powerpc: Handle VSX alignment faults correctly in little-endian mode

This patch fixes the handling of VSX alignment faults in little-endian
mode (the current code assumes the processor is in big-endian mode).

The patch also makes the handlers clear the top 8 bytes of the register
when handling an 8 byte VSX load.

This is based on 2.6.32.

Signed-off-by: Neil Campbell <neilc@linux.vnet.ibm.com>
Cc: <stable@kernel.org>
Acked-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 46 insertions, 17 deletions

diff --git a/arch/powerpc/kernel/align.c b/arch/powerpc/kernel/align.c
index 3839839f83c7..b876e989220b 100644
--- a/arch/powerpc/kernel/align.c
+++ b/arch/powerpc/kernel/align.c
@@ -642,10 +642,14 @@ static int emulate_spe(struct pt_regs *regs, unsigned int reg,
  */
 static int emulate_vsx(unsigned char __user *addr, unsigned int reg,
                        unsigned int areg, struct pt_regs *regs,
-                       unsigned int flags, unsigned int length)
+                       unsigned int flags, unsigned int length,
+                       unsigned int elsize)
 {
         char *ptr;
+        unsigned long *lptr;
         int ret = 0;
+        int sw = 0;
+        int i, j;
 
         flush_vsx_to_thread(current);
 
@@ -654,19 +658,35 @@ static int emulate_vsx(unsigned char __user *addr, unsigned int reg,
         else
                 ptr = (char *) &current->thread.vr[reg - 32];
 
-        if (flags & ST)
-                ret = __copy_to_user(addr, ptr, length);
-        else {
-                if (flags & SPLT){
-                        ret = __copy_from_user(ptr, addr, length);
-                        ptr += length;
+        lptr = (unsigned long *) ptr;
+
+        if (flags & SW)
+                sw = elsize-1;
+
+        for (j = 0; j < length; j += elsize) {
+                for (i = 0; i < elsize; ++i) {
+                        if (flags & ST)
+                                ret |= __put_user(ptr[i^sw], addr + i);
+                        else
+                                ret |= __get_user(ptr[i^sw], addr + i);
                 }
-                ret |= __copy_from_user(ptr, addr, length);
+                ptr  += elsize;
+                addr += elsize;
         }
-        if (flags & U)
-                regs->gpr[areg] = regs->dar;
-        if (ret)
+
+        if (!ret) {
+                if (flags & U)
+                        regs->gpr[areg] = regs->dar;
+
+                /* Splat load copies the same data to top and bottom 8 bytes */
+                if (flags & SPLT)
+                        lptr[1] = lptr[0];
+                /* For 8 byte loads, zero the top 8 bytes */
+                else if (!(flags & ST) && (8 == length))
+                        lptr[1] = 0;
+        } else
                 return -EFAULT;
+
         return 1;
 }
 #endif
@@ -767,16 +787,25 @@ int fix_alignment(struct pt_regs *regs)
 
 #ifdef CONFIG_VSX
         if ((instruction & 0xfc00003e) == 0x7c000018) {
-                /* Additional register addressing bit (64 VSX vs 32 FPR/GPR */
+                unsigned int elsize;
+
+                /* Additional register addressing bit (64 VSX vs 32 FPR/GPR) */
                 reg |= (instruction & 0x1) << 5;
                 /* Simple inline decoder instead of a table */
+                /* VSX has only 8 and 16 byte memory accesses */
+                nb = 8;
                 if (instruction & 0x200)
                         nb = 16;
-                else if (instruction & 0x080)
-                        nb = 8;
-                else
-                        nb = 4;
+
+                /* Vector stores in little-endian mode swap individual
+                   elements, so process them separately */
+                elsize = 4;
+                if (instruction & 0x80)
+                        elsize = 8;
+
                 flags = 0;
+                if (regs->msr & MSR_LE)
+                        flags |= SW;
                 if (instruction & 0x100)
                         flags |= ST;
                 if (instruction & 0x040)
@@ -787,7 +816,7 @@ int fix_alignment(struct pt_regs *regs)
                         nb = 8;
                 }
                 PPC_WARN_ALIGNMENT(vsx, regs);
-                return emulate_vsx(addr, reg, areg, regs, flags, nb);
+                return emulate_vsx(addr, reg, areg, regs, flags, nb, elsize);
         }
 #endif
         /* A size of 0 indicates an instruction we don't support, with