parisc: fix ptrace breakage

1) PTRACE_SYSCALL doesn't work for 64bit process on parisc64.
Compat syscall table is used instead of 64bit one.  IMO we should either
refuse to allow PTRACE_SYSCALL for 64bit processes or duplicate the
logics choosing the right syscall table into .Ltracesys.

	2) if you have let the tracee run with PTRACE_SYSCALL and
it had stopped, you can use PTRACE_POKEUSR to modify syscall number
(r20) and arguments 1--4 (r26--r23).  Modifications will have effect.
However, modifying arguments 5 and 6 (r22 and r21 resp.) works only
when process (32bit one) runs on 64bit host - on 32bit one it has no
effect.  AFAICS, the diff below should fix that one.

Signed-off-by: Al Viro <viro@ZenIV.linux.org.uk>
Tested-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>

1 files changed, 4 insertions, 1 deletions

diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S
index 86742df0b194..5e055240f00b 100644
--- a/arch/parisc/kernel/syscall.S
+++ b/arch/parisc/kernel/syscall.S
@@ -309,10 +309,13 @@ tracesys_next:
         LDREG   TASK_PT_GR25(%r1), %r25
         LDREG   TASK_PT_GR24(%r1), %r24
         LDREG   TASK_PT_GR23(%r1), %r23
-#ifdef CONFIG_64BIT
         LDREG   TASK_PT_GR22(%r1), %r22
         LDREG   TASK_PT_GR21(%r1), %r21
+#ifdef CONFIG_64BIT
         ldo     -16(%r30),%r29                  /* Reference param save area */
+#else
+        stw     %r22, -52(%r30)                 /* 5th argument */
+        stw     %r21, -56(%r30)                 /* 6th argument */
 #endif
 
         comiclr,>>=     __NR_Linux_syscalls, %r20, %r0