[IA64] ptrace and restore_sigcontext() allow ar.rsc.pl==0

This patch fixes handling of accesses to ar.rsc via ptrace & restore_sigcontext
[With Thanks to Chris Wright for noticing the restore_sigcontext path]
Signed-off-by: Matthew Chapman <matthewc@hp.com>
Acked-by: David Mosberger <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/ptrace.c

@@ -945,6 +945,13 @@ access_uarea (struct task_struct *child, unsigned long addr,
 				*data = (pt->cr_ipsr & IPSR_MASK);
 			return 0;
 
+		      case PT_AR_RSC:
+			if (write_access)
+				pt->ar_rsc = *data | (3 << 2); /* force PL3 */
+			else
+				*data = pt->ar_rsc;
+			return 0;
+
 		      case PT_AR_RNAT:
 			urbs_end = ia64_get_user_rbs_end(child, pt, NULL);
 			rnat_addr = (long) ia64_rse_rnat_addr((long *)
@@ -996,9 +1003,6 @@ access_uarea (struct task_struct *child, unsigned long addr,
 		      case PT_AR_BSPSTORE:
 			ptr = pt_reg_addr(pt, ar_bspstore);
 			break;
-		      case PT_AR_RSC:
-			ptr = pt_reg_addr(pt, ar_rsc);
-			break;
 		      case PT_AR_UNAT:
 			ptr = pt_reg_addr(pt, ar_unat);
 			break;
@@ -1234,7 +1238,7 @@ ptrace_getregs (struct task_struct *child, struct pt_all_user_regs __user *ppr)
 static long
 ptrace_setregs (struct task_struct *child, struct pt_all_user_regs __user *ppr)
 {
-	unsigned long psr, ec, lc, rnat, bsp, cfm, nat_bits, val = 0;
+	unsigned long psr, rsc, ec, lc, rnat, bsp, cfm, nat_bits, val = 0;
 	struct unw_frame_info info;
 	struct switch_stack *sw;
 	struct ia64_fpreg fpval;
@@ -1267,7 +1271,7 @@ ptrace_setregs (struct task_struct *child, struct pt_all_user_regs __user *ppr)
 	/* app regs */
 
 	retval |= __get_user(pt->ar_pfs, &ppr->ar[PT_AUR_PFS]);
-	retval |= __get_user(pt->ar_rsc, &ppr->ar[PT_AUR_RSC]);
+	retval |= __get_user(rsc, &ppr->ar[PT_AUR_RSC]);
 	retval |= __get_user(pt->ar_bspstore, &ppr->ar[PT_AUR_BSPSTORE]);
 	retval |= __get_user(pt->ar_unat, &ppr->ar[PT_AUR_UNAT]);
 	retval |= __get_user(pt->ar_ccv, &ppr->ar[PT_AUR_CCV]);
@@ -1365,6 +1369,7 @@ ptrace_setregs (struct task_struct *child, struct pt_all_user_regs __user *ppr)
 	retval |= __get_user(nat_bits, &ppr->nat);
 
 	retval |= access_uarea(child, PT_CR_IPSR, &psr, 1);
+	retval |= access_uarea(child, PT_AR_RSC, &rsc, 1);
 	retval |= access_uarea(child, PT_AR_EC, &ec, 1);
 	retval |= access_uarea(child, PT_AR_LC, &lc, 1);
 	retval |= access_uarea(child, PT_AR_RNAT, &rnat, 1);

arch/ia64/kernel/signal.c

@@ -94,7 +94,7 @@ sys_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, long arg2,
 static long
 restore_sigcontext (struct sigcontext __user *sc, struct sigscratch *scr)
 {
-	unsigned long ip, flags, nat, um, cfm;
+	unsigned long ip, flags, nat, um, cfm, rsc;
 	long err;
 
 	/* Always make any pending restarted system calls return -EINTR */
@@ -106,7 +106,7 @@ restore_sigcontext (struct sigcontext __user *sc, struct sigscratch *scr)
 	err |= __get_user(ip, &sc->sc_ip);			/* instruction pointer */
 	err |= __get_user(cfm, &sc->sc_cfm);
 	err |= __get_user(um, &sc->sc_um);			/* user mask */
-	err |= __get_user(scr->pt.ar_rsc, &sc->sc_ar_rsc);
+	err |= __get_user(rsc, &sc->sc_ar_rsc);
 	err |= __get_user(scr->pt.ar_unat, &sc->sc_ar_unat);
 	err |= __get_user(scr->pt.ar_fpsr, &sc->sc_ar_fpsr);
 	err |= __get_user(scr->pt.ar_pfs, &sc->sc_ar_pfs);
@@ -119,6 +119,7 @@ restore_sigcontext (struct sigcontext __user *sc, struct sigscratch *scr)
 	err |= __copy_from_user(&scr->pt.r15, &sc->sc_gr[15], 8);	/* r15 */
 
 	scr->pt.cr_ifs = cfm | (1UL << 63);
+	scr->pt.ar_rsc = rsc | (3 << 2); /* force PL3 */
 
 	/* establish new instruction pointer: */
 	scr->pt.cr_iip = ip & ~0x3UL;