Re: Bitmap size in buddy_alloc.cpp

On Tue, 2011-05-03 at 13:26 +0200, Christian Ehrhardt wrote:

Access to the _free_map bitmap in the buddy allocator is possible beyond Max_mem when checking the free bit of the buddy. Thus bit bitmap size should be aligned to Max_size not Min_size.

regards   Christian

diff --git a/src/kernel/fiasco/src/kern/buddy_alloc.cpp b/src/kernel/fiasco/src/kern/buddy_alloc.cpp index 96f2821..51e1239 100644 --- a/src/kernel/fiasco/src/kern/buddy_alloc.cpp +++ b/src/kernel/fiasco/src/kern/buddy_alloc.cpp @@ -55,7 +55,7 @@ public:

private: Head *_free[Num_sizes];

• Bitmap<(Max_mem+Min_size-1)/Min_size> _free_map;

• Bitmap<(Max_mem+Max_size-1)/Min_size> _free_map;

};

Tanks, however, the fix is somehow different, we only need a single extra bit in the case when Max_mem is not a multiple of Max_size (not the case in Fiasco, 64MB and 128kB).

Anyway, good point in general.