Doc: update Documentation/exception.txt

Update Documentation/exception.txt.
Remove trailing whitespaces in it.
Signed-off-by: WANG Cong <amwang@redhat.com>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/exception.txt

-     Kernel level exception handling in Linux 2.1.8
+     Kernel level exception handling in Linux
   Commentary by Joerg Pommnitz <joerg@raleigh.ibm.com>
 
 When a process runs in kernel mode, it often has to access user
@@ -29,8 +29,8 @@ page fault handler
 
 void do_page_fault(struct pt_regs *regs, unsigned long error_code)
 
-in arch/i386/mm/fault.c. The parameters on the stack are set up by 
-the low level assembly glue in arch/i386/kernel/entry.S. The parameter
+in arch/x86/mm/fault.c. The parameters on the stack are set up by
+the low level assembly glue in arch/x86/kernel/entry_32.S. The parameter
 regs is a pointer to the saved registers on the stack, error_code
 contains a reason code for the exception.
 
@@ -52,12 +52,12 @@ Where does fixup point to?
 
 Since we jump to the contents of fixup, fixup obviously points
 to executable code. This code is hidden inside the user access macros.
-I have picked the get_user macro defined in include/asm/uaccess.h as an
-example. The definition is somewhat hard to follow, so let's peek at 
+I have picked the get_user macro defined in arch/x86/include/asm/uaccess.h
+as an example. The definition is somewhat hard to follow, so let's peek at
 the code generated by the preprocessor and the compiler. I selected
-the get_user call in drivers/char/console.c for a detailed examination.
+the get_user call in drivers/char/sysrq.c for a detailed examination.
 
-The original code in console.c line 1405:
+The original code in sysrq.c line 587:
         get_user(c, buf);
 
 The preprocessor output (edited to become somewhat readable):