X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=doc%2Fuserprog.texi;h=b50dc364829edcc186491b875e68e1b4cd470a72;hb=51352183b5bd8c3671c24d927f5c69ab7ea04e83;hp=fa534d2382ef3007c36a3f809efbe3eaee29be55;hpb=837e5b7fb902bd749106309ef76a5276c73ca34c;p=pintos-anon

diff --git a/doc/userprog.texi b/doc/userprog.texi
index fa534d2..b50dc36 100644
--- a/doc/userprog.texi
+++ b/doc/userprog.texi
@@ -301,7 +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.
 
@@ -314,11 +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
@@ -571,13 +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
@@ -679,6 +674,12 @@ 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})