
Wes Filardo enhanced the riscv/sail-riscv and riscv/riscv-cheri repositories by developing and refining hardware models and security extensions for RISC-V and CHERI architectures. Over four months, Wes introduced type-safe register representations, refactored instruction set encodings, and implemented information flow control mechanisms using Haskell and Sail. Their work included formalizing permission handling, clarifying architectural semantics, and improving documentation to reduce ambiguity and future maintenance risks. By addressing both feature development and bug fixes, Wes improved the robustness and maintainability of system models, demonstrating depth in low-level programming, type system design, and capability security for embedded and formal verification contexts.

Summary for 2025-10: Focused on stabilizing capability permissions in riscv/riscv-cheri by delivering a critical bug fix to YPERMC GL flag clearance and its interaction with Zylevels1. Removed a non-deterministic optional imposition on YPERMC and clarified that CLRPERM can clear the GL flag even when the source capability is sealed. Updated documentation to reflect the clarified semantics and seal interaction. This work preserves compatibility while reducing the risk of permission leakage and edge-case bugs in permission handling.
Summary for 2025-10: Focused on stabilizing capability permissions in riscv/riscv-cheri by delivering a critical bug fix to YPERMC GL flag clearance and its interaction with Zylevels1. Removed a non-deterministic optional imposition on YPERMC and clarified that CLRPERM can clear the GL flag even when the source capability is sealed. Updated documentation to reflect the clarified semantics and seal interaction. This work preserves compatibility while reducing the risk of permission leakage and edge-case bugs in permission handling.
September 2025 monthly summary for riscv/riscv-cheri focusing on architectural correctness, encoding semantics, and maintainability of the SENTRY/JALR/AMB paths. Delivered core refactors and naming updates, introduced ambient sealing types, and expanded cross-references to improve spec clarity. Implemented YSUNSEAL in the base, disentangled SENTRY and JALR, and codified AUIPC shift as a function of encoding. Advanced security modeling groundwork with CT/permission entanglement and mediated sealing workstreams. Completed Xycheriot extension/cap encoding work and related cleanup. Also addressed quality through targeted nit fixes and documentation corrections to reduce future risks.
September 2025 monthly summary for riscv/riscv-cheri focusing on architectural correctness, encoding semantics, and maintainability of the SENTRY/JALR/AMB paths. Delivered core refactors and naming updates, introduced ambient sealing types, and expanded cross-references to improve spec clarity. Implemented YSUNSEAL in the base, disentangled SENTRY and JALR, and codified AUIPC shift as a function of encoding. Advanced security modeling groundwork with CT/permission entanglement and mediated sealing workstreams. Completed Xycheriot extension/cap encoding work and related cleanup. Also addressed quality through targeted nit fixes and documentation corrections to reduce future risks.
August 2025: Expanded platform reach and security model with RV32E/RV64E base ISA support and CHERI enhancements. Delivered ISA-level optimizations, IFC-based security extensions, and versioning for encoding to enable future extensions. Updated documentation, type definitions, and initial system permissions coverage.
August 2025: Expanded platform reach and security model with RV32E/RV64E base ISA support and CHERI enhancements. Delivered ISA-level optimizations, IFC-based security extensions, and versioning for encoding to enable future extensions. Updated documentation, type definitions, and initial system permissions coverage.
Monthly summary for 2024-11: Delivered key type-safety and maintainability improvements to the RISC-V Sail model (riscv/sail-riscv). Implemented a robust newtypes approach for register indices and numbers, extended safety to floating-point and vector registers, and refactored the Zicsr AST for clearer operand representation. These changes reduce runtime errors, improve maintainability, and lay groundwork for safer future extensions in hardware modeling.
Monthly summary for 2024-11: Delivered key type-safety and maintainability improvements to the RISC-V Sail model (riscv/sail-riscv). Implemented a robust newtypes approach for register indices and numbers, extended safety to floating-point and vector registers, and refactored the Zicsr AST for clearer operand representation. These changes reduce runtime errors, improve maintainability, and lay groundwork for safer future extensions in hardware modeling.
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