ADD_ABI.md

Adding an ABI

Overview

The ABI descriptions in Sibyl are quite simple for now. Their are located in sibyl/abi, and all inherits from sibyl.abi.abi:ABI.

The convention is to regroup them by relative architecture.

Add an ABI

Here is a commented fake ABI, where arguments are first passed by registers, and then by stack:

class ABI_CUSTOM(abi.ABIRegsStack):

	# Map argument number -> register name
    regs_mapping = ["A0", "A1", "A2", "A3"]
	# Associate this ABI to a given architecture, to be used when this
	# achitecture is recognized
    arch = ["mips32b", "mips32l"]

	# Indicate how the return address has to be set (stack, specific register,
	# ...)
    def set_ret(self, ret_addr):
        self.jitter.cpu.RA = ret_addr

	# Indicate how an element is push on the stack, for stack based arguments
    def vm_push(self, element):
        self.jitter.push_uint32_t(element)

Finally, the class just has to be added to the sibyl.abi:ABIS list to be considered.