2022-06-01 19:14:39

by Daniel Borkmann

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

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 <[email protected]>
> ---
> 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.

Thanks,
Daniel

2022-06-04 01:56:42

by Andrii Nakryiko

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 <[email protected]> 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 <[email protected]>
> > ---
> > 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