-#include "exception.h"
-#include "lib.h"
-#include "gdt.h"
-#include "interrupt.h"
-#include "thread.h"
+#include "userprog/exception.h"
+#include <inttypes.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 *);
/* Registers handlers for interrupts that can be caused by user
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
/* Most exceptions can be handled with interrupts turned on.
We need to disable interrupts for page faults because the
fault address is stored in CR2 and needs to be preserved. */
- intr_register (14, 0, INTR_OFF, kill, "#PF Page-Fault Exception");
+ 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. */
{
case SEL_UCSEG:
/* User's code segment, so it's a user exception, as we
- expected. */
- printk ("%s: dying due to interrupt %#04x (%s).\n",
- thread_name (thread_current ()),
- f->vec_no, intr_name (f->vec_no));
+ expected. Kill the user process. */
+ 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 ();
/* Kernel's code segment, which indicates a kernel bug.
Kernel code shouldn't throw exceptions. (Page faults
may cause kernel exceptions--but they shouldn't arrive
- here.) */
+ here.) Panic the kernel to make the point. */
intr_dump_frame (f);
PANIC ("Kernel bug - unexpected interrupt in kernel");
default:
- /* Some other code segment? Shouldn't happen. */
- printk ("Interrupt %#04x (%s) in unknown segment %04x\n",
+ /* Some other code segment? Shouldn't happen. Panic the
+ kernel. */
+ printf ("Interrupt %#04x (%s) in unknown segment %04x\n",
f->vec_no, intr_name (f->vec_no), f->cs);
thread_exit ();
}
}
+/* Page fault error code bits that describe the cause of the exception. */
+#define PF_P 0x1 /* 0: not-present page. 1: access rights violation. */
+#define PF_W 0x2 /* 0: read, 1: write. */
+#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. 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
+ the PF_* macros above, is in F's error_code member. The
+ example code here shows how to parse that information. You
+ can find more information about both of these in the
+ description of "Interrupt 14--Page Fault Exception (#PF)" in
+ [IA32-v3] section 5.14, which is pages 5-46 to 5-49. */
+static void
+page_fault (struct intr_frame *f)
+{
+ 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;
+
+ /* 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 %p: %s error %s page in %s context.\n",
+ fault_addr,
+ not_present ? "not present" : "rights violation",
+ write ? "writing" : "reading",
+ user ? "user" : "kernel");
+ kill (f);
+}
+
projects / pintos-anon / blobdiff