[S390] fix system call parameter functions.

syscall_get_nr() currently returns a valid result only if the call
chain of the traced process includes do_syscall_trace_enter(). But
collect_syscall() can be called for any sleeping task, the result of
syscall_get_nr() in general is completely bogus.

To make syscall_get_nr() work for any sleeping task the traps field
in pt_regs is replace with svcnr - the system call number the process
is executing. If svcnr == 0 the process is not on a system call path.

The syscall_get_arguments and syscall_set_arguments use regs->gprs[2]
for the first system call parameter. This is incorrect since gprs[2]
may have been overwritten with the system call number if the call
chain includes do_syscall_trace_enter. Use regs->orig_gprs2 instead.

Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/include/asm/ptrace.h

···
 	psw_t psw;
 	unsigned long gprs[NUM_GPRS];
 	unsigned long orig_gpr2;
+	unsigned short svcnr;
 	unsigned short ilc;
-	unsigned short trap;
 };
 #endif
 

arch/s390/include/asm/syscall.h

···
 static inline long syscall_get_nr(struct task_struct *task,
 				  struct pt_regs *regs)
 {
-	if (regs->trap != __LC_SVC_OLD_PSW)
-		return -1;
-	return regs->gprs[2];
+	return regs->svcnr ? regs->svcnr : -1;
 }
 
 static inline void syscall_rollback(struct task_struct *task,
···
 					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
+	unsigned long mask = -1UL;
+
 	BUG_ON(i + n > 6);
 #ifdef CONFIG_COMPAT
-	if (test_tsk_thread_flag(task, TIF_31BIT)) {
-		if (i + n == 6)
-			args[--n] = (u32) regs->args[0];
-		while (n-- > 0)
-			args[n] = (u32) regs->gprs[2 + i + n];
-	}
+	if (test_tsk_thread_flag(task, TIF_31BIT))
+		mask = 0xffffffff;
 #endif
 	if (i + n == 6)
-		args[--n] = regs->args[0];
-	memcpy(args, &regs->gprs[2 + i], n * sizeof(args[0]));
+		args[--n] = regs->args[0] & mask;
+	while (n-- > 0)
+		if (i + n > 0)
+			args[n] = regs->gprs[2 + i + n] & mask;
+	if (i == 0)
+		args[0] = regs->orig_gpr2 & mask;
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,
···
 	BUG_ON(i + n > 6);
 	if (i + n == 6)
 		regs->args[0] = args[--n];
-	memcpy(&regs->gprs[2 + i], args, n * sizeof(args[0]));
+	while (n-- > 0)
+		if (i + n > 0)
+			regs->gprs[2 + i + n] = args[n];
+	if (i == 0)
+		regs->orig_gpr2 = args[0];
 }
 
 #endif	/* _ASM_SYSCALL_H */

arch/s390/kernel/asm-offsets.c

···
 	DEFINE(__PT_GPRS, offsetof(struct pt_regs, gprs));
 	DEFINE(__PT_ORIG_GPR2, offsetof(struct pt_regs, orig_gpr2));
 	DEFINE(__PT_ILC, offsetof(struct pt_regs, ilc));
-	DEFINE(__PT_TRAP, offsetof(struct pt_regs, trap));
+	DEFINE(__PT_SVCNR, offsetof(struct pt_regs, svcnr));
 	DEFINE(__PT_SIZE, sizeof(struct pt_regs));
 	BLANK();
 	DEFINE(__SF_BACKCHAIN, offsetof(struct stack_frame, back_chain));

arch/s390/kernel/compat_signal.c

···
 		return err;
 
 	restore_fp_regs(&current->thread.fp_regs);
-	regs->trap = -1;	/* disable syscall checks */
+	regs->svcnr = 0;	/* disable syscall checks */
 	return 0;
 }
 

arch/s390/kernel/entry.S

···
 SP_R15	     =	STACK_FRAME_OVERHEAD + __PT_GPRS + 60
 SP_ORIG_R2   =	STACK_FRAME_OVERHEAD + __PT_ORIG_GPR2
 SP_ILC	     =	STACK_FRAME_OVERHEAD + __PT_ILC
-SP_TRAP      =	STACK_FRAME_OVERHEAD + __PT_TRAP
+SP_SVCNR     =	STACK_FRAME_OVERHEAD + __PT_SVCNR
 SP_SIZE      =	STACK_FRAME_OVERHEAD + __PT_SIZE
 
