bsd-user: Deal with mmap where start > reserved_va

Fixes: f12294b5bd ("bsd-user: Use page_find_range_empty for mmap_find_vma_reserved")
Signed-off-by: Bingwu Zhang <xtex@astrafall.org>
Reviewed-by: Helge Deller <deller@gmx.de>
Reviewed-by: Warner Losh <imp@bsdimp.com>
Signed-off-by: Helge Deller <deller@gmx.de>

bsd-user/mmap.c

@@ -258,12 +258,14 @@ abi_ulong mmap_next_start = TASK_UNMAPPED_BASE;
 static abi_ulong mmap_find_vma_reserved(abi_ulong start, abi_ulong size,
                                         abi_ulong alignment)
 {
-    abi_ulong ret;
+    abi_ulong ret = -1;
 
-    ret = page_find_range_empty(start, reserved_va, size, alignment);
+    if (start <= reserved_va) {
+        ret = page_find_range_empty(start, reserved_va, size, alignment);
+    }
     if (ret == -1 && start > TARGET_PAGE_SIZE) {
         /* Restart at the beginning of the address space. */
-        ret = page_find_range_empty(TARGET_PAGE_SIZE, start - 1,
+        ret = page_find_range_empty(TARGET_PAGE_SIZE, MIN(start - 1, reserved_va),
                                     size, alignment);
     }