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

Jiri Olsa
2022-08-30T13:51:19Z

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@kernel.org/
> > ---
> > 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(-)
> >
>