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mm:initialize ensure alignment. 

Broken by 635cfa.

   On an stm32 the heap is formed from
   const uintptr_t g_idle_topstack = HEAP_BASE;
   where HEAP_BASE is &_bss + CONFIG_IDLE_STACKSIZE.

   Both these values are not deterministic. One
   comes from the compiler, the other the system
   configurator.

   a 3 byte bss and 250 byte stack would lead to
   and unaligned address used as the heap to be.

   The compiler used clever `strd r1,r3,[r5,#8]` to
   store 2 values in one memory cycle into the
   heap_impl struct. Resulting in a hardfault.

   Change the amount of bss or the CONFIG_IDLE_STACKSIZE
   could lead to a non-functional NuttX system.
This commit is contained in:
David Sidrane 2021-05-19 13:02:13 -07:00 committed by Xiang Xiao
parent 2217d2f0d3
commit 85f0bc591e
1 changed files with 9 additions and 3 deletions
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12
mm/mm_heap/mm_initialize.c
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@ -165,17 +165,23 @@ void mm_initialize(FAR struct mm_heap_s *heap, FAR void *heapstart,
size_t heapsize)
{
FAR struct mm_heap_impl_s *heap_impl;
int i;
uintptr_t heap_adj;
int i;
minfo("Heap: start=%p size=%zu\n", heapstart, heapsize);
/* First ensure the memory to be used is aligned */
heap_adj = MM_ALIGN_UP((uintptr_t) heapstart);
heapsize -= heap_adj - (uintptr_t) heapstart;
/* Reserve a block space for mm_heap_impl_s context */
DEBUGASSERT(heapsize > sizeof(struct mm_heap_impl_s));
heap->mm_impl = (FAR struct mm_heap_impl_s *)heapstart;
heap->mm_impl = (FAR struct mm_heap_impl_s *)heap_adj;
heap_impl = heap->mm_impl;
heapsize -= sizeof(struct mm_heap_impl_s);
heapstart = (FAR char *)heapstart + sizeof(struct mm_heap_impl_s);
heapstart = (FAR char *)heap_adj + sizeof(struct mm_heap_impl_s);
/* The following two lines have cause problems for some older ZiLog
* compilers in the past (but not the more recent). Life is easier if we