From 285c81746fe664060b62ae0584865dbfa9f42e1a Mon Sep 17 00:00:00 2001 From: Jacob Bachmeyer Date: Mon, 15 May 2017 22:12:00 -0500 Subject: Forbid S-mode execution from user memory --- src/machine.tex | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'src/machine.tex') diff --git a/src/machine.tex b/src/machine.tex index d92aa58..169956a 100644 --- a/src/machine.tex +++ b/src/machine.tex @@ -634,7 +634,7 @@ machine mode. \end{commentary} The SUM (permit Supervisor User Memory access) bit modifies the privilege with -which S-mode loads, stores, and instruction fetches access virtual memory. +which S-mode loads and stores access virtual memory. When SUM=0, S-mode memory accesses to pages that are accessible by U-mode (U=1 in Figure~\ref{sv32pte}) will fault. When SUM=1, these accesses are permitted. SUM has no effect when page-based virtual memory is not in effect. -- cgit v1.1