From beddf03109baecfdda77c6e4478ac975e49faf73 Mon Sep 17 00:00:00 2001
From: Ben Pfaff <blp@cs.stanford.edu>
Date: Thu, 2 Sep 2004 04:16:24 +0000
Subject: [PATCH] Add comments.

---
 src/threads/intr-stubs.h  | 15 +++++++++++++--
 src/threads/intr-stubs.pl |  4 +++-
 src/threads/kernel.lds.S  |  5 ++++-
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/src/threads/intr-stubs.h b/src/threads/intr-stubs.h
index b1f5039..3f2db7e 100644
--- a/src/threads/intr-stubs.h
+++ b/src/threads/intr-stubs.h
@@ -1,9 +1,20 @@
 #ifndef HEADER_INTR_STUBS_H
 #define HEADER_INTR_STUBS_H
 
-extern void (*const intr_stubs[256]) (void);
+/* Interrupt stubs.
 
-void intr_entry (void);
+   These are little snippets of code in intr-stubs.S, one for
+   each of the 256 possible x86 interrupts.  They just push the
+   interrupt vector number on the stack (and, for interrupts that
+   don't have an error code, a fake error code), then jump to
+   intr_entry().
+
+   This array points to each of the interrupt stub entry points
+   so that intr_init() can easily find them. */
+typedef void intr_stub_func (void);
+extern intr_stub_func *intr_stubs[256];
+
+/* Interrupt return path. */
 void intr_exit (void);
 
 #endif /* intr-stubs.h */
diff --git a/src/threads/intr-stubs.pl b/src/threads/intr-stubs.pl
index 22eaf59..a52f379 100755
--- a/src/threads/intr-stubs.pl
+++ b/src/threads/intr-stubs.pl
@@ -42,7 +42,7 @@ intr_entry:
 	movl %eax, %ds
 	movl %eax, %es
 
-	# Call handler.
+	# Call interrupt handler.
 	pushl %esp
 .globl intr_handler
 	call intr_handler
@@ -55,5 +55,7 @@ intr_exit:
 	popl %es
 	popl %ds
 	addl $8, %esp
+
+        # Return to caller.
 	iret
 EOF
diff --git a/src/threads/kernel.lds.S b/src/threads/kernel.lds.S
index b5426e0..b911b29 100644
--- a/src/threads/kernel.lds.S
+++ b/src/threads/kernel.lds.S
@@ -2,17 +2,20 @@
 
 OUTPUT_FORMAT("elf32-i386")
 OUTPUT_ARCH("i386")
-ENTRY(start)
+ENTRY(start)			/* Kernel starts at "start" symbol. */
 SECTIONS
 {
+  /* Specifies the virtual address for the kernel base. */
   . = LOADER_PHYS_BASE + LOADER_KERN_BASE;
 
   _start = .;
 
+  /* Kernel starts with code, followed by read-only data and writable data. */
   .text : { *(.text) } = 0x9090
   .rodata : { *(.rodata) *(.rodata.*) }
   .data : { *(.data) }
 
+  /* BSS (zero-initialized data) is after everything else. */
   _start_bss = .;
   .bss : { *(.bss) }
   _end_bss = .;
-- 
2.30.2