Re: [PATCH bpf-next 5/5] selftests/bpf: Remove the casting about jited_ksyms and jited_linfo

[Pu Lehui]

On 2022/7/17 9:46, Yonghong Song wrote:
> On 7/16/22 5:51 AM, Pu Lehui wrote:
> > We have unified data extension operation of jited_ksyms and jited_linfo
> > into zero extension, so there's no need to cast u64 memory address to
> > long data type.
>
> For subject, we are not 'Remove the casting ...'. What the code did is
> to change the casting.
>
> Also, I don't understand the above commit message. What does this mean
> about 'data extension operation of jited_ksyms and jited_linfo into zero 
> extension'?
>
> In prog_tests/btf.c, we have a few other places to cast 
> jited_linfo[...]/jited_ksyms[...] to 'long' type. Maybe casting
> to 'unsigned long' is a better choice. Casting to 'unsigned long long'
> of course will work, but is it necessary? Or you are talking about
> 64bit kernel and 32bit user space?

Hi Yonghong,

Thanks for your review. We introduced riscv jited line info in series 
[0], and we found that 32-bit systems can not display bpf line info due 
to the inconsistent data extension between jited_ksyms and jited_linfo. 
And we finally unify them to zero extension. By the way, we cleanup the 
related code. jited_ksyms and jited_linfo both are u64 address, no need 
to casting to long, and we previously remove it. But u64 in some arch is 
%ld, so to avoid compiler warnings we just cast to unsigned long long.

And sorry for not updating the subject and comment. I will corret it.

[0] 
https://lore.kernel.org/bpf/CAEf4Bza4RT=KFhr9ev29967dyT0eF_+6ZRqK35beUvnA_NbcqQ@xxxxxxxxxxxxxx/

> > Signed-off-by: Pu Lehui <pulehui@xxxxxxxxxx>
> > ---
> >   tools/testing/selftests/bpf/prog_tests/btf.c | 16 +++++++++-------
> >   1 file changed, 9 insertions(+), 7 deletions(-)
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/btf.c 
> > b/tools/testing/selftests/bpf/prog_tests/btf.c
> > index e852a9df779d..db10fa1745d1 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/btf.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/btf.c
> > @@ -6613,8 +6613,9 @@ static int test_get_linfo(const struct 
> > prog_info_raw_test *test,
> >       }
> >       if (CHECK(jited_linfo[0] != jited_ksyms[0],
> > -          "jited_linfo[0]:%lx != jited_ksyms[0]:%lx",
> > -          (long)(jited_linfo[0]), (long)(jited_ksyms[0]))) {
> > +          "jited_linfo[0]:%llx != jited_ksyms[0]:%llx",
> > +          (unsigned long long)(jited_linfo[0]),
> > +          (unsigned long long)(jited_ksyms[0]))) {
> >           err = -1;
> >           goto done;
> >       }
> > @@ -6632,16 +6633,17 @@ static int test_get_linfo(const struct 
> > prog_info_raw_test *test,
> >           }
> >           if (CHECK(jited_linfo[i] <= jited_linfo[i - 1],
> > -              "jited_linfo[%u]:%lx <= jited_linfo[%u]:%lx",
> > -              i, (long)jited_linfo[i],
> > -              i - 1, (long)(jited_linfo[i - 1]))) {
> > +              "jited_linfo[%u]:%llx <= jited_linfo[%u]:%llx",
> > +              i, (unsigned long long)jited_linfo[i],
> > +              i - 1, (unsigned long long)(jited_linfo[i - 1]))) {
> >               err = -1;
> >               goto done;
> >           }
> >           if (CHECK(jited_linfo[i] - cur_func_ksyms > cur_func_len,
> > -              "jited_linfo[%u]:%lx - %lx > %u",
> > -              i, (long)jited_linfo[i], (long)cur_func_ksyms,
> > +              "jited_linfo[%u]:%llx - %llx > %u",
> > +              i, (unsigned long long)jited_linfo[i],
> > +              (unsigned long long)cur_func_ksyms,
> >                 cur_func_len)) {
> >               err = -1;
> >               goto done;
> .