X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=doc%2Fuserprog.texi;h=e4e6098b5e8f77acdaf691b967af34d6cc0ef89d;hb=6bfa59ceea7937a705f85de45ba69bf8ba2504c6;hp=7322dd52946c2c9b601063bc717dbd2f38d245cf;hpb=68bad31062d1a3196a9e4d8550d561c22ae5e9cb;p=pintos-anon

diff --git a/doc/userprog.texi b/doc/userprog.texi
index 7322dd5..e4e6098 100644
--- a/doc/userprog.texi
+++ b/doc/userprog.texi
@@ -251,7 +251,8 @@ programs.  The @file{Makefile} in this directory
 compiles the provided examples, and you can edit it
 compile your own programs as well.
 
-Pintos loads @dfn{ELF} executables.  ELF is a file format used by Linux,
+Pintos can load @dfn{ELF} executables with the loader provided for you
+in @file{userprog/process.c}.  ELF is a file format used by Linux,
 Solaris, and many other operating systems for object files,
 shared libraries, and executables.  You can actually use any compiler
 and linker that output 80@var{x}86 ELF executables to produce programs
@@ -481,6 +482,12 @@ The @code{write} system call for writing to fd 1, the system console.
 All of our test programs write to the console (the user process version
 of @func{printf} is implemented this way), so they will all malfunction
 until @code{write} is available.
+
+@item
+For now, change @func{process_wait} to an infinite loop (one that waits
+forever).  The provided implementation returns immediately, so Pintos
+will power off before any processes actually get to run.  You will
+eventually need to provide a correct implementation.
 @end itemize
 
 After the above are implemented, user processes should work minimally.
@@ -593,8 +600,8 @@ the program cannot load or run for any reason.
 @deftypefn {System Call} int wait (pid_t @var{pid})
 Waits for process @var{pid} to die and returns the status it passed to
 @code{exit}.  Returns -1 if @var{pid}
-was terminated by the kernel (i.e.@: killed due to an exception).  If
-@var{pid} is invalid or if it was not a child of the
+was terminated by the kernel (e.g.@: killed due to an exception).  If
+@var{pid} is does not refer to a child of the
 calling thread, or if @code{wait} has already been successfully
 called for the given @var{pid}, returns -1 immediately, without
 waiting.
@@ -659,7 +666,8 @@ Reads @var{size} bytes from the file open as @var{fd} into
 @var{buffer}.  Returns the number of bytes actually read (0 at end of
 file), or -1 if the file could not be read (due to a condition other
 than end of file).  Fd 0 reads from the keyboard using
-@func{kbd_getc}.
+@func{kbd_getc}.  (Keyboard input will not work if you pass the
+@option{-v} option to @command{pintos}.)
 
 Consider implementing this function in terms of @func{file_read}.
 @end deftypefn
@@ -676,7 +684,8 @@ actual number written, or -1 if no bytes could be written at all.
 
 Fd 1 writes to the console.  Your code to write to the console should
 write all of @var{buffer} in one call to @func{putbuf}, at least as
-long as @var{size} is not bigger than a few hundred bytes.  Otherwise,
+long as @var{size} is not bigger than a few hundred bytes.  (It is
+reasonable to break up larger buffers.)  Otherwise,
 lines of text output by different processes may end up interleaved on
 the console, confusing both human readers and our grading scripts.
 
@@ -770,7 +779,8 @@ hurt even now.
 You can use @func{file_deny_write} to prevent writes to an open file.
 Calling @func{file_allow_write} on the file will re-enable them (unless
 the file is denied writes by another opener).  Closing a file will also
-re-enable writes.
+re-enable writes.  Thus, to deny writes to process's executable, you
+must keep it open as long as the process is still running.
 
 @node Project 2 FAQ
 @section FAQ