AT_HWCAP is a field in the elf auxiliary vector meant to describe cpu-specific hardware features. For RISC-V we want to use this to indicate the presence of any standard extensions supported by the CPU. This allows userland applications to query the system for supported extensions using elf_aux_info(3). Support for an extension is indicated by the presence of its corresponding bit in AT_HWCAP -- e.g. systems supporting the 'c' extension (compressed instructions) will have the second bit set. Extensions advertised through AT_HWCAP are only those that are supported by all harts in the system. Reviewed by: jhb, markj Approved by: markj (mentor) MFC after: 2 weeks Differential Revision: https://reviews.freebsd.org/D20493 |
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