linux-kernel - Re: [PATCH] kallsyms: remove unused arch_get

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Message-ID: <ZHDuxYBsaGn7xJBn@bombadil.infradead.org>
Date:   Fri, 26 May 2023 10:39:17 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Alan Maguire <alan.maguire@...cle.com>
Cc:     Arnd Bergmann <arnd@...db.de>, Song Liu <song@...nel.org>,
        Arnd Bergmann <arnd@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...e.de>, linux-modules@...r.kernel.org,
        Zhen Lei <thunder.leizhen@...wei.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] kallsyms: remove unused arch_get_kallsym() helper

On Fri, May 26, 2023 at 03:39:22PM +0100, Alan Maguire wrote:
> On 26/05/2023 07:41, Arnd Bergmann wrote:
> > On Fri, May 26, 2023, at 05:24, Luis Chamberlain wrote:
> >> On Thu, May 25, 2023 at 06:45:35PM -0700, Song Liu wrote:
> >>> On Wed, May 24, 2023 at 12:24 AM Luis Chamberlain <mcgrof@...nel.org> wrote:
> >>>
> >>> This change broke compilation of BPF selftests in modules-next
> >>> branch:
> >>>
> >>> progs/bpf_iter_ksym.c:62:13: error: no member named 'pos_arch_end' in
> >>> 'struct kallsym_iter'
> >>>         if (!iter->pos_arch_end || iter->pos_arch_end > iter->pos)
> >>>              ~~~~  ^
> >>> progs/bpf_iter_ksym.c:62:35: error: no member named 'pos_arch_end' in
> >>> 'struct kallsym_iter'
> >>>         if (!iter->pos_arch_end || iter->pos_arch_end > iter->pos)
> >>>                                    ~~~~  ^
> >>>
> >>> I haven't looked into the proper fix for it yet.
> >>
> >> A quick attempt:
> >>
> >> Arnd, can you verify?
> >>
> >> diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_ksym.c 
> >> b/tools/testing/selftests/bpf/progs/bpf_iter_ksym.c
> >> index 5ddcc46fd886..521267818f4d 100644
> >> --- a/tools/testing/selftests/bpf/progs/bpf_iter_ksym.c
> >> +++ b/tools/testing/selftests/bpf/progs/bpf_iter_ksym.c
> >> @@ -59,9 +59,7 @@ int dump_ksym(struct bpf_iter__ksym *ctx)
> >>  	} else {
> >>  		BPF_SEQ_PRINTF(seq, "0x%llx %c %s ", value, type, iter->name);
> >>  	}
> >> -	if (!iter->pos_arch_end || iter->pos_arch_end > iter->pos)
> >> -		BPF_SEQ_PRINTF(seq, "CORE ");
> >> -	else if (!iter->pos_mod_end || iter->pos_mod_end > iter->pos)
> >> +	if (!iter->pos_mod_end || iter->pos_mod_end > iter->pos)
> >>  		BPF_SEQ_PRINTF(seq, "MOD ");
> >>  	else if (!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > 
> >> iter->pos)
> >>  		BPF_SEQ_PRINTF(seq, "FTRACE_MOD ");
> > 
> > This looks correct to me, but I'm still failing to cross-build
> > the selftests on my randconfig build setup, so I can't confirm that
> > this avoids the build failure, and I don't understand the code well
> > enough to be sure.
> >
> 
> Thanks for the fix! The change above works ; maybe having
> anything less than iter->pos_mod_end marked as a "CORE/MOD " symbol
> might be worth tweaking, but that's a minor thing.
> 
> before:
> 
>   CLNG-BPF [test_maps] bpf_iter_ksym.bpf.o
> progs/bpf_iter_ksym.c:62:13: error: no member named 'pos_arch_end' in
> 'struct kallsym_iter'
>         if (!iter->pos_arch_end || iter->pos_arch_end > iter->pos)
>              ~~~~  ^
> progs/bpf_iter_ksym.c:62:35: error: no member named 'pos_arch_end' in
> 'struct kallsym_iter'
>         if (!iter->pos_arch_end || iter->pos_arch_end > iter->pos)
>                                    ~~~~  ^
> 2 errors generated.
> 
> after the above is applied, bpf selftests build and iter ksym test
> passes:
> 
> $ sudo ./test_progs -t bpf_iter
> ...
> #12/37   bpf_iter/ksym:OK
> ...
> Summary: 3/39 PASSED, 0 SKIPPED, 0 FAILED
> 
> Feel free to add a
> 
> Tested-by: Alan Maguire <alan.maguire@...cle.com>

I just folded this into Arnd's patch and pushed to modules-next.

Thanks!

  Luis