[PATCH v2] Alpha: unbreak osf_setsysinfo(SSI_NVPAIRS, [SSIN_UACPROC, UAC_SIGBUS])

The bug was accidentally found by the following program:
   #include <asm/sysinfo.h>
   #include <asm/unistd.h>
   #include <sys/syscall.h>
   static int setsysinfo(unsigned long op, void *buffer, unsigned long size,
                         int *start, void *arg, unsigned long flag) {
       return syscall(__NR_osf_setsysinfo, op, buffer, size, start, arg, flag);
   }

   int main(int argc, char **argv) {
       short x[10];
       unsigned int buf[2] = { SSIN_UACPROC, UAC_SIGBUS, };
       setsysinfo(SSI_NVPAIRS, buf, 1, 0, 0, 0);

       int  *y = (int*) (x+1);
       *y = 0;
       return 0;
   }

The program shoud fail on SIGBUS, but didn't.

The patch is a second part of userspace flag fix:

quoted

commit 745dd2405e281d96c0a449103bdf6a895048f28c
Author: Michael Cree [off-list ref]
Date:   Mon Nov 30 22:44:40 2009 -0500

   Alpha: Rearrange thread info flags fixing two regressions

   Both regressions fixed by (1) rearranging TIF_NOTIFY_RESUME flag to be
   in lower 8 bits of the thread info flags, and (2) making sure that
   ALPHA_UAC_SHIFT matches the rearrangement of the thread info flags.

Deleted outdated out-of-sync 'UAC_SHIFT' (the cause of bug) in favour of 'ALPHA_UAC_SHIFT'.

Signed-off-by: Sergei Trofimovich <redacted>
Cc: linux-alpha@vger.kernel.org
Cc: Michael Cree <redacted>
Cc: Richard Henderson <redacted>
Cc: Ivan Kokshaysky <redacted>
Cc: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/include/asm/sysinfo.h     |    9 ---------
 arch/alpha/include/asm/thread_info.h |    8 ++++----
 arch/alpha/kernel/osf_sys.c          |    7 ++++---
 3 files changed, 8 insertions(+), 16 deletions(-)

diff --git a/arch/alpha/include/asm/sysinfo.h b/arch/alpha/include/asm/sysinfo.h
index 086aba2..e77d77c 100644
--- a/arch/alpha/include/asm/sysinfo.h
+++ b/arch/alpha/include/asm/sysinfo.h

@@ -27,13 +27,4 @@

 #define UAC_NOFIX                      2
 #define UAC_SIGBUS                     4

-
-#ifdef __KERNEL__
-
-/* This is the shift that is applied to the UAC bits as stored in the
-   per-thread flags.  See thread_info.h.  */
-#define UAC_SHIFT                      6
-
-#endif
-
 #endif /* __ASM_ALPHA_SYSINFO_H */

diff --git a/arch/alpha/include/asm/thread_info.h b/arch/alpha/include/asm/thread_info.h
index 6f32f9c..ff73db0 100644
--- a/arch/alpha/include/asm/thread_info.h
+++ b/arch/alpha/include/asm/thread_info.h

@@ -74,9 +74,9 @@ register struct thread_info *__current_thread_info __asm__("$8");

 #define TIF_NEED_RESCHED       3       /* rescheduling necessary */
 #define TIF_POLLING_NRFLAG     8       /* poll_idle is polling NEED_RESCHED */
 #define TIF_DIE_IF_KERNEL      9       /* dik recursion lock */
-#define TIF_UAC_NOPRINT                10      /* see sysinfo.h */
-#define TIF_UAC_NOFIX          11
-#define TIF_UAC_SIGBUS         12
+#define TIF_UAC_NOPRINT                10      /* ! Preserve sequence of following */
+#define TIF_UAC_NOFIX          11      /* ! flags as they match            */
+#define TIF_UAC_SIGBUS         12      /* ! userspace part of 'osf_sysinfo' */
 #define TIF_MEMDIE             13      /* is terminating due to OOM killer */
 #define TIF_RESTORE_SIGMASK    14      /* restore signal mask in do_signal */
 #define TIF_FREEZE             16      /* is freezing for suspend */

@@ -97,7 +97,7 @@ register struct thread_info *__current_thread_info __asm__("$8");

 #define _TIF_ALLWORK_MASK      (_TIF_WORK_MASK         \
                                | _TIF_SYSCALL_TRACE)

-#define ALPHA_UAC_SHIFT                10
+#define ALPHA_UAC_SHIFT                TIF_UAC_NOPRINT
 #define ALPHA_UAC_MASK         (1 << TIF_UAC_NOPRINT | 1 << TIF_UAC_NOFIX | \
                                1 << TIF_UAC_SIGBUS)

diff --git a/arch/alpha/kernel/osf_sys.c b/arch/alpha/kernel/osf_sys.c
index 326f0a2..2032f67 100644
--- a/arch/alpha/kernel/osf_sys.c
+++ b/arch/alpha/kernel/osf_sys.c

@@ -42,6 +42,7 @@

 #include <asm/uaccess.h>
 #include <asm/system.h>
 #include <asm/sysinfo.h>
+#include <asm/thread_info.h>
 #include <asm/hwrpb.h>
 #include <asm/processor.h>

@@ -633,7 +634,7 @@ SYSCALL_DEFINE5(osf_getsysinfo, unsigned long, op, void __user *, buffer,

       case GSI_UACPROC:
               if (nbytes < sizeof(unsigned int))
                       return -EINVAL;
-               w = (current_thread_info()->flags >> UAC_SHIFT) & UAC_BITMASK;
+               w = (current_thread_info()->flags >> ALPHA_UAC_SHIFT) & UAC_BITMASK;
               if (put_user(w, (unsigned int __user *)buffer))
                       return -EFAULT;
               return 1;

@@ -756,8 +757,8 @@ SYSCALL_DEFINE5(osf_setsysinfo, unsigned long, op, void __user *, buffer,

                       case SSIN_UACPROC:
                       again:
                               old = current_thread_info()->flags;
-                               new = old & ~(UAC_BITMASK << UAC_SHIFT);
-                               new = new | (w & UAC_BITMASK) << UAC_SHIFT;
+                               new = old & ~(UAC_BITMASK << ALPHA_UAC_SHIFT);
+                               new = new | (w & UAC_BITMASK) << ALPHA_UAC_SHIFT;
                               if (cmpxchg(&current_thread_info()->flags,
                                           old, new) != old)
                                       goto again;
--
1.7.3.4