X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fthreads%2Finterrupt.c;h=3e522280a5b76ea5baae93e5daf8ecd4746b0028;hb=251b51f76f0594460e1cfbf2c05576fb445b861b;hp=d248d7200b71173a3d43c941ff60f094bb773f34;hpb=f2f8875638593bd5365cfd6a5ba7c9578e52322f;p=pintos-anon

diff --git a/src/threads/interrupt.c b/src/threads/interrupt.c
index d248d72..3e52228 100644
--- a/src/threads/interrupt.c
+++ b/src/threads/interrupt.c
@@ -3,6 +3,7 @@
 #include <inttypes.h>
 #include <stdint.h>
 #include <stdio.h>
+#include "threads/flags.h"
 #include "threads/intr-stubs.h"
 #include "threads/io.h"
 #include "threads/mmu.h"
@@ -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 ("pushf; pop %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;
 }
 
@@ -93,9 +106,10 @@ intr_init (void)
 
   /* Initialize IDT. */
   for (i = 0; i < INTR_CNT; i++)
-    idt[i] = make_trap_gate (intr_stubs[i], 0);
+    idt[i] = make_intr_gate (intr_stubs[i], 0);
 
-  /* Load IDT register. */
+  /* 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));
 
@@ -116,6 +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";
@@ -295,14 +310,18 @@ make_idtr_operand (uint16_t limit, void *base)
 
 /* Handler for all interrupts, faults, and exceptions.  This
    function is called by the assembly language interrupt stubs in
-   intr-stubs.S (see intr-stubs.pl).  FRAME describes the
-   interrupt and the interrupted thread's registers. */
+   intr-stubs.S.  FRAME describes the interrupt and the
+   interrupted thread's registers. */
 void
 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) 
     {
@@ -342,9 +361,14 @@ intr_handler (struct intr_frame *frame)
 void
 intr_dump_frame (const struct intr_frame *f) 
 {
-  uint32_t cr2, ss;
-  asm ("movl %%cr2, %0" : "=r" (cr2));
-  asm ("movl %%ss, %0" : "=r" (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 ("mov %0, %%cr2" : "=r" (cr2));
 
   printf ("Interrupt %#04x (%s) at eip=%p\n",
           f->vec_no, intr_names[f->vec_no], f->eip);
@@ -354,7 +378,7 @@ intr_dump_frame (const struct intr_frame *f)
   printf (" esi=%08"PRIx32" edi=%08"PRIx32" esp=%08"PRIx32" ebp=%08"PRIx32"\n",
           f->esi, f->edi, (uint32_t) f->esp, f->ebp);
   printf (" 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);
+          f->cs, f->ds, f->es, f->ss);
 }
 
 /* Returns the name of interrupt VEC. */