[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 <schwidefsky@de.ibm.com>

2 files changed, 17 insertions, 13 deletions

diff --git a/arch/s390/include/asm/ptrace.h b/arch/s390/include/asm/ptrace.h
index a7226f8..fb0ca47 100644
--- a/arch/s390/include/asm/ptrace.h
+++ b/arch/s390/include/asm/ptrace.h
@@ -321,8 +321,8 @@ struct pt_regs
 	psw_t psw;
 	unsigned long gprs[NUM_GPRS];
 	unsigned long orig_gpr2;
+	unsigned short svcnr;
 	unsigned short ilc;
-	unsigned short trap;
 };
 #endif
 
diff --git a/arch/s390/include/asm/syscall.h b/arch/s390/include/asm/syscall.h
index 6e62397..2429b87 100644
--- a/arch/s390/include/asm/syscall.h
+++ b/arch/s390/include/asm/syscall.h
@@ -17,9 +17,7 @@
 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,
@@ -52,18 +50,20 @@ static inline void syscall_get_arguments(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,
@@ -74,7 +74,11 @@ 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 */