An LLDB plugin to render blocks of pixels from memory

lldb_showimg.py

import lldb
import matplotlib.pyplot as plt
import numpy as np


def __lldb_init_module(debugger, internal_dict):
    debugger.HandleCommand("command script add -f lldb_showimg.showimg showimg")


def _pop_arg(args):
    arg = args.pop(0)
    if arg.startswith('"'):
        while not arg.endswith('"'):
            arg += " " + args.pop(0)
        arg = arg[1:-1]
    return arg


# @TODO: Replace with ParsedCommand when this is in an LLVM release
def _parse_args(args):
    args = args.split()
    base = _pop_arg(args)
    stride = _pop_arg(args)
    width = _pop_arg(args)
    height = _pop_arg(args)
    bitdepth = _pop_arg(args)
    return base, stride, width, height, bitdepth


def showimg(debugger, command, exe_ctx, result, internal_dict):
    frame = exe_ctx.GetFrame()
    target = debugger.GetSelectedTarget()
    process = target.GetProcess()

    base, stride, width, height, bitdepth = _parse_args(command)
    base = frame.EvaluateExpression(base).unsigned
    # @TODO: Use GetValueAsAddress if available
    base = base.GetValueAsUnsigned()
    stride = frame.EvaluateExpression(stride).signed
    width = frame.EvaluateExpression(width).unsigned
    height = frame.EvaluateExpression(height).unsigned
    bitdepth = frame.EvaluateExpression(bitdepth).unsigned
    sample_size = (bitdepth + 7) // 8

    array = np.empty((height, width))
    for y in range(height):
        for x in range(width):
            addr = base + y * stride + x * sample_size
            error_ref = lldb.SBError()
            sample = process.ReadMemory(addr, sample_size, error_ref)
            sample = int.from_bytes(sample, byteorder="little")
            array[y][x] = sample

    plt.imshow(array, cmap="gray", vmin=0, vmax=1 << bitdepth)
    plt.show()