MIPS: Factor out NT_PRFPREG regset access helpers

In preparation to fix a commit 72b22bbad1e7 ("MIPS: Don't assume 64-bit
FP registers for FP regset") FCSR access regression factor out
NT_PRFPREG regset access helpers for the non-MSA and the MSA variants
respectively, to avoid having to deal with excessive indentation in the
actual fix.

No functional change, however use `target->thread.fpu.fpr[0]' rather
than `target->thread.fpu.fpr[i]' for FGR holding type size determination
as there's no `i' variable to refer to anymore, and for the factored out
`i' variable declaration use `unsigned int' rather than `unsigned' as
its type, following the common style.

Signed-off-by: Maciej W. Rozycki <macro@mips.com>
Fixes: 72b22bbad1e7 ("MIPS: Don't assume 64-bit FP registers for FP regset")
Cc: James Hogan <james.hogan@mips.com>
Cc: Paul Burton <Paul.Burton@mips.com>
Cc: Alex Smith <alex@alex-smith.me.uk>
Cc: Dave Martin <Dave.Martin@arm.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org # v3.15+
Patchwork: https://patchwork.linux-mips.org/patch/17925/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 83 insertions, 25 deletions

diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c
index efbd8df8b665..62e8ffd9370a 100644
--- a/arch/mips/kernel/ptrace.c
+++ b/arch/mips/kernel/ptrace.c
@@ -419,25 +419,36 @@ static int gpr64_set(struct task_struct *target,
 
 #endif /* CONFIG_64BIT */
 
-static int fpr_get(struct task_struct *target,
-                   const struct user_regset *regset,
-                   unsigned int pos, unsigned int count,
-                   void *kbuf, void __user *ubuf)
+/*
+ * Copy the floating-point context to the supplied NT_PRFPREG buffer,
+ * !CONFIG_CPU_HAS_MSA variant.  FP context's general register slots
+ * correspond 1:1 to buffer slots.
+ */
+static int fpr_get_fpa(struct task_struct *target,
+                       unsigned int *pos, unsigned int *count,
+                       void **kbuf, void __user **ubuf)
 {
-        unsigned i;
-        int err;
-        u64 fpr_val;
-
-        /* XXX fcr31  */
+        return user_regset_copyout(pos, count, kbuf, ubuf,
+                                   &target->thread.fpu,
+                                   0, sizeof(elf_fpregset_t));
+}
 
-        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));
+/*
+ * Copy the floating-point context to the supplied NT_PRFPREG buffer,
+ * CONFIG_CPU_HAS_MSA variant.  Only lower 64 bits of FP context's
+ * general register slots are copied to buffer slots.
+ */
+static int fpr_get_msa(struct task_struct *target,
+                       unsigned int *pos, unsigned int *count,
+                       void **kbuf, void __user **ubuf)
+{
+        unsigned int i;
+        u64 fpr_val;
+        int err;
 
         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,
+                err = user_regset_copyout(pos, count, kbuf, ubuf,
                                           &fpr_val, i * sizeof(elf_fpreg_t),
                                           (i + 1) * sizeof(elf_fpreg_t));
                 if (err)
@@ -447,27 +458,54 @@ static int fpr_get(struct task_struct *target,
         return 0;
 }
 
-static int fpr_set(struct task_struct *target,
+/* Copy the floating-point context to the supplied NT_PRFPREG buffer.  */
+static int fpr_get(struct task_struct *target,
                    const struct user_regset *regset,
                    unsigned int pos, unsigned int count,
-                   const void *kbuf, const void __user *ubuf)
+                   void *kbuf, void __user *ubuf)
 {
-        unsigned i;
         int err;
-        u64 fpr_val;
 
         /* XXX fcr31  */
 
-        init_fp_ctx(target);
+        if (sizeof(target->thread.fpu.fpr[0]) == sizeof(elf_fpreg_t))
+                err = fpr_get_fpa(target, &pos, &count, &kbuf, &ubuf);
+        else
+                err = fpr_get_msa(target, &pos, &count, &kbuf, &ubuf);
+
+        return err;
+}
 
-        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));
+/*
+ * Copy the supplied NT_PRFPREG buffer to the floating-point context,
+ * !CONFIG_CPU_HAS_MSA variant.   Buffer slots correspond 1:1 to FP
+ * context's general register slots.
+ */
+static int fpr_set_fpa(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));
+}
+
+/*
+ * Copy the supplied NT_PRFPREG buffer to the floating-point context,
+ * CONFIG_CPU_HAS_MSA variant.  Buffer slots are copied to lower 64
+ * bits only of FP context's general register slots.
+ */
+static int fpr_set_msa(struct task_struct *target,
+                       unsigned int *pos, unsigned int *count,
+                       const void **kbuf, const void __user **ubuf)
+{
+        unsigned int i;
+        u64 fpr_val;
+        int err;
 
         BUILD_BUG_ON(sizeof(fpr_val) != sizeof(elf_fpreg_t));
-        for (i = 0; i < NUM_FPU_REGS && count >= sizeof(elf_fpreg_t); i++) {
-                err = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+        for (i = 0; i < NUM_FPU_REGS && *count >= sizeof(elf_fpreg_t); i++) {
+                err = user_regset_copyin(pos, count, kbuf, ubuf,
                                          &fpr_val, i * sizeof(elf_fpreg_t),
                                          (i + 1) * sizeof(elf_fpreg_t));
                 if (err)
@@ -478,6 +516,26 @@ static int fpr_set(struct task_struct *target,
         return 0;
 }
 
+/* Copy the supplied NT_PRFPREG buffer to the floating-point context.  */
+static int fpr_set(struct task_struct *target,
+                   const struct user_regset *regset,
+                   unsigned int pos, unsigned int count,
+                   const void *kbuf, const void __user *ubuf)
+{
+        int err;
+
+        /* XXX fcr31  */
+
+        init_fp_ctx(target);
+
+        if (sizeof(target->thread.fpu.fpr[0]) == sizeof(elf_fpreg_t))
+                err = fpr_set_fpa(target, &pos, &count, &kbuf, &ubuf);
+        else
+                err = fpr_set_msa(target, &pos, &count, &kbuf, &ubuf);
+
+        return err;
+}
+
 enum mips_regset {
         REGSET_GPR,
         REGSET_FPR,