Fix 'prctl' system call for IRIX. At this point IRIX 5.3 static binaries

are now working for 80% of the ones I have tried. The other ones that do
not work all fail in the same way with the same messages. Once that bug
is tracked down, we should be in good shape. Task locking still needs
some work.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/sysirix.c

@@ -83,22 +83,20 @@ asmlinkage int irix_sysmp(struct pt_regs *regs)
 #define PR_RESIDENT		 9 /* Make task unswappable. */
 #define PR_ATTACHADDR		10 /* (Re-)Connect a vma to a task. */
 #define PR_DETACHADDR		11 /* Disconnect a vma from a task. */
-#define PR_TERMCHILD        12 /* When parent sleeps with fishes, kill child. */
+#define PR_TERMCHILD		12 /* Kill child if the parent dies. */
 #define PR_GETSHMASK		13 /* Get the sproc() share mask. */
 #define PR_GETNSHARE		14 /* Number of share group members. */
 #define PR_COREPID		15 /* Add task pid to name when it core. */
 #define PR_ATTACHADDRPERM	16 /* (Re-)Connect vma, with specified prot. */
-#define PR_PTHREADEXIT      17 /* Kill a pthread without prejudice. */
+#define PR_PTHREADEXIT		17 /* Kill a pthread, only for IRIX 6.[234] */
 
-asmlinkage int irix_prctl(struct pt_regs *regs)
+asmlinkage int irix_prctl(unsigned option, ...)
 {
-	unsigned long cmd;
-	int error = 0, base = 0;
+	va_list args;
+	int error = 0;
 
-	if (regs->regs[2] == 1000)
-		base = 1;
-	cmd = regs->regs[base + 4];
-	switch (cmd) {
+	va_start(args, option);
+	switch (option) {
 	case PR_MAXPROCS:
 		printk("irix_prctl[%s:%d]: Wants PR_MAXPROCS\n",
 		       current->comm, current->pid);
@@ -111,7 +109,7 @@ asmlinkage int irix_prctl(struct pt_regs *regs)
 		printk("irix_prctl[%s:%d]: Wants PR_ISBLOCKED\n",
 		       current->comm, current->pid);
 		read_lock(&tasklist_lock);
-		task = find_task_by_pid(regs->regs[base + 5]);
+		task = find_task_by_pid(va_arg(args, pid_t));
 		error = -ESRCH;
 		if (error)
 			error = (task->run_list.next != NULL);
@@ -121,7 +119,7 @@ asmlinkage int irix_prctl(struct pt_regs *regs)
 	}
 
 	case PR_SETSTACKSIZE: {
-		long value = regs->regs[base + 5];
+		long value = va_arg(args, long);
 
 		printk("irix_prctl[%s:%d]: Wants PR_SETSTACKSIZE<%08lx>\n",
 		       current->comm, current->pid, (unsigned long) value);
@@ -222,17 +220,13 @@ asmlinkage int irix_prctl(struct pt_regs *regs)
 		error = -EINVAL;
 		break;
 
-	case PR_PTHREADEXIT:
-		printk("irix_prctl[%s:%d]: Wants PR_PTHREADEXIT\n",
-		       current->comm, current->pid);
-		do_exit(regs->regs[base + 5]);
-
 	default:
 		printk("irix_prctl[%s:%d]: Non-existant opcode %d\n",
-		       current->comm, current->pid, (int)cmd);
+		       current->comm, current->pid, option);
 		error = -EINVAL;
 		break;
 	}
+	va_end(args);
 
 	return error;
 }