On Wed, Aug 17, 2022 at 2:29 AM Jiri Olsa <olsajiri@xxxxxxxxx> wrote: > > On Tue, Aug 16, 2022 at 08:56:33AM +0200, Jiri Olsa wrote: > > On Mon, Aug 15, 2022 at 05:48:44PM +0200, Peter Zijlstra wrote: > > > On Mon, Aug 15, 2022 at 08:35:53AM -0700, Alexei Starovoitov wrote: > > > > On Mon, Aug 15, 2022 at 8:28 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > > > > > > > > On Mon, Aug 15, 2022 at 08:17:42AM -0700, Alexei Starovoitov wrote: > > > > > > It's hiding a fake function from ftrace, since it's not a function > > > > > > and ftrace infra shouldn't show it tracing logs. > > > > > > In other words it's a _notrace_ function with nop5. > > > > > > > > > > Then make it a notrace function with a nop5 in it. That isn't hard. > > > > > > > > That's exactly what we're trying to do. > > > > > > All the while claiming ftrace is broken while it is not. > > > > > > > Jiri's patch is one way to achieve that. > > > > > > Fairly horrible way. > > > > > > > What is your suggestion? > > > > > > Mailed it already. > > > > > > > Move it from C to asm ? > > > > > > Would be much better than proposed IMO. > > > > nice, that would be independent of the compiler atributes > > and config checking.. will check on this one ;-) > > how about something like below? > > dispatcher code is generated only for x86_64, so that will be covered > by the assembly version (free of ftrace table) other archs stay same > > jirka > > > ---- > diff --git a/arch/x86/net/Makefile b/arch/x86/net/Makefile > index 383c87300b0d..94964002eaae 100644 > --- a/arch/x86/net/Makefile > +++ b/arch/x86/net/Makefile > @@ -7,4 +7,5 @@ ifeq ($(CONFIG_X86_32),y) > obj-$(CONFIG_BPF_JIT) += bpf_jit_comp32.o > else > obj-$(CONFIG_BPF_JIT) += bpf_jit_comp.o > + obj-$(CONFIG_BPF_JIT) += bpf_dispatcher.o > endif > diff --git a/arch/x86/net/bpf_dispatcher.S b/arch/x86/net/bpf_dispatcher.S > new file mode 100644 > index 000000000000..65790a1286e8 > --- /dev/null > +++ b/arch/x86/net/bpf_dispatcher.S > @@ -0,0 +1,10 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#include <linux/linkage.h> > +#include <asm/nops.h> > +#include <asm/nospec-branch.h> > + > + .text > +SYM_FUNC_START(bpf_dispatcher_xdp_func) > + ASM_NOP5 > + JMP_NOSPEC rdx > +SYM_FUNC_END(bpf_dispatcher_xdp_func) Wait. Why asm ? Did you try Peter's suggestion: __attribute__((__no_instrument_function__)) __attribute__((patchable_function_entry(5))) ?
