diff options
author | Andrew Waterman <andrew@sifive.com> | 2017-11-09 16:28:38 -0800 |
---|---|---|
committer | Andrew Waterman <andrew@sifive.com> | 2017-11-09 16:54:55 -0800 |
commit | 0b7756c337891ea2af90fc9a124917a3696f7a6a (patch) | |
tree | 1cb76e671ccd0d32a37ec2cc6d8a5b78b00520cf | |
parent | 6a92b89bdf7d8d83b6e4a828658628c991aeab50 (diff) | |
download | riscv-isa-manual-0b7756c337891ea2af90fc9a124917a3696f7a6a.zip riscv-isa-manual-0b7756c337891ea2af90fc9a124917a3696f7a6a.tar.gz riscv-isa-manual-0b7756c337891ea2af90fc9a124917a3696f7a6a.tar.bz2 |
Specify meaning of R/W/X bits in PTE
-rw-r--r-- | src/supervisor.tex | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/src/supervisor.tex b/src/supervisor.tex index d10cf0a..3bd0c8b 100644 --- a/src/supervisor.tex +++ b/src/supervisor.tex @@ -1119,6 +1119,19 @@ X & W & R & Meaning \\ \label{pteperm} \end{table*} +Attempting to fetch an instruction from a page that does not have execute +permissions raises a fetch page-fault exception. Attempting to execute +a load or load-reserved instruction whose effective address lies within +a page without read permissions raises a load page-fault exception. +Attempting to execute a store, store-conditional (regardless of success), +or AMO instruction whose effective address lies within a page without +write permissions raises a store page-fault exception. +\begin{commentary} +AMOs never raise load page-fault exceptions. Since any unreadable page is +also unwritable, attempting to perform an AMO on an unreadable page always +raises a store page-fault exception. +\end{commentary} + The U bit indicates whether the page is accessible to user mode. U-mode software may only access the page when U=1. If the SUM bit in the {\tt sstatus} register is |