powerpc: Add VSX context save/restore, ptrace and signal support

This patch extends the floating point save and restore code to use the
VSX load/stores when VSX is available.  This will make FP context
save/restore marginally slower on FP only code, when VSX is available,
as it has to load/store 128bits rather than just 64bits.

Mixing FP, VMX and VSX code will get constant architected state.

The signals interface is extended to enable access to VSR 0-31
doubleword 1 after discussions with tool chain maintainers.  Backward
compatibility is maintained.

The ptrace interface is also extended to allow access to VSR 0-31 full
registers.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index f7fa395b9fb5..349d3487d920 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -378,6 +378,21 @@ static int save_user_regs(struct pt_regs *regs, struct mcontext __user *frame,
         memcpy(&buf[i], &current->thread.fpscr, sizeof(double));
         if (__copy_to_user(&frame->mc_fregs, buf, ELF_NFPREG * sizeof(double)))
                 return 1;
+        /*
+         * Copy VSR 0-31 upper half from thread_struct to local
+         * buffer, then write that to userspace.  Also set MSR_VSX in
+         * the saved MSR value to indicate that frame->mc_vregs
+         * contains valid data
+         */
+        if (current->thread.used_vsr) {
+                flush_vsx_to_thread(current);
+                for (i = 0; i < 32 ; i++)
+                        buf[i] = current->thread.fpr[i][TS_VSRLOWOFFSET];
+                if (__copy_to_user(&frame->mc_vsregs, buf,
+                                   ELF_NVSRHALFREG  * sizeof(double)))
+                        return 1;
+                msr |= MSR_VSX;
+        }
 #else
         /* save floating-point registers */
         if (__copy_to_user(&frame->mc_fregs, current->thread.fpr,
@@ -482,6 +497,24 @@ static long restore_user_regs(struct pt_regs *regs,
         for (i = 0; i < 32 ; i++)
                 current->thread.TS_FPR(i) = buf[i];
         memcpy(&current->thread.fpscr, &buf[i], sizeof(double));
+        /*
+         * Force the process to reload the VSX registers from
+         * current->thread when it next does VSX instruction.
+         */
+        regs->msr &= ~MSR_VSX;
+        if (msr & MSR_VSX) {
+                /*
+                 * Restore altivec registers from the stack to a local
+                 * buffer, then write this out to the thread_struct
+                 */
+                if (__copy_from_user(buf, &sr->mc_vsregs,
+                                     sizeof(sr->mc_vsregs)))
+                        return 1;
+                for (i = 0; i < 32 ; i++)
+                        current->thread.fpr[i][TS_VSRLOWOFFSET] = buf[i];
+        } else if (current->thread.used_vsr)
+                for (i = 0; i < 32 ; i++)
+                        current->thread.fpr[i][TS_VSRLOWOFFSET] = 0;
 #else
         if (__copy_from_user(current->thread.fpr, &sr->mc_fregs,
                              sizeof(sr->mc_fregs)))