Comments.

[pintos-anon] / src / userprog / exception.c

diff --git a/src/userprog/exception.c b/src/userprog/exception.c
index 79ba7a921b61042e111cce1b0c6231f7ed1cc8ea..745adaa086e4614245748ddd3cbc6c6262b1f5de 100644 (file)
--- a/src/userprog/exception.c
+++ b/src/userprog/exception.c
@@ -1,9 +1,12 @@
-#include "exception.h"
+#include "userprog/exception.h"
 #include <inttypes.h>
-#include "lib.h"
-#include "gdt.h"
-#include "interrupt.h"
-#include "thread.h"
+#include <stdio.h>
+#include "userprog/gdt.h"
+#include "threads/interrupt.h"
+#include "threads/thread.h"
+
+/* Number of page faults processed. */
+static long long page_fault_cnt;
 
 static void kill (struct intr_frame *);
 static void page_fault (struct intr_frame *);
@@ -12,9 +15,10 @@ static void page_fault (struct intr_frame *);
    programs.
 
    In a real Unix-like OS, most of these interrupts would be
-   passed along to the user process in the form of signals, but
-   we don't implement signals.  Instead, we'll make them simply
-   kill the user process.
+   passed along to the user process in the form of signals, as
+   described in [SV-386] 3-24 and 3-25, but we don't implement
+   signals.  Instead, we'll make them simply kill the user
+   process.
 
    Page faults are an exception.  Here they are treated the same
    way as other exceptions, but this will need to change to
@@ -53,6 +57,13 @@ exception_init (void)
   intr_register (14, 0, INTR_OFF, page_fault, "#PF Page-Fault Exception");
 }
 
+/* Prints exception statistics. */
+void
+exception_print_stats (void) 
+{
+  printf ("Exception: %lld page faults\n", page_fault_cnt);
+}
+
 /* Handler for an exception (probably) caused by a user process. */
 static void
 kill (struct intr_frame *f) 
@@ -72,9 +83,8 @@ kill (struct intr_frame *f)
     case SEL_UCSEG:
       /* User's code segment, so it's a user exception, as we
          expected.  Kill the user process.  */
-      printk ("%s: dying due to interrupt %#04x (%s).\n",
-              thread_name (thread_current ()),
-              f->vec_no, intr_name (f->vec_no));
+      printf ("%s: dying due to interrupt %#04x (%s).\n",
+              thread_name (), f->vec_no, intr_name (f->vec_no));
       intr_dump_frame (f);
       thread_exit (); 
 
@@ -89,7 +99,7 @@ kill (struct intr_frame *f)
     default:
       /* Some other code segment?  Shouldn't happen.  Panic the
          kernel. */
-      printk ("Interrupt %#04x (%s) in unknown segment %04x\n",
+      printf ("Interrupt %#04x (%s) in unknown segment %04x\n",
              f->vec_no, intr_name (f->vec_no), f->cs);
       thread_exit ();
     }
@@ -101,7 +111,8 @@ kill (struct intr_frame *f)
 #define PF_U 0x4    /* 0: kernel, 1: user process. */
 
 /* Page fault handler.  This is a skeleton that must be filled in
-   to implement virtual memory.
+   to implement virtual memory.  Some solutions to project 2 may
+   also require modifying this code.
 
    At entry, the address that faulted is in CR2 (Control Register
    2) and information about the fault, formatted as described in
@@ -113,27 +124,36 @@ kill (struct intr_frame *f)
 static void
 page_fault (struct intr_frame *f) 
 {
-  bool not_present, write, user;
-  uint32_t fault_addr;
+  bool not_present;  /* True: not-present page, false: writing r/o page. */
+  bool write;        /* True: access was write, false: access was read. */
+  bool user;         /* True: access by user, false: access by kernel. */
+  void *fault_addr;  /* Fault address. */
+
+  /* Obtain faulting address, the virtual address that was
+     accessed to cause the fault.  It may point to code or to
+     data.  It is not necessarily the address of the instruction
+     that caused the fault (that's f->eip).
+     See [IA32-v2a] "MOV--Move to/from Control Registers" and
+     [IA32-v3] 5.14 "Interrupt 14--Page Fault Exception
+     (#PF)". */
+  asm ("movl %%cr2, %0" : "=r" (fault_addr));
+
+  /* Turn interrupts back on (they were only off so that we could
+     be assured of reading CR2 before it changed). */
+  intr_enable ();
+
+  /* Count page faults. */
+  page_fault_cnt++;
 
   /* Determine cause. */
   not_present = (f->error_code & PF_P) == 0;
   write = (f->error_code & PF_W) != 0;
   user = (f->error_code & PF_U) != 0;
 
-  /* Obtain faulting address.
-
-     (The faulting address is not necesarily the address of the
-     instruction that caused the fault--that's in F's eip
-     member.  Rather, it's the linear address that was accessed
-     to cause the fault, which is probably an address of data,
-     not code.) */
-  asm ("movl %%cr2, %0" : "=r" (fault_addr));
-
   /* To implement virtual memory, delete the rest of the function
      body, and replace it with code that brings in the page to
      which fault_addr refers. */
-  printk ("Page fault on address %08"PRIx32": %s %s page in %s context.\n",
+  printf ("Page fault at %p: %s error %s page in %s context.\n",
           fault_addr,
           not_present ? "not present" : "rights violation",
           write ? "writing" : "reading",