implementing my own dynamic memory allocator in C

Hello, I need to build my own dynamic memory allocator (malloc, free, realloc). I was given a tar file and project writeup of everything I would need to complete the project. i am not allowed to use any of the built-in memory allocation functions. I have to create an explicit free list allocator with first-fit placement, LIFO, with backward coalescing only and block splitting without creating splinters.