[S390] allow all addressing modes

The user space program can change its addressing mode between the
24-bit, 31-bit and the 64-bit mode if the kernel is 64 bit. Currently
the kernel always forces the standard amode on signal delivery and
signal return and on ptrace: 64-bit for a 64-bit process, 31-bit for
a compat process and 31-bit kernels. Change the signal and ptrace code
to allow the full range of addressing modes. Signal handlers are
run in the standard addressing mode for the process.

One caveat is that even an 31-bit compat process can switch to the
64-bit mode. The next signal will switch back into the 31-bit mode
and there is no room in the 31-bit compat signal frame to store the
information that the program came from the 64-bit mode.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/ptrace.h

@@ -269,7 +269,7 @@ typedef struct
 #define PSW_MASK_EA		0x0000000100000000UL
 #define PSW_MASK_BA		0x0000000080000000UL
 
-#define PSW_MASK_USER		0x00003F0000000000UL
+#define PSW_MASK_USER		0x00003F0180000000UL
 
 #define PSW_ADDR_AMODE		0x0000000000000000UL
 #define PSW_ADDR_INSN		0xFFFFFFFFFFFFFFFFUL

arch/s390/kernel/compat_signal.c

@@ -302,7 +302,8 @@ static int save_sigregs32(struct pt_regs *regs, _sigregs32 __user *sregs)
 
 	regs32.psw.mask = psw32_user_bits |
 		((__u32)(regs->psw.mask >> 32) & PSW32_MASK_USER);
-	regs32.psw.addr = PSW32_ADDR_AMODE | (__u32) regs->psw.addr;
+	regs32.psw.addr = (__u32) regs->psw.addr |
+		(__u32)(regs->psw.mask & PSW_MASK_BA);
 	for (i = 0; i < NUM_GPRS; i++)
 		regs32.gprs[i] = (__u32) regs->gprs[i];
 	save_access_regs(current->thread.acrs);
@@ -328,7 +329,8 @@ static int restore_sigregs32(struct pt_regs *regs,_sigregs32 __user *sregs)
 	if (err)
 		return err;
 	regs->psw.mask = (regs->psw.mask & ~PSW_MASK_USER) |
-		(__u64)(regs32.psw.mask & PSW32_MASK_USER) << 32;
+		(__u64)(regs32.psw.mask & PSW32_MASK_USER) << 32 |
+		(__u64)(regs32.psw.addr & PSW32_ADDR_AMODE);
 	regs->psw.addr = (__u64)(regs32.psw.addr & PSW32_ADDR_INSN);
 	for (i = 0; i < NUM_GPRS; i++)
 		regs->gprs[i] = (__u64) regs32.gprs[i];
@@ -496,9 +498,9 @@ static int setup_frame32(int sig, struct k_sigaction *ka,
 	/* Set up to return from userspace.  If provided, use a stub
 	   already in userspace.  */
 	if (ka->sa.sa_flags & SA_RESTORER) {
-		regs->gprs[14] = (__u64) ka->sa.sa_restorer;
+		regs->gprs[14] = (__u64) ka->sa.sa_restorer | PSW32_ADDR_AMODE;
 	} else {
-		regs->gprs[14] = (__u64) frame->retcode;
+		regs->gprs[14] = (__u64) frame->retcode | PSW32_ADDR_AMODE;
 		if (__put_user(S390_SYSCALL_OPCODE | __NR_sigreturn,
 		               (u16 __user *)(frame->retcode)))
 			goto give_sigsegv;
@@ -510,6 +512,7 @@ static int setup_frame32(int sig, struct k_sigaction *ka,
 
 	/* Set up registers for signal handler */
 	regs->gprs[15] = (__u64) frame;
+	regs->psw.mask |= PSW_MASK_BA;		/* force amode 31 */
 	regs->psw.addr = (__u64) ka->sa.sa_handler;
 
 	regs->gprs[2] = map_signal(sig);
@@ -573,6 +576,7 @@ static int setup_rt_frame32(int sig, struct k_sigaction *ka, siginfo_t *info,
 
 	/* Set up registers for signal handler */
 	regs->gprs[15] = (__u64) frame;
+	regs->psw.mask |= PSW_MASK_BA;		/* force amode 31 */
 	regs->psw.addr = (__u64) ka->sa.sa_handler;
 
 	regs->gprs[2] = map_signal(sig);

arch/s390/kernel/ptrace.c

@@ -170,8 +170,7 @@ static unsigned long __peek_user(struct task_struct *child, addr_t addr)
 		tmp = *(addr_t *)((addr_t) &task_pt_regs(child)->psw + addr);
 		if (addr == (addr_t) &dummy->regs.psw.mask)
 			/* Return a clean psw mask. */
-			tmp = psw_user_bits | (tmp & PSW_MASK_USER) |
-				PSW_MASK_EA | PSW_MASK_BA;
+			tmp = psw_user_bits | (tmp & PSW_MASK_USER);
 
