Trusted Execution Environment(TEE) is a primary means for confidential computing. However, at the moment the RISC-V platform is limited for confidential computing because current RISC-V TEEs either lack scalability or compatibility. The reason for this dilemma in scalability and compatibility is that the standard isolation primitive on RISC-V,Physical Memory Protection(PMP), is not scalable. Meanwhile, previous enclave designs depend on theRich Execution Environment(REE) for OS functionalities, which increases domain switch frequency and enlarges the attack surface of the TEE. In this work, we propose Coffer, a scalable and efficient software-based TEE for the standard RISC-V platform. Coffer includes two core techniques:Logical PMP(LPMP) andEnclave Modules(EModules) to address the issues mentioned above. LPMP is a secure and efficient framework for PMP virtualization. It provides both scalability and hardware compatibility to Coffer. EModules are dynamically assembled lightweight libraries to provide enclaves with OS functionalities. The EModules provide Coffer with software compatibility and reduce theTrusted Computing Base(TCB) size of the enclaves. We implement and evaluate Coffer on commercially available RISC-V devices. The evaluation results show that Coffer can support 2, 000+ concurrent enclaves with negligible performance overhead. Particularly, LPMP supports enclave execution under heavy memory fragmentation with little performance overhead.