Comments.

[pintos-anon] / src / threads / interrupt.c

diff --git a/src/threads/interrupt.c b/src/threads/interrupt.c
index 8173ec11dcc44767c7cd5d02158651e48433eab4..c6ca2bd0060339b19aa38d92655564a4869878e1 100644 (file)
--- a/src/threads/interrupt.c
+++ b/src/threads/interrupt.c
@@ -1,13 +1,14 @@
-#include "interrupt.h"
+#include "threads/interrupt.h"
+#include <debug.h>
 #include <inttypes.h>
 #include <stdint.h>
-#include "intr-stubs.h"
-#include "debug.h"
-#include "io.h"
-#include "lib.h"
-#include "mmu.h"
-#include "thread.h"
-#include "timer.h"
+#include <stdio.h>
+#include "threads/flags.h"
+#include "threads/intr-stubs.h"
+#include "threads/io.h"
+#include "threads/mmu.h"
+#include "threads/thread.h"
+#include "devices/timer.h"
 
 /* Number of x86 interrupts. */
 #define INTR_CNT 256
@@ -49,8 +50,11 @@ enum intr_level
 intr_get_level (void) 
 {
   uint32_t flags;
-  
-  asm ("pushfl; popl %0" : "=g" (flags));
+
+  /* Push the flags register on the processor stack, then pop the
+     value off the stack into `flags'.  See [IA32-v2b] "PUSHF"
+     and "POP" and [IA32-v3] 5.8.1. */
+  asm volatile ("pushfl; popl %0" : "=g" (flags));
 
   return flags & FLAG_IF ? INTR_ON : INTR_OFF;
 }
@@ -68,7 +72,12 @@ enum intr_level
 intr_enable (void) 
 {
   enum intr_level old_level = intr_get_level ();
+  ASSERT (!intr_context ());
+
+  /* Enable interrupts by setting the interrupt flag.
+     See [IA32-v2b] "STI" and [IA32-v3] 5.8.1. */
   asm volatile ("sti");
+
   return old_level;
 }
 
@@ -77,7 +86,11 @@ enum intr_level
 intr_disable (void) 
 {
   enum intr_level old_level = intr_get_level ();
+
+  /* Disable interrupts by clearing the interrupt flag.
+     See [IA32-v2b] "CLI" and [IA32-v3] 5.8.1. */
   asm volatile ("cli");
+
   return old_level;
 }
 \f
@@ -91,7 +104,12 @@ intr_init (void)
   /* Initialize interrupt controller. */
   pic_init ();
 
-  /* Load IDT register. */
+  /* Initialize IDT. */
+  for (i = 0; i < INTR_CNT; i++)
+    idt[i] = make_intr_gate (intr_stubs[i], 0);
+
+  /* Load IDT register.
+     See [IA32-v2a] "LIDT" and [IA32-v3] 5.10. */
   idtr_operand = make_idtr_operand (sizeof idt - 1, idt);
   asm volatile ("lidt %0" :: "m" (idtr_operand));
 
@@ -112,6 +130,7 @@ intr_init (void)
   intr_names[11] = "#NP Segment Not Present";
   intr_names[12] = "#SS Stack Fault Exception";
   intr_names[13] = "#GP General Protection Exception";
+  intr_names[14] = "#PF Page-Fault Exception";
   intr_names[16] = "#MF x87 FPU Floating-Point Error";
   intr_names[17] = "#AC Alignment Check Exception";
   intr_names[18] = "#MC Machine-Check Exception";
@@ -299,6 +318,10 @@ intr_handler (struct intr_frame *frame)
   bool external;
   intr_handler_func *handler;
 
+  /* External interrupts are special.
+     We only handle one at a time (so interrupts must be off)
+     and they need to be acknowledged on the PIC (see below).
+     An external interrupt handler cannot sleep. */
   external = frame->vec_no >= 0x20 && frame->vec_no < 0x30;
   if (external) 
     {
@@ -338,19 +361,24 @@ intr_handler (struct intr_frame *frame)
 void
 intr_dump_frame (const struct intr_frame *f) 
 {
-  uint32_t cr2, ss;
+  uint32_t cr2;
+
+  /* Store current value of CR2 into `cr2'.
+     CR2 is the linear address of the last page fault.
+     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" (cr2));
-  asm ("movl %%ss, %0" : "=r" (ss));
 
-  printk ("Interrupt %#04x (%s) at eip=%p\n",
+  printf ("Interrupt %#04x (%s) at eip=%p\n",
           f->vec_no, intr_names[f->vec_no], f->eip);
-  printk (" cr2=%08"PRIx32" error=%08"PRIx32"\n", cr2, f->error_code);
-  printk (" eax=%08"PRIx32" ebx=%08"PRIx32" ecx=%08"PRIx32" edx=%08"PRIx32"\n",
+  printf (" cr2=%08"PRIx32" error=%08"PRIx32"\n", cr2, f->error_code);
+  printf (" eax=%08"PRIx32" ebx=%08"PRIx32" ecx=%08"PRIx32" edx=%08"PRIx32"\n",
           f->eax, f->ebx, f->ecx, f->edx);
-  printk (" esi=%08"PRIx32" edi=%08"PRIx32" esp=%08"PRIx32" ebp=%08"PRIx32"\n",
+  printf (" esi=%08"PRIx32" edi=%08"PRIx32" esp=%08"PRIx32" ebp=%08"PRIx32"\n",
           f->esi, f->edi, (uint32_t) f->esp, f->ebp);
-  printk (" cs=%04"PRIx16" ds=%04"PRIx16" es=%04"PRIx16" ss=%04"PRIx16"\n",
-          f->cs, f->ds, f->es, f->cs != SEL_KCSEG ? f->ss : ss);
+  printf (" cs=%04"PRIx16" ds=%04"PRIx16" es=%04"PRIx16" ss=%04"PRIx16"\n",
+          f->cs, f->ds, f->es, f->ss);
 }
 
 /* Returns the name of interrupt VEC. */