Reference to threads/exception.c should be to userprog/exception.c.

[pintos-anon] / doc / vm.texi

diff --git a/doc/vm.texi b/doc/vm.texi
index 3210bbcc83dd021a16f48ad78f7a9284ead20f21..31a8f1ea54a8f3b81131334dcfb53d8e156b2413 100644 (file)
--- a/doc/vm.texi
+++ b/doc/vm.texi
@@ -260,7 +260,7 @@ page fault might only indicate that the page must be brought in from a
 file or swap.  You will have to implement a more sophisticated page
 fault handler to handle these cases.  Your page fault handler, which you
 should implement by modifying @func{page_fault} in
-@file{threads/exception.c}, needs to do roughly the following:
+@file{userprog/exception.c}, needs to do roughly the following:
 
 @enumerate 1
 @item
@@ -590,16 +590,14 @@ user stack pointer.  You will need to arrange another way, such as
 saving @code{esp} into @struct{thread} on the initial transition 
 from user to kernel mode.
 
-You may impose some absolute limit on stack size, as do most OSes.
+You should impose some absolute limit on stack size, as do most OSes.
 Some OSes make the limit user-adjustable, e.g.@: with the
 @command{ulimit} command on many Unix systems.  On many GNU/Linux systems,
 the default limit is 8 MB.
 
-The first stack page need not be allocated lazily.  You can initialize
-it with the command line arguments at load time, with no need to wait
-for it to be faulted in.  (Even if you did wait, the very first
-instruction in the user program is likely to be one that faults in the
-page.)
+The first stack page need not be allocated lazily.  You can allocate
+and initialize it with the command line arguments at load time, with 
+no need to wait for it to be faulted in.
 
 All stack pages should be candidates for eviction.  An evicted stack
 page should be written to swap.
@@ -716,6 +714,12 @@ process.  If you carefully designed your data structures,
 sharing of read-only pages should not make this part significantly
 harder.
 
+@item How do we resume a process after we have handled a page fault?
+
+Returning from @func{page_fault} resumes the current user process
+(@pxref{Internal Interrupt Handling}).
+It will then retry the instruction to which the instruction pointer points.
+
 @item Does the virtual memory system need to support data segment growth?
 
 No.  The size of the data segment is determined by the linker.  We still