X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=doc%2Fuserprog.texi;h=8524219bf0acc5052f5d75e52817fd4999b2bb79;hb=549e11aeae62a517eb513c6dc1e3e267b8293781;hp=a9a84b2dcd854609cbd40bd82648cf96b1a9773c;hpb=f415a37905c57f61b444806bf84f5405184452aa;p=pintos-anon

diff --git a/doc/userprog.texi b/doc/userprog.texi
index a9a84b2..8524219 100644
--- a/doc/userprog.texi
+++ b/doc/userprog.texi
@@ -20,10 +20,7 @@ assignment.  The ``alarm clock'' functionality may be useful in
 projects 3 and 4, but it is not strictly required.
 
 You might find it useful to go back and reread how to run the tests
-(@pxref{Testing}).  In particular, the tests for project 2 and later
-projects will probably run faster if you use the qemu emulator, e.g.@:
-via @code{make check PINTOSOPTS='--qemu'}.  The qemu emulator is
-available only on the Linux machines.
+(@pxref{Testing}).
 
 @menu
 * Project 2 Background::        
@@ -304,7 +301,7 @@ 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_BASE} accesses physical
-address 0, virtual address @code{PHYS_BASE} + @t{0x1234} access
+address 0, virtual address @code{PHYS_BASE} + @t{0x1234} accesses
 physical address @t{0x1234}, and so on up to the size of the machine's
 physical memory.
 
@@ -317,11 +314,6 @@ the running process.  However, even in the kernel, an attempt to
 access memory at an unmapped user virtual address
 will cause a page fault.
 
-You must handle memory fragmentation gracefully, that is, a process that
-needs @var{N} pages of user virtual memory must not require those pages
-to be contiguous in physical memory (or, equivalently, in kernel virtual
-memory).
-
 @menu
 * Typical Memory Layout::       
 @end menu
@@ -430,29 +422,37 @@ Therefore, for those who want to try the latter technique, we'll
 provide a little bit of helpful code:
 
 @verbatim
-/* Tries to copy a byte from user address USRC to kernel address KDST.
-   Returns true if successful, false if USRC is invalid. */
-static inline bool get_user (uint8_t *kdst, const uint8_t *usrc) {
-  int eax;
-  asm ("movl $1f, %%eax; movb %2, %%al; movb %%al, %0; 1:"
-       : "=m" (*kdst), "=&a" (eax) : "m" (*usrc));
-  return eax != 0;
+/* Reads a byte at user virtual address UADDR.
+   UADDR must be below PHYS_BASE.
+   Returns the byte value if successful, -1 if a segfault
+   occurred. */
+static int
+get_user (const uint8_t *uaddr)
+{
+  int result;
+  asm ("movl $1f, %0; movzbl %1, %0; 1:"
+       : "=&a" (result) : "m" (*uaddr));
+  return result;
 }
-
-/* Tries to write BYTE to user address UDST.
-   Returns true if successful, false if UDST is invalid. */
-static inline bool put_user (uint8_t *udst, uint8_t byte) {
-  int eax;
-  asm ("movl $1f, %%eax; movb %b2, %0; 1:"
-       : "=m" (*udst), "=&a" (eax) : "r" (byte));
-  return eax != 0;
+ 
+/* Writes BYTE to user address UDST.
+   UDST must be below PHYS_BASE.
+   Returns true if successful, false if a segfault occurred. */
+static bool
+put_user (uint8_t *udst, uint8_t byte)
+{
+  int error_code;
+  asm ("movl $1f, %0; movb %b2, %1; 1:"
+       : "=&a" (error_code), "=m" (*udst) : "r" (byte));
+  return error_code != -1;
 }
 @end verbatim
 
 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 merely sets
-@code{eax} to 0 and copies its former value into @code{eip}.
+modified @func{page_fault} so that a page fault in the kernel merely
+sets @code{eax} to @t{0xffffffff} and copies its former value
+into @code{eip}.
 
 @node Project 2 Suggested Order of Implementation
 @section Suggested Order of Implementation
@@ -566,13 +566,13 @@ word is the program name, the second word is the first argument, and so
 on.  That is, @code{process_execute("grep foo bar")} should run
 @command{grep} passing two arguments @code{foo} and @code{bar}.
 
-Within a command line, multiple spaces are equivalent to a single space,
-so that @code{process_execute("grep foo bar")} is equivalent to our
-original example.  You can impose a reasonable limit on the length of
-the command line arguments.  For example, you could limit the arguments
-to those that will fit in a single page (4 kB).  (There is an unrelated
-limit of 128 bytes on command-line arguments that the @command{pintos}
-utility can pass to the kernel.)
+Within a command line, multiple spaces are equivalent to a single
+space, so that @code{process_execute("grep @w{ }foo @w{ }@w{ }bar")}
+is equivalent to our original example.  You can impose a reasonable
+limit on the length of the command line arguments.  For example, you
+could limit the arguments to those that will fit in a single page (4
+kB).  (There is an unrelated limit of 128 bytes on command-line
+arguments that the @command{pintos} utility can pass to the kernel.)
 
 You can parse argument strings any way you like.  If you're lost,
 look at @func{strtok_r}, prototyped in @file{lib/string.h} and
@@ -619,10 +619,11 @@ the program cannot load or run for any reason.
 @end deftypefn
 
 @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}
+If process @var{pid} is still alive, waits until it dies.
+Then, returns the status that @var{pid} passed to @code{exit},
+or -1 if @var{pid}
 was terminated by the kernel (e.g.@: killed due to an exception).  If
-@var{pid} is does not refer to a child of the
+@var{pid} 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.
@@ -674,6 +675,12 @@ as explicitly described below.
 
 Each process has an independent set of file descriptors.  File
 descriptors are not inherited by child processes.
+
+When a single file is opened more than once, whether by a single
+process or different processes, each @code{open} returns a new file
+descriptor.  Different file descriptors for a single file are closed
+independently in separate calls to @code{close} and they do not share
+a file position.
 @end deftypefn
 
 @deftypefn {System Call} int filesize (int @var{fd})
@@ -685,8 +692,7 @@ 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}.  (Keyboard input will not work if you pass the
-@option{-v} option to @command{pintos}.)
+@func{input_getc}.
 @end deftypefn
 
 @deftypefn {System Call} int write (int @var{fd}, const void *@var{buffer}, unsigned @var{size})
@@ -905,12 +911,6 @@ You can choose whatever suitable types you like for @code{tid_t} and
 @code{pid_t}.  By default, they're both @code{int}.  You can make them
 a one-to-one mapping, so that the same values in both identify the
 same process, or you can use a more complex mapping.  It's up to you.
-
-@item Keyboard input doesn't work.
-
-You are probably passing @option{-v} to @command{pintos}, but
-serial input isn't implemented.  Don't use @option{-v} if you
-want to use the shell or otherwise need keyboard input.
 @end table
 
 @menu