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AP_HAL_Linux: Thread: make sure pointer is aligned

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Implementation of alloca() is very much architecture and compiler
dependent. Avoid the case in which it could return a non-aligned
pointer, which would mean Thread::_poison_stack() would do the wrong
thing.
This commit is contained in:
Lucas De Marchi 2016-05-19 12:36:11 -03:00
parent 7e49d0c53f
commit 359417d544
1 changed files with 11 additions and 1 deletions
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12
libraries/AP_HAL_Linux/Thread.cpp
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@ -55,6 +55,12 @@ bool Thread::_run()
return true; return true;
} }
/* Round up to the specified alignment */
static inline void *align_to(void *p, size_t align)
{
return (void *)(((uintptr_t)p + align - 1) & ~(align - 1));
}
void Thread::_poison_stack() void Thread::_poison_stack()
{ {
pthread_attr_t attr; pthread_attr_t attr;
@ -75,7 +81,7 @@ void Thread::_poison_stack()
* protects the end */ * protects the end */
end = (uint32_t *)stackp; end = (uint32_t *)stackp;
begin = end + stack_size; begin = end + stack_size;
curr = (uint32_t *)alloca(sizeof(uint32_t)); curr = (uint32_t *)align_to(alloca(sizeof(uint32_t)), alignof(uint32_t));
/* if curr is closer to @end, the stack actually grows from low to high /* if curr is closer to @end, the stack actually grows from low to high
* virtual address: this is because this function should be executing very * virtual address: this is because this function should be executing very
@ -92,6 +98,10 @@ void Thread::_poison_stack()
} else { } else {
end += guard_size; end += guard_size;
/* we aligned curr to the up boundary, make sure this didn't cause us
* to lose some bytes */
curr--;
for (p = end; p < curr; p++) { for (p = end; p < curr; p++) {
*p = STACK_POISON; *p = STACK_POISON;
} }