[RFC PATCH 3/5] powerpc: Fix pmu get/set functions

[Pedro Franco de Carvalho <pedromfc@linux.vnet.ibm.com>]

The PMU regset exposed through ptrace has 5 64-bit words, which are
all copied in and out. However, mmcr0 in the thread_struct is an
unsigned, which causes pmu_set to clobber the next variable in the
thread_struct (used_ebb), and pmu_get to return the same variable in
one half of the mmcr0 slot.
---
 arch/powerpc/kernel/ptrace.c | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index be8ca03a0bd5..69123feaef9e 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -1733,6 +1733,9 @@ static int pmu_get(struct task_struct *target,
 		      unsigned int pos, unsigned int count,
 		      void *kbuf, void __user *ubuf)
 {
+	int ret = 0;
+	unsigned long mmcr0 = target->thread.mmcr0;
+
 	/* Build tests */
 	BUILD_BUG_ON(TSO(siar) + sizeof(unsigned long) != TSO(sdar));
 	BUILD_BUG_ON(TSO(sdar) + sizeof(unsigned long) != TSO(sier));
@@ -1742,9 +1745,16 @@ static int pmu_get(struct task_struct *target,
 	if (!cpu_has_feature(CPU_FTR_ARCH_207S))
 		return -ENODEV;
 
-	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
-			&target->thread.siar, 0,
+	ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+		&target->thread.siar, 0,
+		4 * sizeof(unsigned long));
+
+	if (!ret)
+		ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+			&mmcr0, 4 * sizeof(unsigned long),
 			5 * sizeof(unsigned long));
+
+	return ret;
 }
 
 static int pmu_set(struct task_struct *target,
@@ -1754,6 +1764,12 @@ static int pmu_set(struct task_struct *target,
 {
 	int ret = 0;
 
+#ifdef __BIG_ENDIAN
+	int mmcr0_offset = sizeof(unsigned);
+#else
+	int mmcr0_offset = 0;
+#endif
+
 	/* Build tests */
 	BUILD_BUG_ON(TSO(siar) + sizeof(unsigned long) != TSO(sdar));
 	BUILD_BUG_ON(TSO(sdar) + sizeof(unsigned long) != TSO(sier));
@@ -1783,9 +1799,16 @@ static int pmu_set(struct task_struct *target,
 			4 * sizeof(unsigned long));
 
 	if (!ret)
+		ret = user_regset_copyin_ignore(&pos, &count, &kbuf,
+			&ubuf, 4 * sizeof(unsigned long),
+			4 * sizeof(unsigned long) + mmcr0_offset);
+
+	if (!ret)
 		ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
-			&target->thread.mmcr0, 4 * sizeof(unsigned long),
-			5 * sizeof(unsigned long));
+			&target->thread.mmcr0,
+			4 * sizeof(unsigned long) + mmcr0_offset,
+			4 * sizeof(unsigned long) + mmcr0_offset
+			+ sizeof (unsigned));
 	return ret;
 }
 #endif
-- 
2.13.6