powerpc/ptrace: Preserve previous fprs/vsrs on short regset write

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@arm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
[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@decadent.org.uk>

diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index 5de73db..b7ab4b4 100644 (file)
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -359,6 +359,10 @@ static int fpr_set(struct task_struct *target, const struct user_regset *regset,
        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 *target, const struct user_regset *regset,
 
        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++)