Unused includes

Makefile

@@ -135,6 +135,7 @@ UPROGS=\
 	$U/_wc\
 	$U/_zombie\
 	$U/_clear\
+	$U/_halt\
 
 fs.img: mkfs/mkfs README.md $(UPROGS)
 	mkfs/mkfs fs.img README.md $(UPROGS)

kernel/defs.h

@@ -64,10 +64,34 @@ void ramdiskinit(void);
 void ramdiskintr(void);
 void ramdiskrw(struct buf *);
 
-// kalloc.c
+/**
+ * Kernel memory allocator
+ *
+ * Allocate one 4096-byte page of physical memory.
+ * Returns a pointer that the kernel can use.
+ * Returns 0 if the memory cannot be allocated.
+ * See: kalloc.c
+ */
 void *kalloc(void);
-void  kfree(void *);
-void  kinit(void);
+
+/**
+ * Kernel memory allocator
+ *
+ * Free the page of physical memory pointed at by pa,
+ * which normally should have been returned by a
+ * call to kalloc().  (The exception is when
+ * initializing the allocator; see kinit above.)
+ * See: kalloc.c
+ */
+void kfree(void *);
+
+/**
+ * Initialize kernel memory allocator
+ *
+ * Called by main() on the way to the kernel's main loop.
+ * See: kalloc.c
+ */
+void kinit(void);
 
 // log.c
 void initlog(int, struct superblock *);

kernel/kalloc.c

@@ -3,21 +3,23 @@
 // and pipe buffers. Allocates whole 4096-byte pages.
 
 #include "types.h"
-#include "param.h"
 #include "memlayout.h"
 #include "spinlock.h"
 #include "riscv.h"
 #include "defs.h"
 
+/** Free list of physical pages. */
 void freerange(void *pa_start, void *pa_end);
 
-extern char end[]; // first address after kernel.
-                   // defined by kernel.ld.
+/** first address after kernel. defined by kernel.ld. */
+extern char end[];
 
+/** A run is a node in the free list. */
 struct run {
   struct run *next;
 };
 
+/** Kernel memory allocator. */
 struct {
   struct spinlock lock;
   struct run     *freelist;
@@ -39,10 +41,6 @@ freerange(void *pa_start, void *pa_end)
     kfree(p);
 }
 
-// Free the page of physical memory pointed at by pa,
-// which normally should have been returned by a
-// call to kalloc().  (The exception is when
-// initializing the allocator; see kinit above.)
 void
 kfree(void *pa)
 {
@@ -62,9 +60,6 @@ kfree(void *pa)
   release(&kmem.lock);
 }
 
-// Allocate one 4096-byte page of physical memory.
-// Returns a pointer that the kernel can use.
-// Returns 0 if the memory cannot be allocated.
 void *
 kalloc(void)
 {

kernel/kernel.ld

@@ -15,12 +15,25 @@ SECTIONS
    * that reference the functions in your object file.
    */
   .text : {
+    /* Match any section that starts with .text. */
     *(.text .text.*)
+
+    /* Align the next section to a 4KB (page) boundary. */
     . = ALIGN(0x1000);
+
+    /* Put the trampoline code here. */
     _trampoline = .;
+
+    /* Match any section that starts with .trampsec. */
     *(trampsec)
+
+    /* Align the next section to a 4KB (page) boundary. */
     . = ALIGN(0x1000);
+
+    /* Assert that the trampoline code is exactly 4KB (page) in size. */
     ASSERT(. - _trampoline == 0x1000, "error: trampoline larger than one page");
+
+    /* Define symbol etext to be the current location. */
     PROVIDE(etext = .);
   }
 
@@ -29,6 +42,7 @@ SECTIONS
    * It is not unusual to find this data interleaved with the text section.
    */
   .rodata : {
+    /* Align on quadword boundary. */
     . = ALIGN(16);
     *(.srodata .srodata.*) /* do not need to distinguish this from .rodata */
     . = ALIGN(16);
@@ -59,6 +73,6 @@ SECTIONS
     *(.bss .bss.*)
   }
 
-  /* PROVIDE, see vm.c */
+  /* Define symbol end as current location, note that this is not aligned, see vm.c */
   PROVIDE(end = .);
 }

kernel/proc.c

@@ -650,9 +650,8 @@ either_copyin(void *dst, int user_src, u64 src, u64 len)
 void
 procdump(void)
 {
-  static char *states[] = {
-    [UNUSED] "unused", [USED] "used", [SLEEPING] "sleep ", [RUNNABLE] "runble", [RUNNING] "run   ", [ZOMBIE] "zombie"
-  };
+  static char *states[] = { [UNUSED] = "unused",   [USED] = "used",      [SLEEPING] = "sleep ",
+                            [RUNNABLE] = "runble", [RUNNING] = "run   ", [ZOMBIE] = "zombie" };
   struct proc *p;
   char        *state;
 

kernel/syscall.c

@@ -102,6 +102,7 @@ extern u64 sys_link(void);
 extern u64 sys_mkdir(void);
 extern u64 sys_close(void);
 extern u64 sys_trace(void);
+extern u64 sys_halt(void);
 
 // An array mapping syscall numbers from syscall.h
 // to the function that handles the system call.
@@ -111,7 +112,7 @@ static u64 (*syscalls[])(void) = {
   [SYS_chdir] = sys_chdir, [SYS_dup] = sys_dup,       [SYS_getpid] = sys_getpid, [SYS_sbrk] = sys_sbrk,
   [SYS_sleep] = sys_sleep, [SYS_uptime] = sys_uptime, [SYS_open] = sys_open,     [SYS_write] = sys_write,
   [SYS_mknod] = sys_mknod, [SYS_unlink] = sys_unlink, [SYS_link] = sys_link,     [SYS_mkdir] = sys_mkdir,
-  [SYS_close] = sys_close, [SYS_trace] = sys_trace,
+  [SYS_close] = sys_close, [SYS_trace] = sys_trace,   [SYS_halt] = sys_halt,
 };
 
 void

kernel/syscall.h

@@ -23,3 +23,4 @@
 #define SYS_mkdir  20
 #define SYS_close  21
 #define SYS_trace  22
+#define SYS_halt   23

kernel/sysproc.c

@@ -96,3 +96,9 @@ sys_trace(void)
   /* TODO: Implement sys_trace */
   return 0;
 }
+
+void
+sys_halt(void)
+{
+  /* TODO: Implement sys_halt */
+}

kernel/trap.c

@@ -1,5 +1,4 @@
 #include "types.h"
-#include "param.h"
 #include "memlayout.h"
 #include "riscv.h"
 #include "spinlock.h"

user/halt.c

@@ -0,0 +1,9 @@
+#include "user.h"
+
+/** Stops the machine */
+int
+main(int argc, char *argv[])
+{
+  halt();
+  return 0;
+}

user/user.h

@@ -74,6 +74,9 @@ int uptime(void);
 /** trace */
 int trace(int);
 
+/** halt */
+void halt(void);
+
 /**
  * Library functions (ulib.c)
  */

user/usys.pl

@@ -14,7 +14,7 @@ sub entry {
     print " ecall\n";
     print " ret\n";
 }
-	
+
 entry("fork");
 entry("exit");
 entry("wait");
@@ -37,3 +37,4 @@ entry("sbrk");
 entry("sleep");
 entry("uptime");
 entry("trace");
+entry("halt");