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| -rw-r--r-- | src/supervisor.tex | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/src/supervisor.tex b/src/supervisor.tex index 04104f4..0f03772 100644 --- a/src/supervisor.tex +++ b/src/supervisor.tex @@ -597,6 +597,20 @@ variable-length instructions, {\tt stval} will point to the portion of the instruction that caused the fault while {\tt sepc} will point to the beginning of the instruction. +The {\tt stval} register can optionally also be used to return the +faulting instruction bits on an illegal instruction exception ({\tt + sepc} points to the faulting instruction in memory). + +If this feature is not provided, then {\tt stval} is set to zero on +an illegal instruction fault. + +If the feature is provided, after an illegal instruction trap, {\tt + stval} will contain the entire faulting instruction provided the +instruction is no longer than XLEN bits. If the instruction is less +than XLEN bits long, the upper bits of {\tt stval} are cleared to +zero. If the instruction is more than XLEN bits long, {\tt stval} +will contain the first XLEN bits of the instruction. + \subsection{Supervisor Address Translation and Protection ({\tt satp}) Register} \label{sec:satp} |