as it
is overwritten shortly after. Do you know how much would be broken by changing
this (in os_task.c):
```
t->t_stackptr = os_arch_task_stack_init(t, &stack_bottom[stack_size],
stack_size);
t->t_stacktop = &stack_bottom[stack_size];
t->t_stacksize = stack_size;
```
to this:
```
t->t_stacktop = &stack_bottom[stack_size];
t->t_stacksize = stack_size;
t->t_stackptr = os_arch_task_stack_init(t, &stack_bottom[stack_size],
stack_size);
```
? (You could even get rid of 2 args to `os_arch_task_stack_init()`).
The alternative is computing the alignment every time I want to access the
FPU context.
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