 _TIF_WORK_SVC = (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \
···
 	.macro	CREATE_STACK_FRAME psworg,savearea
 	s	%r15,BASED(.Lc_spsize)	# make room for registers & psw
 	mvc	SP_PSW(8,%r15),0(%r12)	# move user PSW to stack
-	la	%r12,\psworg
 	st	%r2,SP_ORIG_R2(%r15)	# store original content of gpr 2
-	icm	%r12,12,__LC_SVC_ILC
+	icm	%r12,3,__LC_SVC_ILC
 	stm	%r0,%r11,SP_R0(%r15)	# store gprs %r0-%r11 to kernel stack
-	st	%r12,SP_ILC(%r15)
+	st	%r12,SP_SVCNR(%r15)
 	mvc	SP_R12(16,%r15),\savearea # move %r12-%r15 to stack
 	la	%r12,0
 	st	%r12,__SF_BACKCHAIN(%r15)	# clear back chain
···
 #endif
 sysc_do_svc:
 	l	%r9,__LC_THREAD_INFO	# load pointer to thread_info struct
-	sla	%r7,2			# *4 and test for svc 0
+	ltr	%r7,%r7			# test for svc 0
 	bnz	BASED(sysc_nr_ok)	# svc number > 0
 	# svc 0: system call number in %r1
 	cl	%r1,BASED(.Lnr_syscalls)
 	bnl	BASED(sysc_nr_ok)
 	lr	%r7,%r1 	  # copy svc number to %r7
-	sla	%r7,2		  # *4
 sysc_nr_ok:
 	mvc	SP_ARGS(4,%r15),SP_R7(%r15)
 sysc_do_restart:
+	sth	%r7,SP_SVCNR(%r15)
+	sll	%r7,2		  # svc number *4
 	l	%r8,BASED(.Lsysc_table)
 	tm	__TI_flags+3(%r9),(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT)
 	l	%r8,0(%r7,%r8)	  # get system call addr.
···
 sysc_restart:
 	ni	__TI_flags+3(%r9),255-_TIF_RESTART_SVC # clear TIF_RESTART_SVC
 	l	%r7,SP_R2(%r15) 	# load new svc number
-	sla	%r7,2
 	mvc	SP_R2(4,%r15),SP_ORIG_R2(%r15) # restore first argument
 	lm	%r2,%r6,SP_R2(%r15)	# load svc arguments
 	b	BASED(sysc_do_restart)	# restart svc
···
 #
 sysc_singlestep:
 	ni	__TI_flags+3(%r9),255-_TIF_SINGLE_STEP # clear TIF_SINGLE_STEP
-	mvi	SP_TRAP+1(%r15),0x28	# set trap indication to pgm check
+	mvi	SP_SVCNR(%r15),0xff	# set trap indication to pgm check
+	mvi	SP_SVCNR+1(%r15),0xff
 	la	%r2,SP_PTREGS(%r15)	# address of register-save area
 	l	%r1,BASED(.Lhandle_per)	# load adr. of per handler
 	la	%r14,BASED(sysc_return)	# load adr. of system return
···
 	bnl	BASED(sysc_tracenogo)
 	l	%r8,BASED(.Lsysc_table)
 	lr	%r7,%r2
-	sll	%r7,2			# *4
+	sll	%r7,2			# svc number *4
 	l	%r8,0(%r7,%r8)
 sysc_tracego:
 	lm	%r3,%r6,SP_R3(%r15)
···
 # per was called from kernel, must be kprobes
 #
 kernel_per:
-	mvi	SP_TRAP+1(%r15),0x28	# set trap indication to pgm check
+	mvi	SP_SVCNR(%r15),0xff	# set trap indication to pgm check
+	mvi	SP_SVCNR+1(%r15),0xff
 	la	%r2,SP_PTREGS(%r15)	# address of register-save area
 	l	%r1,BASED(.Lhandle_per)	# load adr. of per handler
 	la	%r14,BASED(sysc_restore)# load adr. of system return

arch/s390/kernel/entry64.S

···
 SP_R15	     =	STACK_FRAME_OVERHEAD + __PT_GPRS + 120
 SP_ORIG_R2   =	STACK_FRAME_OVERHEAD + __PT_ORIG_GPR2
 SP_ILC	     =	STACK_FRAME_OVERHEAD + __PT_ILC
-SP_TRAP      =	STACK_FRAME_OVERHEAD + __PT_TRAP
+SP_SVCNR      =	STACK_FRAME_OVERHEAD + __PT_SVCNR
 SP_SIZE      =	STACK_FRAME_OVERHEAD + __PT_SIZE
 
