On Tue, 28 Jul 2015 20:13:41 -0700
Joe Perches <joe@xxxxxxxxxxx> wrote:
> On Tue, 2015-07-28 at 16:09 +0200, Michael Holzheu wrote:
> > The EMIT6_DISP_LH macro passes the "disp" parameter to the _EMIT6_DISP_LH
> > macro. The _EMIT6_DISP_LH macro uses the "disp" parameter twice:
> >
> > unsigned int __disp_h = ((u32)disp) & 0xff000;
> > unsigned int __disp_l = ((u32)disp) & 0x00fff;
> >
> > The EMIT6_DISP_LH is used several times with EMIT_CONST_U64() as "disp"
> > parameter. Therefore always two constants are created per usage of
> > EMIT6_DISP_LH.
> >
> > Fix this and add variable "__disp" to avoid multiple expansions.
> >
> > Fixes: 054623105728 ("s390/bpf: Add s390x eBPF JIT compiler backend")
> > Signed-off-by: Michael Holzheu <holzheu@xxxxxxxxxxxxxxxxxx>
> > ---
> > arch/s390/net/bpf_jit_comp.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
> > index 01ad166..de0f0bc 100644
> > --- a/arch/s390/net/bpf_jit_comp.c
> > +++ b/arch/s390/net/bpf_jit_comp.c
> > @@ -221,8 +221,9 @@ static inline void reg_set_seen(struct nbpf_jit *jit, u32 b1)
> >
> > #define EMIT6_DISP_LH(op1, op2, b1, b2, b3, disp) \
> > ({ \
> > + int __disp = (disp); \
> > _EMIT6_DISP_LH(op1 | reg(b1, b2) << 16 | \
> > - reg_high(b3) << 8, op2, disp); \
> > + reg_high(b3) << 8, op2, __disp); \
> > REG_SET_SEEN(b1); \
> > REG_SET_SEEN(b2); \
> > REG_SET_SEEN(b3); \
>
> Perhaps it'd be better to change _EMIT6_DISP_LH
Looks a bit better. I will send the updated patch.
Thanks!
Michael
> ---
> diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
> index 3a15baa..409e206 100644
> --- a/arch/s390/net/bpf_jit_comp.c
> +++ b/arch/s390/net/bpf_jit_comp.c
> @@ -205,8 +205,9 @@ static inline void reg_set_seen(struct bpf_jit *jit,
> u32 b1)
>
> #define _EMIT6_DISP_LH(op1, op2, disp) \
> ({ \
> - unsigned int __disp_h = ((u32)disp) & 0xff000; \
> - unsigned int __disp_l = ((u32)disp) & 0x00fff; \
> + u32 _disp = (u32)disp; \
> + unsigned int __disp_h = _disp & 0xff000; \
> + unsigned int __disp_l = _disp & 0x00fff; \
> _EMIT6(op1 | __disp_l, op2 | __disp_h >> 4); \
> })
>
>
>
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