Static binary code analysis and reverse engineering are crucial operations for malware analysis, binary-level software protections, debugging, and patching, among many other tasks. Faster binary code analysis tools are necessary for tasks such as analyzing the multitude of new malware samples gathered every day. Binary code disassembly is a core functionality of such tools which has not received enough attention from a performance perspective. In this paper we introduce GPUDisasm, a GPU-based disassembly framework for x86 code that takes advantage of graphics processors to achieve efficient large-scale analysis of binary executables. We describe in detail various optimizations and design decisions for achieving both inter-parallelism, to disassemble multiple binaries in parallel, as well as intra-parallelism, to decode multiple instructions of the same binary in parallel. The results of our experimental evaluation in terms of performance and power consumption demonstrate that GPU-Disasm is twice as fast than a CPU disassembler for linear disassembly and 4.4 times faster for exhaustive disassembly, with power consumption comparable to CPU-only implementations.