 STACK_SHIFT = PAGE_SHIFT + THREAD_ORDER
···
 	.macro	CREATE_STACK_FRAME psworg,savearea
 	aghi	%r15,-SP_SIZE		# make room for registers & psw
 	mvc	SP_PSW(16,%r15),0(%r12)	# move user PSW to stack
-	la	%r12,\psworg
 	stg	%r2,SP_ORIG_R2(%r15)	# store original content of gpr 2
-	icm	%r12,12,__LC_SVC_ILC
+	icm	%r12,3,__LC_SVC_ILC
 	stmg	%r0,%r11,SP_R0(%r15)	# store gprs %r0-%r11 to kernel stack
-	st	%r12,SP_ILC(%r15)
+	st	%r12,SP_SVCNR(%r15)
 	mvc	SP_R12(32,%r15),\savearea # move %r12-%r15 to stack
 	la	%r12,0
 	stg	%r12,__SF_BACKCHAIN(%r15)
···
 #endif
 sysc_do_svc:
 	lg	%r9,__LC_THREAD_INFO	# load pointer to thread_info struct
-	slag	%r7,%r7,2	# *4 and test for svc 0
+	ltgr	%r7,%r7		# test for svc 0
 	jnz	sysc_nr_ok
 	# svc 0: system call number in %r1
 	cl	%r1,BASED(.Lnr_syscalls)
 	jnl	sysc_nr_ok
 	lgfr	%r7,%r1 	# clear high word in r1
-	slag	%r7,%r7,2	# svc 0: system call number in %r1
 sysc_nr_ok:
 	mvc	SP_ARGS(8,%r15),SP_R7(%r15)
 sysc_do_restart:
+	sth	%r7,SP_SVCNR(%r15)
+	sllg	%r7,%r7,2	# svc number * 4
 	larl	%r10,sys_call_table
 #ifdef CONFIG_COMPAT
 	tm	__TI_flags+5(%r9),(_TIF_31BIT>>16)  # running in 31 bit mode ?
···
 sysc_restart:
 	ni	__TI_flags+7(%r9),255-_TIF_RESTART_SVC # clear TIF_RESTART_SVC
 	lg	%r7,SP_R2(%r15)		# load new svc number
-	slag	%r7,%r7,2		# *4
 	mvc	SP_R2(8,%r15),SP_ORIG_R2(%r15) # restore first argument
 	lmg	%r2,%r6,SP_R2(%r15)	# load svc arguments
 	j	sysc_do_restart 	# restart svc
···
 # _TIF_SINGLE_STEP is set, call do_single_step
 #
 sysc_singlestep:
-	ni	__TI_flags+7(%r9),255-_TIF_SINGLE_STEP # clear TIF_SINGLE_STEP
-	lhi	%r0,__LC_PGM_OLD_PSW
-	sth	%r0,SP_TRAP(%r15)	# set trap indication to pgm check
+	ni	__TI_flags+7(%r9),255-_TIF_SINGLE_STEP	# clear TIF_SINGLE_STEP
+	xc	SP_SVCNR(2,%r15),SP_SVCNR(%r15)		# clear svc number
 	la	%r2,SP_PTREGS(%r15)	# address of register-save area
 	larl	%r14,sysc_return	# load adr. of system return
 	jg	do_single_step		# branch to do_sigtrap
···
 	lghi	%r0,NR_syscalls
 	clgr	%r0,%r2
 	jnh	sysc_tracenogo
-	slag	%r7,%r2,2		# *4
+	sllg	%r7,%r2,2		# svc number *4
 	lgf	%r8,0(%r7,%r10)
 sysc_tracego:
 	lmg	%r3,%r6,SP_R3(%r15)
···
 # per was called from kernel, must be kprobes
 #
 kernel_per:
-	lhi	%r0,__LC_PGM_OLD_PSW
-	sth	%r0,SP_TRAP(%r15)	# set trap indication to pgm check
+	xc	SP_SVCNR(2,%r15),SP_SVCNR(%r15)	# clear svc number
 	la	%r2,SP_PTREGS(%r15)	# address of register-save area
 	larl	%r14,sysc_restore	# load adr. of system ret, no work
 	jg	do_single_step		# branch to do_single_step

arch/s390/kernel/ptrace.c

···
 		 * debugger stored an invalid system call number. Skip
 		 * the system call and the system call restart handling.
 		 */
-		regs->trap = -1;
+		regs->svcnr = 0;
 		ret = -1;
 	}
 

arch/s390/kernel/signal.c

···
 	current->thread.fp_regs.fpc &= FPC_VALID_MASK;
 
 	restore_fp_regs(&current->thread.fp_regs);
-	regs->trap = -1;	/* disable syscall checks */
+	regs->svcnr = 0;	/* disable syscall checks */
 	return 0;
 }
 
···
 		oldset = &current->blocked;
 
 	/* Are we from a system call? */
-	if (regs->trap == __LC_SVC_OLD_PSW) {
+	if (regs->svcnr) {
 		continue_addr = regs->psw.addr;
 		restart_addr = continue_addr - regs->ilc;
 		retval = regs->gprs[2];
···
 		case -ERESTART_RESTARTBLOCK:
 			regs->gprs[2] = -EINTR;
 		}
-		regs->trap = -1;	/* Don't deal with this again. */
+		regs->svcnr = 0;	/* Don't deal with this again. */
 	}
 
 	/* Get signal to deliver.  When running under ptrace, at this point