 	} else if (addr < (addr_t) &dummy->regs.orig_gpr2) {
 		/*
@@ -286,26 +285,17 @@ static inline void __poke_user_per(struct task_struct *child,
 static int __poke_user(struct task_struct *child, addr_t addr, addr_t data)
 {
 	struct user *dummy = NULL;
-	addr_t offset, tmp;
+	addr_t offset;
 
 	if (addr < (addr_t) &dummy->regs.acrs) {
 		/*
 		 * psw and gprs are stored on the stack
 		 */
-		tmp = (data & ~PSW_MASK_USER) ^ psw_user_bits;
 		if (addr == (addr_t) &dummy->regs.psw.mask &&
-#ifdef CONFIG_COMPAT
-		    tmp != PSW_MASK_BA &&
-#endif
-		    tmp != (PSW_MASK_EA | PSW_MASK_BA))
+		    ((data & ~PSW_MASK_USER) != psw_user_bits ||
+		     ((data & PSW_MASK_EA) && !(data & PSW_MASK_BA))))
 			/* Invalid psw mask. */
 			return -EINVAL;
-#ifndef CONFIG_64BIT
-		if (addr == (addr_t) &dummy->regs.psw.addr)
-			/* I'd like to reject addresses without the
-			   high order bit but older gdb's rely on it */
-			data |= PSW_ADDR_AMODE;
-#endif
 		if (addr == (addr_t) &dummy->regs.psw.addr)
 			/*
 			 * The debugger changed the instruction address,
@@ -517,7 +507,8 @@ static u32 __peek_user_compat(struct task_struct *child, addr_t addr)
 			tmp = psw32_user_bits | (tmp & PSW32_MASK_USER);
 		} else if (addr == (addr_t) &dummy32->regs.psw.addr) {
 			/* Fake a 31 bit psw address. */
-			tmp = (__u32) regs->psw.addr | PSW32_ADDR_AMODE;
+			tmp = (__u32) regs->psw.addr |
+				(__u32)(regs->psw.mask & PSW_MASK_BA);
 		} else {
 			/* gpr 0-15 */
 			tmp = *(__u32 *)((addr_t) &regs->psw + addr*2 + 4);
@@ -615,10 +606,14 @@ static int __poke_user_compat(struct task_struct *child,
 				/* Invalid psw mask. */
 				return -EINVAL;
 			regs->psw.mask = (regs->psw.mask & ~PSW_MASK_USER) |
+				(regs->psw.mask & PSW_MASK_BA) |
 				(__u64)(tmp & PSW32_MASK_USER) << 32;
 		} else if (addr == (addr_t) &dummy32->regs.psw.addr) {
 			/* Build a 64 bit psw address from 31 bit address. */
 			regs->psw.addr = (__u64) tmp & PSW32_ADDR_INSN;
+			/* Transfer 31 bit amode bit to psw mask. */
+			regs->psw.mask = (regs->psw.mask & ~PSW_MASK_BA) |
+				(__u64)(tmp & PSW32_ADDR_AMODE);
 			/*
 			 * The debugger changed the instruction address,
 			 * reset system call restart, see signal.c:do_signal

arch/s390/kernel/signal.c

@@ -117,7 +117,7 @@ static int save_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
 
 	/* Copy a 'clean' PSW mask to the user to avoid leaking
 	   information about whether PER is currently on.  */
-	user_sregs.regs.psw.mask = psw_user_bits | PSW_MASK_EA | PSW_MASK_BA |
+	user_sregs.regs.psw.mask = psw_user_bits |
 		(regs->psw.mask & PSW_MASK_USER);
 	user_sregs.regs.psw.addr = regs->psw.addr;
 	memcpy(&user_sregs.regs.gprs, &regs->gprs, sizeof(sregs->regs.gprs));
@@ -145,9 +145,13 @@ static int restore_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
 	err = __copy_from_user(&user_sregs, sregs, sizeof(_sigregs));
 	if (err)
 		return err;
+	/* Use regs->psw.mask instead of psw_user_bits to preserve PER bit. */
 	regs->psw.mask = (regs->psw.mask & ~PSW_MASK_USER) |
 		(user_sregs.regs.psw.mask & PSW_MASK_USER);
-	regs->psw.addr = PSW_ADDR_AMODE | user_sregs.regs.psw.addr;
+	/* Check for invalid amode */
+	if (regs->psw.mask & PSW_MASK_EA)
+		regs->psw.mask |= PSW_MASK_BA;
+	regs->psw.addr = user_sregs.regs.psw.addr;
 	memcpy(&regs->gprs, &user_sregs.regs.gprs, sizeof(sregs->regs.gprs));
 	memcpy(&current->thread.acrs, &user_sregs.regs.acrs,
 	       sizeof(sregs->regs.acrs));
@@ -290,6 +294,7 @@ static int setup_frame(int sig, struct k_sigaction *ka,
 
 	/* Set up registers for signal handler */
 	regs->gprs[15] = (unsigned long) frame;
+	regs->psw.mask |= PSW_MASK_EA | PSW_MASK_BA;	/* 64 bit amode */
 	regs->psw.addr = (unsigned long) ka->sa.sa_handler | PSW_ADDR_AMODE;
 
 	regs->gprs[2] = map_signal(sig);
@@ -358,6 +363,7 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 
 	/* Set up registers for signal handler */
 	regs->gprs[15] = (unsigned long) frame;
+	regs->psw.mask |= PSW_MASK_EA | PSW_MASK_BA;	/* 64 bit amode */
 	regs->psw.addr = (unsigned long) ka->sa.sa_handler | PSW_ADDR_AMODE;
 
 	regs->gprs[2] = map_signal(sig);