Clarifications.

[pintos-anon] / doc / userprog.texi

diff --git a/doc/userprog.texi b/doc/userprog.texi
index bab70ec7c178094f1e1ef581b8dc18648c761acc..92959ec06f9e1242328e59688bbf5992099bb314 100644 (file)
--- a/doc/userprog.texi
+++ b/doc/userprog.texi
@@ -415,7 +415,7 @@ provide a little bit of helpful code:
    Returns true if successful, false if USRC is invalid. */
 static inline bool get_user (uint8_t *kdst, const uint8_t *usrc) {
   int eax;
-  asm ("mov %%eax, offset 1f; mov %%al, %2; mov %0, %%al; 1:"
+  asm ("movl $1f, %%eax; movb %2, %%al; movb %%al, %0; 1:"
        : "=m" (*kdst), "=&a" (eax) : "m" (*usrc));
   return eax != 0;
 }
@@ -424,7 +424,7 @@ static inline bool get_user (uint8_t *kdst, const uint8_t *usrc) {
    Returns true if successful, false if UDST is invalid. */
 static inline bool put_user (uint8_t *udst, uint8_t byte) {
   int eax;
-  asm ("mov %%eax, offset 1f; mov %0, %b2; 1:"
+  asm ("movl $1f, %%eax; movb %b2, %0; 1:"
        : "=m" (*udst), "=&a" (eax) : "r" (byte));
   return eax != 0;
 }
@@ -638,15 +638,15 @@ The file defines other syscalls.  Ignore them for now.  You will
 implement some of them in project 3 and the rest in project 4, so be
 sure to design your system with extensibility in mind.
 
-To implement syscalls, you need to provide ways to copy data
-from user virtual address space into the kernel and vice versa.
+To implement syscalls, you need to provide ways to read and write data
+in user virtual address space.
 You need this ability before you can
 even obtain the system call number, because the system call number is
 on the user's stack in the user's virtual address space.
 This can be a bit tricky: what if the user provides an invalid
 pointer, a pointer into kernel memory, or a block
 partially in one of those regions?  You should handle these cases by
-terminating the user process.    We recommend
+terminating the user process.  We recommend
 writing and testing this code before implementing any other system
 call functionality.
 
@@ -783,6 +783,10 @@ user program C library does not have a @func{malloc} implementation.
 
 Modify @file{src/examples/Makefile}, then run @command{make}.
 
+@item Can I run user programs under a debugger?
+
+Yes, with some limitations.  @xref{Debugging User Programs}.
+
 @item What's the difference between @code{tid_t} and @code{pid_t}?
 
 A @code{tid_t} identifies a kernel thread, which may have a user