linux-kernel - Re: [PATCH bpf-next v3 4/6] libbpf: Unify memory address casting operation style

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Message-ID: <CAEf4BzacrRNDDYFR_4GH40+wxff=hCiyxymig6N+NVrM537AAA@mail.gmail.com>
Date:   Fri, 3 Jun 2022 14:03:06 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Pu Lehui <pulehui@...wei.com>, bpf <bpf@...r.kernel.org>,
        linux-riscv@...ts.infradead.org,
        Networking <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Björn Töpel <bjorn@...nel.org>,
        Luke Nelson <luke.r.nels@...il.com>,
        Xi Wang <xi.wang@...il.com>, Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>
Subject: Re: [PATCH bpf-next v3 4/6] libbpf: Unify memory address casting
 operation style

On Mon, May 30, 2022 at 2:03 PM Daniel Borkmann <daniel@...earbox.net> wrote:
>
> On 5/30/22 11:28 AM, Pu Lehui wrote:
> > The members of bpf_prog_info, which are line_info, jited_line_info,
> > jited_ksyms and jited_func_lens, store u64 address pointed to the
> > corresponding memory regions. Memory addresses are conceptually
> > unsigned, (unsigned long) casting makes more sense, so let's make
> > a change for conceptual uniformity.
> >
> > Signed-off-by: Pu Lehui <pulehui@...wei.com>
> > ---
> >   tools/lib/bpf/bpf_prog_linfo.c | 9 +++++----
> >   1 file changed, 5 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/lib/bpf/bpf_prog_linfo.c b/tools/lib/bpf/bpf_prog_linfo.c
> > index 5c503096ef43..7beb060d0671 100644
> > --- a/tools/lib/bpf/bpf_prog_linfo.c
> > +++ b/tools/lib/bpf/bpf_prog_linfo.c
> > @@ -127,7 +127,8 @@ struct bpf_prog_linfo *bpf_prog_linfo__new(const struct bpf_prog_info *info)
> >       prog_linfo->raw_linfo = malloc(data_sz);
> >       if (!prog_linfo->raw_linfo)
> >               goto err_free;
> > -     memcpy(prog_linfo->raw_linfo, (void *)(long)info->line_info, data_sz);
> > +     memcpy(prog_linfo->raw_linfo, (void *)(unsigned long)info->line_info,
> > +            data_sz);
>
> Took in patch 1-3, lgtm, thanks! My question around the cleanups in patch 4-6 ...
> there are various other such cases e.g. in libbpf, perhaps makes sense to clean all
> of them up at once and not just the 4 locations in here.

if (void *)(long) pattern is wrong, then I guess the best replacement
should be (void *)(uintptr_t) ?

>
> Thanks,
> Daniel