Merge the fueword(9) and casueword(9). In particular,

MFC r273783:
Add fueword(9) and casueword(9) functions.
MFC note: ia64 is handled like arm, with NO_FUEWORD define.

MFC r273784:
Replace some calls to fuword() by fueword() with proper error checking.

MFC r273785:
Convert kern_umtx.c to use fueword() and casueword().
MFC note: the sys__umtx_lock and sys__umtx_unlock syscalls are not
converted, they are removed from HEAD, and not used.  The do_sem2*()
family is not yet merged to stable/10, corresponding chunk will be
merged after do_sem2* are committed.

MFC r273788 (by jkim):
Actually install casuword(9) to fix build.

MFC r273911:
Add type qualifier volatile to the base (userspace) address argument
of fuword(9) and suword(9).

2 files changed, 27 insertions, 14 deletions

diff --git a/sys/i386/i386/support.s b/sys/i386/i386/support.s
index c126f78..0a08012 100644
--- a/sys/i386/i386/support.s
+++ b/sys/i386/i386/support.s
@@ -389,16 +389,16 @@ copyin_fault:
 	ret
 
 /*
- * casuword.  Compare and set user word.  Returns -1 or the current value.
+ * casueword.  Compare and set user word.  Returns -1 on fault,
+ * 0 on non-faulting access.  The current value is in *oldp.
  */
-
-ALTENTRY(casuword32)
-ENTRY(casuword)
+ALTENTRY(casueword32)
+ENTRY(casueword)
 	movl	PCPU(CURPCB),%ecx
 	movl	$fusufault,PCB_ONFAULT(%ecx)
 	movl	4(%esp),%edx			/* dst */
 	movl	8(%esp),%eax			/* old */
-	movl	12(%esp),%ecx			/* new */
+	movl	16(%esp),%ecx			/* new */
 
 	cmpl	$VM_MAXUSER_ADDRESS-4,%edx	/* verify address is valid */
 	ja	fusufault
@@ -416,17 +416,20 @@ ENTRY(casuword)
 
 	movl	PCPU(CURPCB),%ecx
 	movl	$0,PCB_ONFAULT(%ecx)
+	movl	12(%esp),%edx			/* oldp */
+	movl	%eax,(%edx)
+	xorl	%eax,%eax
 	ret
-END(casuword32)
-END(casuword)
+END(casueword32)
+END(casueword)
 
 /*
  * Fetch (load) a 32-bit word, a 16-bit word, or an 8-bit byte from user
- * memory.  All these functions are MPSAFE.
+ * memory.
  */
 
-ALTENTRY(fuword32)
-ENTRY(fuword)
+ALTENTRY(fueword32)
+ENTRY(fueword)
 	movl	PCPU(CURPCB),%ecx
 	movl	$fusufault,PCB_ONFAULT(%ecx)
 	movl	4(%esp),%edx			/* from */
@@ -436,9 +439,12 @@ ENTRY(fuword)
 
 	movl	(%edx),%eax
 	movl	$0,PCB_ONFAULT(%ecx)
+	movl	8(%esp),%edx
+	movl	%eax,(%edx)
+	xorl	%eax,%eax
 	ret
-END(fuword32)
-END(fuword)
+END(fueword32)
+END(fueword)
 
 /*
  * fuswintr() and suswintr() are specialized variants of fuword16() and
diff --git a/sys/i386/i386/trap.c b/sys/i386/i386/trap.c
index e654fe0..152addf 100644
--- a/sys/i386/i386/trap.c
+++ b/sys/i386/i386/trap.c
@@ -1062,6 +1062,7 @@ cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
 	struct proc *p;
 	struct trapframe *frame;
 	caddr_t params;
+	long tmp;
 	int error;
 
 	p = td->td_proc;
@@ -1077,14 +1078,20 @@ cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
 		/*
 		 * Code is first argument, followed by actual args.
 		 */
-		sa->code = fuword(params);
+		error = fueword(params, &tmp);
+		if (error == -1)
+			return (EFAULT);
+		sa->code = tmp;
 		params += sizeof(int);
 	} else if (sa->code == SYS___syscall) {
 		/*
 		 * Like syscall, but code is a quad, so as to maintain
 		 * quad alignment for the rest of the arguments.
 		 */
-		sa->code = fuword(params);
+		error = fueword(params, &tmp);
+		if (error == -1)
+			return (EFAULT);
+		sa->code = tmp;
 		params += sizeof(quad_t);
 	}