Document 2

XV6—MMAP-PART2 MMAP : We created a base address MMAPBASE (0x40000000) which is half of the KERNELBASE address. In mman.h we defined the flags for mmap and a struct maplist. Maplist keeps track of the memory mappings allocated by mmap. -#define PROT_WRITE 1 -#define MAP_FILE 1 -#define MAP_ANONYMOUS 0 -struct maplist { - struct maplist *next; - void *addr; - int len; - int prot; - int flags; - int offset; - int fd; - int allocated; -}; In proc.h , we add a reference to the head of the maplist as part of the struct proc. In proc.c, userinit() function we initialize the head of the map list to 0 and in fork() function, we added a logic such that the child processes inherit the map list from parent processes. We added a new file mmap.c containing the below methods. void *mmap(void *addr, uint length, int prot, int flags, int fd, int offset): Inputs: addr - suggestion for starting address, mmap will round up to page aligned addr if needed length- length of region to allocate (in bytes) prot - protection level on mapped region flags - info flags for mapped region fd - file descriptors offset- offset for a file-backed allocation Returns: starting address of the newly mapped  Used flags (MAP_ANONYMOUS, MAP_FILE) to check the type of memory being mapped. If the memory being mapped is related to a file, then we checked for any errors in fd.  Then we incremented the ref count of the file pointer using filedup and did a fileseek on the incremented ref count file pointer. int munmap(void *addr, uint length): munmap takes the address and length given. It will check the maplist to see if the address and the length are valid and match. If they match, it will deallocate the memory from the current process. We then added the deallocuvm() to unmap the