Use SDRAM for a very limited sort of heap.

1 files changed, 89 insertions, 0 deletions

diff --git a/sdram-malloc.c b/sdram-malloc.c
new file mode 100644
index 0000000..0c5813a
--- /dev/null
+++ b/sdram-malloc.c
@@ -0,0 +1,89 @@
+/*
+ * sdram_malloc.c
+ * --------------
+ * Use SDRAM for a very limited sort of heap.
+ *
+ * Copyright (c) 2016, NORDUnet A/S All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ * - Redistributions of source code must retain the above copyright notice,
+ *   this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ *
+ * - Neither the name of the NORDUnet nor the names of its contributors may
+ *   be used to endorse or promote products derived from this software
+ *   without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+ * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+ * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+ * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* Allocate memory from SDRAM1. This is not a general allocator, and
+ * should only be used with the greatest of caution and care.
+ *
+ * This is intended for allocating memory that will never be freed
+ * (e.g. thread stack buffers), or for memory that will be freed as soon
+ * as the requesting function is done with it (e.g. file upload
+ * buffers).
+ *
+ * Memory should be freed in reverse order of allocation (most
+ * recent first).
+ *
+ * There are no memory block control fields, so no protection to ensure
+ * that memory that is freed is actually the memory that was allocated.
+ */
+
+#include <stddef.h>
+#include <stdint.h>
+
+/* end of variables declared with __attribute__((section(".sdram1"))) */
+extern uint8_t _esdram1 __asm ("_esdram1");
+static uint8_t * const sdram_heap_base = &_esdram1;
+
+/* end of sdram1 section */
+extern uint8_t __end_sdram1 __asm ("__end_sdram1");
+static uint8_t * const sdram_heap_end = &__end_sdram1;
+
+/* current heap top */
+static uint8_t *sdram_heap = &_esdram1;
+
+/* Allocate some memory. Allocations are not padded, because kermit will
+ * call repeatedly to write blocks of data to a "file". OTOH, it's a good
+ * idea to allocate padding after the last write, so the next allocation
+ * will be aligned.
+ */
+uint8_t *sdram_malloc(size_t size)
+{
+    uint8_t *p = sdram_heap;
+
+    if (p + size > sdram_heap_end)
+        return NULL;
+
+    sdram_heap += size;
+    return p;
+}
+
+/* Free some memory allocated from sdram. This does only the most basic of
+ * sanity checks.
+ */
+void sdram_free(uint8_t *s)
+{
+    if (s < sdram_heap_base || s >= sdram_heap_end)
+        return;
+    if (s < sdram_heap)
+        sdram_heap = s;
+}