Here are the classes, structs, unions and interfaces with brief descriptions:

Cansi_color_map_t	Stores the association between ANSI colors and pure VIDEO colors
Cata_device_t	Stores information about an ATA device
Cata_identity_t	IDENTIFY device data (response to 0xEC)
Cbb_free_area_t	Buddy system descriptor: collection of free page blocks. Each block represents 2^k free contiguous page
Cbb_instance_t	Buddy system instance, that represents a memory area managed by the buddy system
Cbb_page_t	The base structure representing a bb page
Cblock_t	Represents a block of memory within the heap. This structure includes metadata for managing memory allocation and free status
Cboot_info_t	Mentos structure to communicate bootloader info to the kernel
Ccpuinfo_t	Contains the information concerning the CPU
Cdirent_t	Directory entry
Celf_header	The elf starting section
Celf_program_header	The elf program header, holding program layout information
Celf_rel_t	Holds information about relocation object (that do not need an addend)
Celf_rela_t	Holds information about relocation object (that need an addend)
Celf_section_header	A section header with all kinds of useful information
Celf_symbol	A symbol itself
Cenv87	Environment information of floating point unit
Cenvxmm	Stores the XMM environment
Cext2_dirent_t	The header of an ext2 directory entry
Cext2_direntry_iterator_t	Iterator for visiting the directory entries
Cext2_direntry_search_t	Structure used when searching for a directory entry
Cext2_filesystem_t	The details regarding the filesystem
Cext2_group_descriptor_t	Entry of the Block Group Descriptor Table (BGDT)
Cext2_inode_t	The ext2 inode
Cext2_superblock_t	The superblock contains all the information about the configuration of the filesystem
Cfile_system_type	Filesystem information
Cfpacc87	Contents of each floating point accumulator
Cgdt_descriptor_t	Data structure representing a GDT descriptor
Cgdt_pointer_t	Data structure used to load the GDT into the GDTR
Cgroup	Contains user group informations
Chashmap_entry_t	Stores information of an entry of the hashmap
Chashmap_t	Stores information of a hashmap
Cheap_header_t	Maps the heap memory to easily accessible values. This structure contains pointers to the list of all blocks and the list of free blocks
Ciattr	Data structure containing attributes of a file
Cidt_descriptor_t	This structure describes one interrupt gate
Cidt_pointer_t	A pointer structure used for informing the CPU about our IDT
Cirq_struct_t	Shared interrupt handlers, stored into a double-linked list
Citimerval	Rappresents a time interval
Ckeymap_t	Defines the mapping of a single scancode towards a set of characters
Ckmem_cache_t	Stores the information of a cache
Ckmem_obj	Structure to represent an individual memory object within a slab
Clist_t	Represent the list
Clistnode_t	Represent the node of a list
Cmalloc_header_t	A structure that holds the information about an allocated chunk of memory through malloc
Cmm_struct_t	Memory Descriptor, used to store details about the memory of a user process
Cmsq_info_t	Message queue management structure
Cmultiboot_aout_symbol_table_t	The symbol table for a.out
Cmultiboot_elf_section_header_table_t	The section header table for ELF
Cmultiboot_info_t	Multiboot information structure
Cmultiboot_memory_map_t	Stores information about memory mapping
Cmultiboot_module_t	Stores information about a module
Cmutex_t	Structure of a mutex
Cndtree_iter_t	Stores data about an NDTree iterator
Cndtree_node_t	Stores data about an NDTree node
Cndtree_t	Stores data about an NDTree
Cpage_dir_entry_t	An entry of a page directory
Cpage_directory_t	A page directory
Cpage_iterator_s	Structure for iterating page directory entries
Cpage_t	Page descriptor. Use as a bitmap to understand the order of the block and if it is free or allocated
Cpage_table_entry_t	An entry of a page table
Cpage_table_t	A page table
Cpalette_entry_t	Structure that simplifies defining a palette
Cpasswd_t	Stores user account information
Cpg_data_t	Data structure to rapresent a memory node. In Uniform memory access (UMA) architectures there is only one node called contig_page_data
Cpg_iter_entry_s	Structure for iterating page table entries
Cprdt_t	Physical Region Descriptor Table (PRDT) entry
Cproc_dir_entry_t	Stores information about a procfs directory entry
Cprocfs_file_t	Information concerning a file
Cprocfs_t	The details regarding the filesystem
Cpt_regs	Interrupt stack frame
Crbtree_iter_t	Stores information for iterating a rbtree
Crbtree_node_t	Stores information of a node
Crbtree_t	Stores information of a rbtree
Crunqueue_t	Structure that contains information about live processes
Csave87	Floating point context
Csavefpu	Stores FPU registers details
Csavexmm	Stores the XMM context
Csched_entity_t	This structure is used to track the statistics of a process
Csched_param	Structure that describes scheduling parameters
Csched_param_t	Structure that describes scheduling parameters
Csem_info_t	Semaphore management structure
CSHA256_ctx_t	Structure that holds context information for SHA-256 operations
Csigaction	Holds the information on how to handle a specific signal
Csigaction_t	Holds the information on how to handle a specific signal
Csighand_t	Describes how each signal must be handled
Csiginfo	Stores information about an occurrence of a specific signal
Csiginfo_t	Stores information about an occurrence of a specific signal
Csigpending_t	Keeps information of pending signals
Csigqueue_t	An entry of the signal queue
Csigset	Structure used to mask and unmask signals
Csigset_t	Structure used to mask and unmask signals
Csigval	Data passed with signal info
Csleep_data	Contains the entry of a wait queue and timespec which keeps trakc of the remaining time
Cstat	Data structure which contains information about a file
Csuper_block_t	A structure that represents an instance of a filesystem, i.e., a mounted filesystem
Ctask_struct	This is our task object. Every process in the system has this, and it holds a lot of information. It’ll hold mm information, it’s name, statistics, etc.
Ctermios	Stores information about a terminal IOs
Cthread_struct_t	Stores the status of CPU and FPU registers
Ctimer_list	Represents the request to execute a function in the future, also known as timer
Ctimespec	Specify intervals of time with nanosecond precision
Ctimeval	Rappresents time
Ctm	Used to get information about the current time
Ctss_entry	Task state segment entry
Ctvec_base_s	Contains all the timers of a single CPU
Cutsname_t	Holds information concerning the machine and the os
Cvfs_file_descriptor_t	Data structure containing information about an open file
Cvfs_file_operations_t	Set of functions used to perform operations on files
Cvfs_file_t	Data structure that contains information about the mounted filesystems
Cvfs_sys_operations_t	Set of functions used to perform operations on filesystem
Cvga_driver_t	VGA driver details
Cvga_font_t	VGA font details
Cvga_mode_t	Structure that holds the information about a VGA mode
Cvga_ops_t	VGA pointers for drawing operations
Cvirt_map_page_manager_t	Virtual mapping manager
Cvirt_map_page_t	Virtual mapping
Cvm_area_struct_t	Virtual Memory Area, used to store details of a process segment
Cwait_queue_entry_t	Entry of the waiting queue
Cwait_queue_head_t	Head of the waiting queue
Cxmmacc	Contents of each SSE extended accumulator
Czone_t	Data structure to differentiate memory zone