IA64 signal : remove redundant code in setup_sigcontext()

This patch removes some redundant code in the function setup_sigcontext().

The registers ar.ccv,b7,r14,ar.csd,ar.ssd,r2-r3 and r16-r31 are not restored in restore_sigcontext() when (flags & IA64_SC_FLAG_IN_SYSCALL) is true. So we don't need to zero those variables in setup_sigcontext().

---

diff -urp linux-2.6.24-rc3-git1.orig/arch/ia64/kernel/signal.c linux-2.6.24-rc3-git1/arch/ia64/kernel/signal.c
@@ -280,15 +280,7 @@ setup_sigcontext (struct sigcontext __us
 	err |= __copy_to_user(&sc->sc_gr[15], &scr->pt.r15, 8);		/* r15 */
 	err |= __put_user(scr->pt.cr_iip + ia64_psr(&scr->pt)->ri, &sc->sc_ip);
 
-	if (flags & IA64_SC_FLAG_IN_SYSCALL) {
-		/* Clear scratch registers if the signal interrupted a system call. */
-		err |= __put_user(0, &sc->sc_ar_ccv);				/* ar.ccv */
-		err |= __put_user(0, &sc->sc_br[7]);				/* b7 */
-		err |= __put_user(0, &sc->sc_gr[14]);				/* r14 */
-		err |= __clear_user(&sc->sc_ar25, 2*8);			/* ar.csd & ar.ssd */
-		err |= __clear_user(&sc->sc_gr[2], 2*8);			/* r2-r3 */
-		err |= __clear_user(&sc->sc_gr[16], 16*8);			/* r16-r31 */
-	} else {
+	if (!(flags & IA64_SC_FLAG_IN_SYSCALL)) {
 		/* Copy scratch regs to sigcontext if the signal didn't interrupt a syscall. */
 		err |= __put_user(scr->pt.ar_ccv, &sc->sc_ar_ccv);		/* ar.ccv */
 		err |= __put_user(scr->pt.b7, &sc->sc_br[7]);			/* b7 */

Erm, couldn't those registers contain information the process shouldn't see?

Intel are signing my paycheques ... these opinions are still mine
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."

No, this looks safe. setup_sigcontext() is stashing things out on the user stack to be used by restore_sigcontext() should the application want to return from the signal handler. But restore_sigcontext isn't actually in charge of putting values into machine registers, it just does the copy back from user space to the place where the asm code will restore registers on the way back to userland. In this instance "restored" means "set back to the state they had before the signal happened". If they aren't "restored" they'll have scratch values ... but those scratch values will have come from the application (while it was executing the signal handler). Not leaked from the kernel or from some other application.

-Tony