X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fuserprog%2Fexception.c;h=8b2e8b641adf7b90168b7b3ff4b3ae81e2bf4d6c;hb=b6e3e1c1e0bd9ccaa88bc4aff36b22b426132ba8;hp=dead766fdbde82b736394f1fc4c8ab92d371ff37;hpb=5fa7a9e2a12522684b0fbaa7d06555544563f124;p=pintos-anon

diff --git a/src/userprog/exception.c b/src/userprog/exception.c
index dead766..8b2e8b6 100644
--- a/src/userprog/exception.c
+++ b/src/userprog/exception.c
@@ -5,6 +5,9 @@
 #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 *);
 
@@ -54,6 +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) 
@@ -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
@@ -113,21 +124,24 @@ kill (struct intr_frame *f)
 static void
 page_fault (struct intr_frame *f) 
 {
-  bool not_present, write, user;
-  uint32_t fault_addr;
-
-  /* Obtain faulting address, then turn interrupts back on.
-     (Interrupts were only off so that we could be assured of
-     reading CR2 before it changed.)
-
-     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. */
+  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).  */
   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;
@@ -136,7 +150,7 @@ page_fault (struct intr_frame *f)
   /* 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. */
-  printf ("Page fault at %08"PRIx32": %s error %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",