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>

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index 0121d21..c0511c2 100644 (file)
--- 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;
 }