Add additional disclaimer to "diffstat"s.

[pintos-anon] / doc / vm.texi

diff --git a/doc/vm.texi b/doc/vm.texi
index 6f0c1a71b2e60b7cdeff0b8339580449426edb41..8ea6ee46b8c37b6897df3ddd365ed9428c731d1e 100644 (file)
--- a/doc/vm.texi
+++ b/doc/vm.texi
@@ -213,6 +213,9 @@ could check and update the accessed and dirty bits for both addresses.
 Alternatively, the kernel could avoid the problem by only accessing user
 data through the user virtual address.
 
+Other aliases should only arise if you implement sharing, as extra
+credit (@pxref{VM Extra Credit}), or as bugs elsewhere in your code.
+
 @deftypefun bool pagedir_is_dirty (uint32_t *@var{pd}, const void *@var{vpage})
 @deftypefunx bool pagedir_is_accessed (uint32_t *@var{pd}, const void *@var{vpage})
 Returns true if page directory @var{pd} contains a page table entry for
@@ -476,7 +479,7 @@ script, so the code you turn in must properly handle all cases.
 Implement stack growth.  In project 2, the stack was a single page at
 the top of the user virtual address space, and programs were limited to
 that much stack.  Now, if the stack grows past its current size,
-allocate additional page as necessary.
+allocate additional pages as necessary.
 
 Allocate additional pages only if they ``appear'' to be stack accesses.
 Devise a heuristic that attempts to distinguish stack accesses from
@@ -577,9 +580,15 @@ Here's a summary of our reference solution, produced by the
 @command{diffstat} program.  The final row gives total lines inserted
 and deleted; a changed line counts as both an insertion and a deletion.
 
-This summary is relative to the Pintos base code, but we started from
-the reference solution to project 2.  @xref{Project 2 FAQ}, for the
-summary of project 2.
+This summary is relative to the Pintos base code, but the reference
+solution for project 3 starts from the reference solution to project 2.
+@xref{Project 2 FAQ}, for the summary of project 2.
+
+The reference solution represents just one possible solution.  Many
+other solutions are also possible and many of those differ greatly from
+the reference solution.  Some excellent solutions may not modify all the
+files modified by the reference solution, and some may modify files not
+modified by the reference solution.
 
 @verbatim
  Makefile.build       |    4 
@@ -607,6 +616,7 @@ summary of project 2.
 Yes.
 
 @item What extra credit is available?
+@anchor{VM Extra Credit}
 
 You may implement sharing: when multiple processes are created that use
 the same executable file, share read-only pages among those processes