[PATCH 3.2 120/199] powerpc/ptrace: Preserve previous fprs/vsrs on short regset write

[Ben Hutchings]

3.2.87-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Dave Martin <Dave.Martin@xxxxxxx>

commit 99dfe80a2a246c600440a815741fd2e74a8b4977 upstream.

Ensure that if userspace supplies insufficient data to PTRACE_SETREGSET
to fill all the registers, the thread's old registers are preserved.

Fixes: c6e6771b87d4 ("powerpc: Introduce VSX thread_struct and CONFIG_VSX")
Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
[bwh: Backported to 3.2:
 - fpscr and fpr are direct members of struct thread_struct
 - Use memcpy() for fpscr, like the reverse copy below, to avoid type error
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 arch/powerpc/kernel/ptrace.c | 7 +++++++
 1 file changed, 7 insertions(+)

--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -359,6 +359,10 @@ static int fpr_set(struct task_struct *t
 	flush_fp_to_thread(target);
 
 #ifdef CONFIG_VSX
+	for (i = 0; i < 32 ; i++)
+		buf[i] = target->thread.TS_FPR(i);
+	memcpy(&buf[32], &target->thread.fpscr, sizeof(double));
+
 	/* copy to local buffer then write that out */
 	i = user_regset_copyin(&pos, &count, &kbuf, &ubuf, buf, 0, -1);
 	if (i)
@@ -501,6 +505,9 @@ static int vsr_set(struct task_struct *t
 
 	flush_vsx_to_thread(target);
 
+	for (i = 0; i < 32 ; i++)
+		buf[i] = target->thread.fpr[i][TS_VSRLOWOFFSET];
+
 	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 				 buf, 0, 32 * sizeof(double));
 	for (i = 0; i < 32 ; i++)