Clarify how termination treats file descriptors.

[pintos-anon] / doc / userprog.texi

diff --git a/doc/userprog.texi b/doc/userprog.texi
index b7d356ff0790b13b639ea1072429decc78e324dc..59186129ca02ce05234a58f1f62f34dba5f081c6 100644 (file)
--- a/doc/userprog.texi
+++ b/doc/userprog.texi
@@ -295,8 +295,8 @@ Kernel virtual memory is global.  It is always mapped the same way,
 regardless of what user process or kernel thread is running.  In
 Pintos, kernel virtual memory is mapped one-to-one to physical
 memory, starting at @code{PHYS_BASE}.  That is, virtual address
 regardless of what user process or kernel thread is running.  In
 Pintos, kernel virtual memory is mapped one-to-one to physical
 memory, starting at @code{PHYS_BASE}.  That is, virtual address

-@code{PHYS_ADDR} accesses physical
-address 0, virtual address @code{PHYS_ADDR} + @t{0x1234} access
+@code{PHYS_BASE} accesses physical
+address 0, virtual address @code{PHYS_BASE} + @t{0x1234} access

 physical address @t{0x1234}, and so on up to the size of the machine's
 physical memory.
 
 physical address @t{0x1234}, and so on up to the size of the machine's
 physical memory.
 


@@ -442,8 +442,8 @@ static inline bool put_user (uint8_t *udst, uint8_t byte) {
 
 Each of these functions assumes that the user address has already been
 verified to be below @code{PHYS_BASE}.  They also assume that you've
 
 Each of these functions assumes that the user address has already been
 verified to be below @code{PHYS_BASE}.  They also assume that you've

-modified @func{page_fault} so that a page fault in the kernel causes
-@code{eax} to be set to 0 and its former value copied into @code{eip}.
+modified @func{page_fault} so that a page fault in the kernel merely sets
+@code{eax} to 0 and copies its former value into @code{eip}.

 
 @node Project 2 Suggested Order of Implementation
 @section Suggested Order of Implementation
 
 @node Project 2 Suggested Order of Implementation
 @section Suggested Order of Implementation


@@ -453,7 +453,7 @@ parallel:
 
 @itemize
 @item
 
 @itemize
 @item

-Argument passing (@pxref{Argument Passing}).  Every user programs will
+Argument passing (@pxref{Argument Passing}).  Every user program will

 page fault immediately until argument passing is implemented.
 
 For now, you may simply wish to change
 page fault immediately until argument passing is implemented.
 
 For now, you may simply wish to change


@@ -468,6 +468,11 @@ in @func{setup_stack}.  That will work for any test program that doesn't
 examine its arguments, although its name will be printed as
 @code{(null)}.
 
 examine its arguments, although its name will be printed as
 @code{(null)}.
 

+Until you implement argument passing, you should only run programs
+without passing command-line arguments.  Attempting to pass arguments to
+a program will include those arguments in the name of the program, which
+will probably fail.
+

 @item
 User memory access (@pxref{Accessing User Memory}).  All system calls
 need to read user memory.  Few system calls need to write to user
 @item
 User memory access (@pxref{Accessing User Memory}).  All system calls
 need to read user memory.  Few system calls need to write to user


@@ -651,13 +656,16 @@ Consider implementing this function in terms of @func{filesys_remove}.
 @deftypefn {System Call} int open (const char *@var{file})
 Opens the file called @var{file}.  Returns a nonnegative integer handle
 called a ``file descriptor'' (fd), or -1 if the file could not be
 @deftypefn {System Call} int open (const char *@var{file})
 Opens the file called @var{file}.  Returns a nonnegative integer handle
 called a ``file descriptor'' (fd), or -1 if the file could not be

-opened.  All open files associated with a process should be closed
-when the process exits or is terminated.
+opened.  

 
 File descriptors numbered 0 and 1 are reserved for the console: fd 0
 is standard input (@code{stdin}), fd 1 is standard output
 
 File descriptors numbered 0 and 1 are reserved for the console: fd 0
 is standard input (@code{stdin}), fd 1 is standard output

-(@code{stdout}).  These special file descriptors are valid as system
-call arguments only as explicitly described below.
+(@code{stdout}).  The @code{open} system call will never return either
+of these file descriptors, which are valid as system call arguments only
+as explicitly described below.
+
+Each process has an independent set of file descriptors.  File
+descriptors are not inherited by child processes.

 
 Consider implementing this function in terms of @func{filesys_open}.
 @end deftypefn
 
 Consider implementing this function in terms of @func{filesys_open}.
 @end deftypefn


@@ -723,7 +731,9 @@ Consider implementing this function in terms of @func{file_tell}.
 @end deftypefn
 
 @deftypefn {System Call} void close (int @var{fd})
 @end deftypefn
 
 @deftypefn {System Call} void close (int @var{fd})

-Closes file descriptor @var{fd}.
+Closes file descriptor @var{fd}.  
+Exiting or terminating a process implicitly closes all its open file
+descriptors, as if by calling this function for each one.

 
 Consider implementing this function in terms of @func{file_close}.
 @end deftypefn
 
 Consider implementing this function in terms of @func{file_close}.
 @end deftypefn


@@ -799,6 +809,12 @@ 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.
 
 @command{diffstat} program.  The final row gives total lines inserted
 and deleted; a changed line counts as both an insertion and a deletion.
 

+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
  threads/thread.c     |   13 
  threads/thread.h     |   26 +
 @verbatim
  threads/thread.c     |   13 
  threads/thread.h     |   26 +