From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sergei Trofimovich <slyich@gmail.com>
Subject: Re: [PATCH] Alpha: unbreak osf_setsysinfo(SSI_NVPAIRS,
 [SSIN_UACPROC, UAC_SIGBUS])
Date: Sat, 13 Aug 2011 00:51:28 +0300
Message-ID: <20110813005128.7644d5e4@sf.home>
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Cc: Michael Cree <mcree@orcon.net.nz>, rth@twiddle.net, ink@jurassic.park.msu.ru, mattst88@gmail.com

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> I'll build alpha toolchain / qemu root and will try to cook
> nicer patch with compile-time safety checks.

Sent reworked patch: http://marc.info/?l=3Dlinux-alpha&m=3D131318270531656&=
w=3D2

Yelling at the header I've found minor nit:
...
#define SET_UNALIGN_CTL(task,value)     ({                                 =
  \
        task_thread_info(task)->flags =3D ((task_thread_info(task)->flags &=
    \
                ~ALPHA_UAC_MASK)
                | (((value) << ALPHA_UAC_SHIFT)       & (1<<TIF_UAC_NOPRINT=
))\
                | (((value) << (ALPHA_UAC_SHIFT + 1)) & (1<<TIF_UAC_SIGBUS)=
) \
                | (((value) << (ALPHA_UAC_SHIFT - 1)) & (1<<TIF_UAC_NOFIX))=
);\
        0; })

#define GET_UNALIGN_CTL(task,value)     ({                              \
        put_user((task_thread_info(task)->flags & (1 << TIF_UAC_NOPRINT))\
                  >> ALPHA_UAC_SHIFT                                    \
                 | (task_thread_info(task)->flags & (1 << TIF_UAC_SIGBUS))\
                 >> (ALPHA_UAC_SHIFT + 1)                               \
                 | (task_thread_info(task)->flags & (1 << TIF_UAC_NOFIX))\
                 >> (ALPHA_UAC_SHIFT - 1),                              \
                 (int __user *)(value));                                \
        })

The macros SET_UNALIGN_CTL/GET_UNALIGN_CTL are used
only in kernel/sys.c:prctl syscall.

> | (((value) << ALPHA_UAC_SHIFT)       & (1<<TIF_UAC_NOPRINT))
prctl.h: # define PR_UNALIGN_NOPRINT     1

> |  (((value) << (ALPHA_UAC_SHIFT + 1)) & (1<<TIF_UAC_SIGBUS))
prctl.h: # define PR_UNALIGN_SIGBUS      2

> | (((value) << (ALPHA_UAC_SHIFT - 1)) & (1<<TIF_UAC_NOFIX)));

prctl.h: no '4' value

Do you think it's worth adding to userspace interface
or should one just remove it from handled by prctl flags [ABI change]?

Thanks!

diff --git a/include/linux/prctl.h b/include/linux/prctl.h
index a3baeb2..f66539a 100644
--- a/include/linux/prctl.h
+++ b/include/linux/prctl.h
@@ -15,6 +15,7 @@
 #define PR_SET_UNALIGN   6
 # define PR_UNALIGN_NOPRINT    1       /* silently fix up unaligned user a=
ccesses */
 # define PR_UNALIGN_SIGBUS     2       /* generate SIGBUS on unaligned use=
r access */
+# define PR_UNALIGN_NOFIX      4       /* skip offending instruction and d=
o nothing */

 /* Get/set whether or not to drop capabilities on setuid() away from
  * uid 0 (as per security/commoncap.c) */

--=20

  Sergei

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