MIPS: Don't assume 64-bit FP registers for FP regset

When we want to access 64-bit FP register values we can only treat
consecutive registers as being consecutive in memory when the width of
an FP register equals 64 bits. This assumption will not remain true once
MSA support is introduced, so provide a code path which copies each 64
bit FP register value in turn when the width of an FP register differs
from 64 bits.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6427/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/ptrace.c

@@ -304,10 +304,27 @@ static int fpr_get(struct task_struct *target,
 		   unsigned int pos, unsigned int count,
 		   void *kbuf, void __user *ubuf)
 {
-	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
-				   &target->thread.fpu,
-				   0, sizeof(elf_fpregset_t));
+	unsigned i;
+	int err;
+	u64 fpr_val;
+
 	/* XXX fcr31  */
+
+	if (sizeof(target->thread.fpu.fpr[i]) == sizeof(elf_fpreg_t))
+		return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+					   &target->thread.fpu,
+					   0, sizeof(elf_fpregset_t));
+
+	for (i = 0; i < NUM_FPU_REGS; i++) {
+		fpr_val = get_fpr64(&target->thread.fpu.fpr[i], 0);
+		err = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+					  &fpr_val, i * sizeof(elf_fpreg_t),
+					  (i + 1) * sizeof(elf_fpreg_t));
+		if (err)
+			return err;
+	}
+
+	return 0;
 }
 
 static int fpr_set(struct task_struct *target,
@@ -315,10 +332,27 @@ static int fpr_set(struct task_struct *target,
 		   unsigned int pos, unsigned int count,
 		   const void *kbuf, const void __user *ubuf)
 {
-	return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
-				  &target->thread.fpu,
-				  0, sizeof(elf_fpregset_t));
+	unsigned i;
+	int err;
+	u64 fpr_val;
+
 	/* XXX fcr31  */
+
+	if (sizeof(target->thread.fpu.fpr[i]) == sizeof(elf_fpreg_t))
+		return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+					  &target->thread.fpu,
+					  0, sizeof(elf_fpregset_t));
+
+	for (i = 0; i < NUM_FPU_REGS; i++) {
+		err = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+					 &fpr_val, i * sizeof(elf_fpreg_t),
+					 (i + 1) * sizeof(elf_fpreg_t));
+		if (err)
+			return err;
+		set_fpr64(&target->thread.fpu.fpr[i], 0, fpr_val);
+	}
+
+	return 0;
 }
 
 enum mips_regset {