On Tue, May 5, 2020 at 5:08 PM Michael Ellerman <m...@ellerman.id.au> wrote: > > Jordan Niethe <jniet...@gmail.com> writes: > > A modulo operation is used for calculating the current offset from a > > breakpoint within the breakpoint table. As instruction lengths are > > always a power of 2, this can be replaced with a bitwise 'and'. The > > current check for word alignment can be replaced with checking that the > > lower 2 bits are not set. > > > > Suggested-by: Christophe Leroy <christophe.le...@c-s.fr> > > Signed-off-by: Jordan Niethe <jniet...@gmail.com> > > --- > > v6: New to series > > --- > > arch/powerpc/xmon/xmon.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c > > index bbfea22f4a96..e122f0c8a044 100644 > > --- a/arch/powerpc/xmon/xmon.c > > +++ b/arch/powerpc/xmon/xmon.c > > @@ -857,8 +857,8 @@ static struct bpt *in_breakpoint_table(unsigned long > > nip, unsigned long *offp) > > off = nip - (unsigned long) bpt_table; > > if (off >= sizeof(bpt_table)) > > return NULL; > > - *offp = off % BPT_SIZE; > > - if (*offp != 0 && *offp != 4) > > + *offp = off & (BPT_SIZE - 1); > > + if (off & 3) > > return NULL; > > It would be even better if you didn't hard code the 3 wouldn't it? > The three is just checking word alignment, which I think was the intention of the previous - if (*offp != 0 && *offp != 4) But using BPT_SIZE is is a different calculation. BPT_SIZE == 2 * sizeof(unsigned int) == 8 Which would mean the trap of the breakpoint pair of instructions would return NULL.
> eg: > > + *offp = off & (BPT_SIZE - 1); > + if (off & (BPT_SIZE - 1)) > return NULL; > > cheers