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#!/usr/bin/env python
import sys
from llvmcpy import llvm
def main():
context = llvm.get_global_context()
# Load and parse the input file
buffer = llvm.create_memory_buffer_with_contents_of_file(sys.argv[1])
module = context.parse_ir(buffer)
# Identify the CSV (global variable) for the register containing the syscall
# number (r7 for ARM)
r7 = module.get_named_global("r7")
# Prepare requirements to build our call to dprintf
# 1) Identify the dprintf function (prototype)
dprintf = module.get_named_function("dprintf")
# 2) Create an integer constant for stderr
two = context.int32_type().const_int(2, True)
# 3) Create the message to print
message_str = context.const_string("%d\n", 4, True)
message = module.add_global(message_str.type_of(), "message")
message.set_initializer(message_str)
message_ptr = message.const_bit_cast(context.int8_type().pointer(0))
# Identify the function generated by revamb (root)
root_function = module.get_named_function("root")
# Loop over all the generated instructions and add instrumentation code
builder = context.create_builder()
for basic_block in root_function.iter_basic_blocks():
for instruction in basic_block.iter_instructions():
# Check if the current instruction is a call
if instruction.instruction_opcode == llvm.Call:
# The callee is the last operand
last_operand_index = instruction.get_num_operands() - 1
callee = instruction.get_operand(last_operand_index)
# If there's a bitcast, skip it
if not callee.name:
assert(callee.get_num_operands() == 1)
callee = callee.get_operand(0)
# Check if it's performing a syscall
if callee.name.startswith("helper_exception_with_syndrome_"):
# Set the builder's insert point before the call instruction
builder.position_builder_before(instruction)
# Load the value of r7 (which contains the syscall number)
load_r7 = builder.build_load(r7, "")
# Create the list of arguments for dprintf
arguments = [two, message_ptr, load_r7]
# Create the function call to dprintf:
# dprintf(2, "%d\n", r7)
builder.build_call(dprintf, arguments, "")
# Produce the instrumented LLVM IR to file
module.print_module_to_file(sys.argv[2])
if __name__ == "__main__":
main()
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