Sanitizing sbrk with stack stuff.

1 files changed, 5 insertions, 3 deletions

diff --git a/os/src/sbrk.c b/os/src/sbrk.c
index 221c809..4208b2e 100644
--- a/os/src/sbrk.c
+++ b/os/src/sbrk.c
@@ -8,13 +8,15 @@
 
 // Mostly stolen from mbed-freertos
 
-extern unsigned int __heap_start, __heap_end;
+extern uintptr_t __heap_start, __heap_end;
+extern uintptr_t __stack_start __attribute__((weak));
 
 /* Low-level bulk RAM allocator -- used by Newlib's Malloc */
 void *heap_end = NULL;
 PRIVILEGED_FUNCTION void *_sbrk_r(struct _reent *ptr, ptrdiff_t incr)
 {
     void *prev_heap_end, *next_heap_end, *ret;
+    void *stack_min = (void *)(__stack_start ? __stack_start : __heap_end);
 
     taskENTER_CRITICAL();
     {
@@ -27,10 +29,10 @@ PRIVILEGED_FUNCTION void *_sbrk_r(struct _reent *ptr, ptrdiff_t incr)
         prev_heap_end = heap_end;
 
         /* Align to always be on 8-byte boundaries */
-        next_heap_end = (void *)((((unsigned int)heap_end + incr) + 7) & ~7);
+        next_heap_end = (void *)((((uintptr_t)heap_end + incr) + 7) & ~7);
 
         /* Check if this allocation would exceed the end of the ram - would probably get into the stack first however */
-        if (next_heap_end > (void *)&__heap_end)
+        if (next_heap_end > stack_min)
         {
             ptr->_errno = ENOMEM;
             ret = NULL;