On Wed, Dec 11, 2013 at 02:54:40PM +1100, Paul Mackerras wrote: > 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).
And in fact none of this code will get executed in little-endian mode anyway, since we still have this in the middle of emulate_step(): /* * Following cases are for loads and stores, so bail out * if we're in little-endian mode. */ if (regs->msr & MSR_LE) return 0; Paul. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev