powerpc/ptrace: Fix bug in signal handling

powerpc/ptrace: Fix bug in signal handling

[Michael Wolf]

In some cases during a threaded core dump not all 
the threads will have a full register set.  This
will cause problems when the sigkill is sent to
the thread
        
Signed-off-by: Mike Wolf <mjw@linux.vnet.ibm.com>
-------

--- ptrace-signal.orig/arch/powerpc/kernel/ptrace.c	2011-02-20 12:15:57.000000000 -0600
+++ ptrace-signal/arch/powerpc/kernel/ptrace.c	2011-02-21 12:39:17.000000000 -0600
@@ -234,11 +234,23 @@
 	if (target->thread.regs == NULL)
 		return -EIO;
 
-	CHECK_FULL_REGS(target->thread.regs);
 
-	ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
-				  target->thread.regs,
-				  0, offsetof(struct pt_regs, msr));
+	if (!FULL_REGS(target->thread.regs)) {
+		ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+					  target->thread.regs,
+					  0, sizeof(long)*PT_R14);
+		if (!ret)
+			ret = user_regset_copyout_poison(&pos, &count, &kbuf, &ubuf,
+						  sizeof(long)*PT_R14, offsetof(struct pt_regs, nip));
+		if (!ret)
+			ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+						  target->thread.regs,
+						  offsetof(struct pt_regs, nip), offsetof(struct pt_regs, msr));
+		
+	} else 
+		ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+					  target->thread.regs,
+					  0, offsetof(struct pt_regs, msr));
 	if (!ret) {
 		unsigned long msr = get_user_msr(target);
 		ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, &msr,
@@ -645,11 +657,24 @@
 	if (target->thread.regs == NULL)
 		return -EIO;
 
-	CHECK_FULL_REGS(target->thread.regs);
-
 	pos /= sizeof(reg);
 	count /= sizeof(reg);
 
+	if(!FULL_REGS(target->thread.regs)) {
+		if (kbuf) {
+			for (; count > 0 && pos < PT_R14; --count)
+				*k++ = regs[pos++];
+			for (; count > 0 && pos < PT_R31; --count,pos++)
+				*k++ = 0xdeadbeef;
+		} else { 
+			for (; count > 0 && pos < PT_R14; --count)
+				if (__put_user((compat_ulong_t) regs[pos++], u++))
+					return -EFAULT;
+			for (; count > 0 && pos < PT_R31; --count,pos++)
+				if (__put_user((compat_ulong_t) 0xdeadbeef, u++))
+					return -EFAULT;
+		}
+	}
 	if (kbuf)
 		for (; count > 0 && pos < PT_MSR; --count)
 			*k++ = regs[pos++];
--- ptrace-signal.orig/include/linux/regset.h	2011-02-20 12:15:57.000000000 -0600
+++ ptrace-signal/include/linux/regset.h	2011-02-21 12:39:17.000000000 -0600
@@ -240,6 +240,32 @@
 	}
 	return 0;
 }
+static inline int user_regset_copyout_poison(unsigned int *pos,
+					   unsigned int *count,
+					   void **kbuf, void __user **ubuf,
+					   const int start_pos,
+					   const int end_pos)
+{
+	long poison_data[17] = { [0 ... 16] = 0xdeadbeefdeadbeefUL };
+
+	if (*count == 0)
+		return 0;
+	BUG_ON(*pos < start_pos);
+	if (end_pos < 0 || *pos < end_pos) {
+		unsigned int copy = (end_pos < 0 ? *count
+				     : min(*count, end_pos - *pos));
+		if (*kbuf) {
+			memset(*kbuf, 0xdeadbeef, copy);
+			*kbuf += copy;
+		} else if (__copy_to_user(*ubuf,poison_data, copy))
+			return -EFAULT;
+		else
+			*ubuf += copy;
+		*pos += copy;
+		*count -= copy;
+	}
+	return 0;
+}
 
 static inline int user_regset_copyin(unsigned int *pos, unsigned int *count,
 				     const void **kbuf,

Re: powerpc/ptrace: Fix bug in signal handling

[Michael Neuling]

Mike,

> Subject: powerpc/ptrace: Fix bug in signal handling

Maybe something more descriptive here like:
  powerpc/ptrace: remove BUG_ON when full register set not available

> In some cases during a threaded core dump not all 
> the threads will have a full register set.  This
> will cause problems when the sigkill is sent to
> the thread

Please add a description for how you are solving this.  Something like
"Solve this by putting poison values in the registers".  Similar inline
comments would be good too.

Also, I'm not convinced this is the right solution... not that I have a
have a better one to suggest :-)

<snip>

> +static inline int user_regset_copyout_poison(unsigned int *pos,
> +					   unsigned int *count,
> +					   void **kbuf, void __user **ubuf,
> +					   const int start_pos,
> +					   const int end_pos)
> +{
> +	long poison_data[17] = { [0 ... 16] = 0xdeadbeefdeadbeefUL };

Why only poison 17 registers?

Mikey