[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 a7226f8143fb..fb0ca4796d3b 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 6e623971fbb9..2429b87eb28d 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 */