buflib: Add crc field protecting buflib cookie integrity

This should catch the case of buffer misuse which results
in corrupted cookie of next allocation. The check is performed
on move_block() so it may be a bit late.

There is buflib_check_valid() provided which checks the
integrity of all cookies for given context.
On DEBUG build with --sdl-thread this check is carried out
for core_ctx on every context switch to catch problems earlier.

Change-Id: I999d4576084592394e3dbd3bdf0f32935ff5f601
Reviewed-on: http://gerrit.rockbox.org/711
Reviewed-by: Thomas Martitz <kugel@rockbox.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/firmware/include/buflib.h b/firmware/include/buflib.h
index 0b26c04bcd..171ab5bcd7 100644
--- a/firmware/include/buflib.h
+++ b/firmware/include/buflib.h
@@ -40,6 +40,7 @@ union buflib_data
     struct buflib_callbacks* ops;
     char* alloc;
     union buflib_data *handle;
+    uint32_t crc;
 };
 
 struct buflib_context
@@ -346,4 +347,9 @@ int buflib_get_num_blocks(struct buflib_context *ctx);
  */
 void buflib_print_block_at(struct buflib_context *ctx, int block_num,
                             char* buf, size_t bufsize);
+
+/**
+ * Check integrity of given buflib context
+ */
+void buflib_check_valid(struct buflib_context *ctx);
 #endif