凿壁偷光

lit. to collect fireflies and study by their light (idiom); fig. ambitious student from impoverished background; burning the midnight oil

to study assiduously and tirelessly (idiom); see also 头悬梁，锥刺股

lit. with his head attached to a beam and stabbing his thigh with an awl (idiom); fig. to study assiduously and tirelessly

lit. always with a book in hand (idiom); fig. (of a student or scholar) diligent and hardworking

lit. to hang one's books on cow horns (idiom); fig. to be diligent in one's studies

to grind one's way through an ink stone; to persevere in a difficult task (idiom)