powerpc: Fix Unaligned LE Floating Point Loads and Stores

This patch addresses unaligned single precision floating point loads
and stores in the single-step code.  The old implementation
improperly treated an 8 byte structure as an array of two 4 byte
words, which is a classic little endian bug.

Signed-off-by: Tom Musta <tmusta@gmail.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 40 insertions, 12 deletions

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index 0121d2140ab9..c0511c27a733 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -355,22 +355,36 @@ static int __kprobes do_fp_load(int rn, int (*func)(int, unsigned long),
                                 struct pt_regs *regs)
 {
         int err;
-        unsigned long val[sizeof(double) / sizeof(long)];
+        union {
+                double dbl;
+                unsigned long ul[2];
+                struct {
+#ifdef __BIG_ENDIAN__
+                        unsigned _pad_;
+                        unsigned word;
+#endif
+#ifdef __LITTLE_ENDIAN__
+                        unsigned word;
+                        unsigned _pad_;
+#endif
+                } single;
+        } data;
         unsigned long ptr;
 
         if (!address_ok(regs, ea, nb))
                 return -EFAULT;
         if ((ea & 3) == 0)
                 return (*func)(rn, ea);
-        ptr = (unsigned long) &val[0];
+        ptr = (unsigned long) &data.ul;
         if (sizeof(unsigned long) == 8 || nb == 4) {
-                err = read_mem_unaligned(&val[0], ea, nb, regs);
-                ptr += sizeof(unsigned long) - nb;
+                err = read_mem_unaligned(&data.ul[0], ea, nb, regs);
+                if (nb == 4)
+                        ptr = (unsigned long)&(data.single.word);
         } else {
                 /* reading a double on 32-bit */
-                err = read_mem_unaligned(&val[0], ea, 4, regs);
+                err = read_mem_unaligned(&data.ul[0], ea, 4, regs);
                 if (!err)
-                        err = read_mem_unaligned(&val[1], ea + 4, 4, regs);
+                        err = read_mem_unaligned(&data.ul[1], ea + 4, 4, regs);
         }
         if (err)
                 return err;
@@ -382,28 +396,42 @@ static int __kprobes do_fp_store(int rn, int (*func)(int, unsigned long),
                                  struct pt_regs *regs)
 {
         int err;
-        unsigned long val[sizeof(double) / sizeof(long)];
+        union {
+                double dbl;
+                unsigned long ul[2];
+                struct {
+#ifdef __BIG_ENDIAN__
+                        unsigned _pad_;
+                        unsigned word;
+#endif
+#ifdef __LITTLE_ENDIAN__
+                        unsigned word;
+                        unsigned _pad_;
+#endif
+                } single;
+        } data;
         unsigned long ptr;
 
         if (!address_ok(regs, ea, nb))
                 return -EFAULT;
         if ((ea & 3) == 0)
                 return (*func)(rn, ea);
-        ptr = (unsigned long) &val[0];
+        ptr = (unsigned long) &data.ul[0];
         if (sizeof(unsigned long) == 8 || nb == 4) {
-                ptr += sizeof(unsigned long) - nb;
+                if (nb == 4)
+                        ptr = (unsigned long)&(data.single.word);
                 err = (*func)(rn, ptr);
                 if (err)
                         return err;
-                err = write_mem_unaligned(val[0], ea, nb, regs);
+                err = write_mem_unaligned(data.ul[0], ea, nb, regs);
         } else {
                 /* writing a double on 32-bit */
                 err = (*func)(rn, ptr);
                 if (err)
                         return err;
-                err = write_mem_unaligned(val[0], ea, 4, regs);
+                err = write_mem_unaligned(data.ul[0], ea, 4, regs);
                 if (!err)
-                        err = write_mem_unaligned(val[1], ea + 4, 4, regs);
+                        err = write_mem_unaligned(data.ul[1], ea + 4, 4, regs);
         }
         return err;
 }