Re: [PATCH bpf-next 0/2] bpf,ftrace: bpf dispatcher function fix

[Jiri Olsa <olsajiri@xxxxxxxxx>]

On Tue, Aug 30, 2022 at 12:25:25AM +0200, Daniel Borkmann wrote:
> On 8/26/22 8:46 PM, Jiri Olsa wrote:
> > hi,
> > as discussed [1] sending fix that moves bpf dispatcher function of out
> > ftrace locations together with Peter's HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
> > dependency change.
> 
> Looks like the series breaks s390x builds; BPF CI link:
> 
> https://github.com/kernel-patches/bpf/runs/8079411784?check_suite_focus=true
> 
>   [...]
>     CC      net/xfrm/xfrm_state.o
>     CC      net/packet/af_packet.o
>   {standard input}: Assembler messages:
>   {standard input}:16055: Error: bad expression
>   {standard input}:16056: Error: bad expression
>   {standard input}:16057: Error: bad expression
>   {standard input}:16058: Error: bad expression
>   {standard input}:16059: Error: bad expression
>     CC      drivers/s390/char/raw3270.o
>     CC      net/ipv6/ip6_output.o
>   [...]
>     CC      net/xfrm/xfrm_output.o
>     CC      net/ipv6/ip6_input.o
>   {standard input}:16055: Error: invalid operands (*ABS* and *UND* sections) for `%'
>   {standard input}:16056: Error: invalid operands (*ABS* and *UND* sections) for `%'
>   {standard input}:16057: Error: invalid operands (*ABS* and *UND* sections) for `%'
>   {standard input}:16058: Error: invalid operands (*ABS* and *UND* sections) for `%'
>   {standard input}:16059: Error: invalid operands (*ABS* and *UND* sections) for `%'
>   make[3]: *** [scripts/Makefile.build:249: net/core/filter.o] Error 1
>   make[2]: *** [scripts/Makefile.build:465: net/core] Error 2
>   make[2]: *** Waiting for unfinished jobs....
>     CC      net/ipv4/tcp_fastopen.o
>   [...]
>     CC      lib/percpu-refcount.o
>   make[1]: *** [Makefile:1855: net] Error 2
>     CC      lib/rhashtable.o
>   make[1]: *** Waiting for unfinished jobs....
>     CC      lib/base64.o
>   [...]
>     AR      lib/built-in.a
>     CC      kernel/kheaders.o
>     AR      kernel/built-in.a
>   make: *** [Makefile:353: __build_one_by_one] Error 2
>   Error: Process completed with exit code 2.


it does not break on my cross build with gcc 12, but I can
reproduce with gcc 8 (CI seems to be on gcc 9)

the problem seems to be wrong assembler code with extra '%'
that's generated for patchable_function_entry(5)

gcc 8 generates:

.LPFE1:
        nopr    %%r0
        nopr    %%r0
        nopr    %%r0
        nopr    %%r0
        nopr    %%r0

and gcc 12 generates:

.LPFE1:
        nopr    %r0
        nopr    %r0
        nopr    %r0
        nopr    %r0
        nopr    %r0

perhaps we need to upgrade gcc in CI? cc-ing Ilya, any idea?

thanks,
jirka

> 
> > [1] https://lore.kernel.org/bpf/20220722110811.124515-1-jolsa@xxxxxxxxxx/
> > ---
> > Jiri Olsa (1):
> >        bpf: Move bpf_dispatcher function out of ftrace locations
> > 
> > Peter Zijlstra (Intel) (1):
> >        ftrace: Add HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
> > 
> >   arch/x86/Kconfig                  |  1 +
> >   include/asm-generic/vmlinux.lds.h | 11 ++++++++++-
> >   include/linux/bpf.h               |  2 ++
> >   kernel/trace/Kconfig              |  6 ++++++
> >   tools/objtool/check.c             |  3 ++-
> >   5 files changed, 21 insertions(+), 2 deletions(-)
> > 
>