[PATCH] powerpc: Implement PR_[GS]ET_UNALIGN prctls for powerpc

This gives the ability to control whether alignment exceptions get
fixed up or reported to the process as a SIGBUS, using the existing
PR_SET_UNALIGN and PR_GET_UNALIGN prctls.  We do not implement the
option of logging a message on alignment exceptions.

Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 15 insertions, 2 deletions

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 2d35d83961b2..e4732459c485 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -752,6 +752,17 @@ int get_endian(struct task_struct *tsk, unsigned long adr)
         return put_user(val, (unsigned int __user *)adr);
 }
 
+int set_unalign_ctl(struct task_struct *tsk, unsigned int val)
+{
+        tsk->thread.align_ctl = val;
+        return 0;
+}
+
+int get_unalign_ctl(struct task_struct *tsk, unsigned long adr)
+{
+        return put_user(tsk->thread.align_ctl, (unsigned int __user *)adr);
+}
+
 #define TRUNC_PTR(x)    ((typeof(x))(((unsigned long)(x)) & 0xffffffff))
 
 int sys_clone(unsigned long clone_flags, unsigned long usp,
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 03def5715494..91a6e04d9741 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -805,9 +805,11 @@ void __kprobes program_check_exception(struct pt_regs *regs)
 
 void alignment_exception(struct pt_regs *regs)
 {
-        int fixed;
+        int fixed = 0;
 
-        fixed = fix_alignment(regs);
+        /* we don't implement logging of alignment exceptions */
+        if (!(current->thread.align_ctl & PR_UNALIGN_SIGBUS))
+                fixed = fix_alignment(regs);
 
         if (fixed == 1) {
                 regs->nip += 4; /* skip over emulated instruction */