On Thu, Oct 31, 2013 at 01:38:58PM -0500, Tom wrote:
> From: Tom Musta <tommu...@gmail.com>
>
> 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 <tommu...@gmail.com>
> ---
> arch/powerpc/lib/sstep.c | 52 +++++++++++++++++++++++++++++++++++----------
> 1 files changed, 40 insertions(+), 12 deletions(-)
>
> diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
> index c8743e1..1cfd150 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);
This breaks 32-bit big-endian (as well as making the code longer and
more complex).
In fact, to make this work for 64-bit little-endian, all you really
needed to do was ifdef out the statement:
ptr += sizeof(unsigned long) - nb;
Paul.
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
