Trace syscall complete, kernel interface and userspace demo program

Makefile

@@ -138,6 +138,7 @@ UPROGS=\
 	$U/_clear\
 	$U/_halt\
 	$U/_reset\
+	$U/_traced\
 
 fs.img: mkfs/mkfs README.md $(UPROGS)
 	mkfs/mkfs fs.img README.md $(UPROGS)

kernel/exec.c

@@ -127,6 +127,7 @@ exec(char *path, char **argv)
   p->sz = sz;
   p->trapframe->epc = elf.entry; // initial program counter = main
   p->trapframe->sp = sp;         // initial stack pointer
+  p->mask = 0;
   proc_freepagetable(oldpagetable, oldsz);
 
   return argc; // this ends up in a0, the first argument to main(argc, argv)

kernel/proc.c

@@ -112,6 +112,7 @@ allocproc(void)
   struct proc *p;
 
   for(p = proc; p < &proc[NPROC]; p++) {
+    p->mask = 0;
     acquire(&p->lock);
     if(p->state == UNUSED) {
       goto found;
@@ -304,6 +305,7 @@ fork(void)
   safestrcpy(np->name, p->name, sizeof(p->name));
 
   pid = np->pid;
+  np->mask = 0;
 
   release(&np->lock);
 

kernel/syscall.c

@@ -124,6 +124,10 @@ syscall(void)
 
   num = p->trapframe->a7;
   if(num > 0 && num < NELEM(syscalls) && syscalls[num]) {
+    if(p->mask & (1 << num)) {
+      printf("%d %s: Trace: syscall #%d\n", p->pid, p->name, num);
+    }
+
     // Use num to lookup the system call function for num, call it,
     // and store its return value in p->trapframe->a0
     p->trapframe->a0 = syscalls[num]();

kernel/sysproc.c

@@ -93,7 +93,10 @@ sys_uptime(void)
 u64
 sys_trace(void)
 {
-  /* TODO: Implement sys_trace */
+  int mask;
+  argint(0, &mask);
+
+  myproc()->mask = mask;
   return 0;
 }
 

user/traced.c

@@ -0,0 +1,18 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+#include "kernel/syscall.h"
+
+int
+main(int argc, char *argv[])
+{
+  trace(1 << SYS_open);
+  int fd;
+
+  if((fd = open(argv[1], 0)) < 0) {
+    fprintf(stderr, "Traced: cannot open %s\n", argv[1]);
+    exit(1);
+  }
+
+  exit(0);
+}

user/user.h

@@ -2,6 +2,9 @@
 
 #include "../kernel/types.h"
 
+#define stderr 2
+#define stdout 1
+
 struct stat;
 
 /**