X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=doc%2Fuserprog.texi;h=78ef78d8bfc8d9ba3e41a5b67407f7a1390e01e7;hb=c37b82251bbe85edf2d46284f6d4b43b92b09182;hp=f70957f6617ba4a39f32b6a9f7129adb0214d620;hpb=e5a71e1b767082687454f54f3c72b53665101d74;p=pintos-anon

diff --git a/doc/userprog.texi b/doc/userprog.texi
index f70957f..78ef78d 100644
--- a/doc/userprog.texi
+++ b/doc/userprog.texi
@@ -247,14 +247,21 @@ requirements:
 
 @itemize @bullet
 @item
-The kernel should print out the program's name and exit status
-whenever a process terminates, e.g.@: @code{shell: exit(-1)}, whether
-termination is due to a call to the @code{exit} system call or for
-another reason.  The name printed should be the full name passed to
-@func{process_execute}, except that it is acceptable to truncate it to
-15 characters to allow for the limited space in @struct{thread}.
+The kernel should print out the program's name and exit status whenever
+a process terminates, whether termination is caused by the @code{exit}
+system call or for another reason.
 
 @itemize @minus
+@item
+The message must be formatted exactly as if it was printed with
+@code{printf ("%s: exit(%d)\n", @dots{});} given appropriate arguments.
+
+@item
+The name printed should be the full name passed to
+@func{process_execute}, except that it is acceptable to truncate it to
+15 characters to allow for the limited space in @struct{thread}.  The
+name printed need not include arguments.
+
 @item
 Do not print a message when a kernel thread that is not a process
 terminates.
@@ -264,7 +271,7 @@ Do not print messages about process termination for the @code{halt}
 system call.
 
 @item
-No message need be printed when a process that fails to load.
+No message need be printed when a process fails to load.
 @end itemize
 
 @item
@@ -459,7 +466,7 @@ the @file{filesys} directory, and release it afterward.  Don't forget
 that @func{process_execute} also accesses files.  @strong{For now, we
 recommend against modifying code in the @file{filesys} directory.}
 
-We have provided you a function for each system call in
+We have provided you a user-level function for each system call in
 @file{lib/user/syscall.c}.  These provide a way for user processes to
 invoke each system call from a C program.  Each of them calls an
 assembly language routine in @file{lib/user/syscall-stub.S}, which in
@@ -467,8 +474,11 @@ turn invokes the system call interrupt and returns.
 
 When you're done with this part, and forevermore, Pintos should be
 bulletproof.  Nothing that a user program can do should ever cause the
-OS to crash, halt, assert fail, or otherwise stop running.  The sole
-exception is a call to the @code{halt} system call.
+OS to crash, halt, assert fail, or otherwise stop running.  It is
+important to emphasize this point: our tests will try to break your
+system calls in many, many ways.  You need to think of all the corner
+cases and handle them.  The sole way a user program should be able to
+cause the OS to halt is by invoking the @code{halt} system call.
 
 If a system call is passed an invalid argument, acceptable options
 include returning an error value (for those calls that return a
@@ -832,7 +842,7 @@ After we push all of the strings onto the stack, we adjust the stack
 pointer so that it is word-aligned: that is, we move it down to the
 next 4-byte boundary.  This is required because we will next be
 placing several words of data on the stack, and they must be aligned
-in order to be read correctly.  In our example, as you'll see below,
+to be read correctly.  In our example, as you'll see below,
 the strings start at address @t{0xffed}.  One word below that would be
 at @t{0xffe9}, so we could in theory put the next word on the stack
 there.  However, since the stack pointer should always be
@@ -964,3 +974,9 @@ In this example, the caller's stack pointer would be at
 The 80@var{x}86 convention for function return values is to place them
 in the @samp{EAX} register.  System calls that return a value can do
 so by modifying the @samp{eax} member of @struct{intr_frame}.
+
+You should try to avoid writing large amounts of repetitive code for
+implementing system calls.  Each system call argument, whether an
+integer or a pointer, takes up 4 bytes on the stack.  You should be able
+to take advantage of this to avoid writing much near-identical code for
+retrieving each system call's arguments from the stack.