[U-Boot] [PATCH v5 2/2] dlmalloc: fix malloc range at end of ram

[Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>]

If the malloc range passed to mem_malloc_init() is at the end of address
range and 'start + size' overflows to 0, following allocations fail as
mem_malloc_end is zero (which looks like uninitialized).

Fix this by subtracting 1 of 'start + size' overflows to zero.

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
---

Changes in v5:
- this patch was 1/2 in v4 but is now 2/2 as the 2nd patch of v4 has
  already been accepted
- rearrange the code to make it only 8 bytes plus in code size for arm
  (which fixes smartweb SPL overflowing)

 common/dlmalloc.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/common/dlmalloc.c b/common/dlmalloc.c
index 6f12a18d54..38859ecbd4 100644
--- a/common/dlmalloc.c
+++ b/common/dlmalloc.c
@@ -601,8 +601,12 @@ void *sbrk(ptrdiff_t increment)
 void mem_malloc_init(ulong start, ulong size)
 {
 	mem_malloc_start = start;
-	mem_malloc_end = start + size;
 	mem_malloc_brk = start;
+	mem_malloc_end = start + size;
+	if (size > mem_malloc_end) {
+		/* overflow: malloc area is at end of address range */
+		mem_malloc_end--;
+	}
 
 	debug("using memory %#lx-%#lx for malloc()\n", mem_malloc_start,
 	      mem_malloc_end);
-- 
2.17.1