RISCV-CLLD

Uni exercise - Circular Doubly-Linked List implementation in RISCV 64 Assembly

Program workflow:

• Create head node with ASCII value 'R'
• Add node with ASCII value 'V' to the tail
• Add node with ASCII value 'I' to the tail
• Add node with ASCII value 'S' to the tail
• Add node with ASCII value 'C' to the tail
• Traverse the list nodes and print their values
• Remove the node with 'V' value from the list
• Exit with exit code 0

Task specifications:

• No pseudoinstructions or libraries are allowed to be used.
• Registers only called by their ABI names
• Function and syscall return values must always be checked for error. if syscall returns error value, the program must terminate with exit code 125
• The program must exit only under _start label

Node structure:

• val (8 Bytes): node value
• next (8 Bytes): address of the next node
• prev (8 Bytes): address of the previous node

Functions that must be implemented:

• alloc_node()

  args: a0: val

  description: Allocates memory for an empty node structure, sets val MSByte to 0xA and other bytes to value specified in (a0)

  disclaimer: next and prev values must be not NULL and set to itself

  return: starting address of the allocated node

• add_tail()

  args: a0: address of head node a1: address of the new node

  description: adds the new node (a1) to the tail of a list that starts from head node (a0)

• del_node()

  args: a0: address of head node a1: address of node to be deleted

  description: deletes node with address (a1) from list starting from head node (a0)

  return: (-1) if the tobe-deleted node isn't found or list head node address, otherwise.

• print_list()

  args: a0: address of head node

  description: traverses every node of a list starting from head (a0) and prints node->val to the terminal

  return: (-1) at first print fail or the number of bytes written at last