[incubator-nuttx] branch master updated: mm:initialize ensure alignment.

[xi...@apache.org]

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xiaoxiang pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/incubator-nuttx.git


The following commit(s) were added to refs/heads/master by this push:
     new 85f0bc5  mm:initialize ensure alignment.
85f0bc5 is described below

commit 85f0bc591e6cecd616c01d06a4abe943a71f7faf
Author: David Sidrane <Da...@NscDg.com>
AuthorDate: Wed May 19 13:02:13 2021 -0700

    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.
---
 mm/mm_heap/mm_initialize.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/mm/mm_heap/mm_initialize.c b/mm/mm_heap/mm_initialize.c
index 62759e9..0801eae 100644
--- a/mm/mm_heap/mm_initialize.c
+++ b/mm/mm_heap/mm_initialize.c
@@ -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