Re: [PATCH bpf-next 1/2] arm64/ftrace,bpf: Fix partial regs after bpf_prog_run

[Jiri Olsa <olsajiri@gmail.com>]

On Wed, Jan 07, 2026 at 12:14:32PM -0500, Steven Rostedt wrote:
> On Wed, 7 Jan 2026 16:52:52 +0000
> Will Deacon <will@kernel.org> wrote:
> 
> > diff --git a/include/linux/ftrace_regs.h b/include/linux/ftrace_regs.h
> > index 15627ceea9bc..3ebd8cdac7c6 100644
> > --- a/include/linux/ftrace_regs.h
> > +++ b/include/linux/ftrace_regs.h
> > @@ -33,6 +33,15 @@ struct ftrace_regs;
> >  #define ftrace_regs_get_frame_pointer(fregs) \
> >         frame_pointer(&arch_ftrace_regs(fregs)->regs)
> >  
> > +#else
> > +
> > +static __always_inline void
> > +ftrace_partial_regs_update(const struct ftrace_regs *fregs, struct pt_regs *regs)
> > +{
> > +       ftrace_regs_set_instruction_pointer(fregs, instruction_pointer(regs));
> > +       ftrace_regs_set_return_value(fregs, regs_return_value(regs));
> > +}
> > +
> >  #endif /* HAVE_ARCH_FTRACE_REGS */
> >  
> >  /* This can be overridden by the architectures */
> 
> Hmm, maybe that would work. Of course you forgot to add the helper for the
> !HAVE_ARCH_FTRACE_REGS case ;-)

seems to work, will send new version with that

thanks,
jirka


---
diff --git a/include/linux/ftrace_regs.h b/include/linux/ftrace_regs.h
index 15627ceea9bc..4b053eb4c9d5 100644
--- a/include/linux/ftrace_regs.h
+++ b/include/linux/ftrace_regs.h
@@ -33,6 +33,18 @@ struct ftrace_regs;
 #define ftrace_regs_get_frame_pointer(fregs) \
 	frame_pointer(&arch_ftrace_regs(fregs)->regs)
 
+static __always_inline void
+ftrace_partial_regs_update(const struct ftrace_regs *fregs, struct pt_regs *regs) { }
+
+#else
+
+static __always_inline void
+ftrace_partial_regs_update(const struct ftrace_regs *fregs, struct pt_regs *regs)
+{
+	ftrace_regs_set_instruction_pointer(fregs, instruction_pointer(regs));
+	ftrace_regs_set_return_value(fregs, regs_return_value(regs));
+}
+
 #endif /* HAVE_ARCH_FTRACE_REGS */
 
 /* This can be overridden by the architectures */
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 6e076485bf70..3a17f79b20c2 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2564,6 +2564,7 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
 	old_run_ctx = bpf_set_run_ctx(&run_ctx.session_ctx.run_ctx);
 	err = bpf_prog_run(link->link.prog, regs);
 	bpf_reset_run_ctx(old_run_ctx);
+	ftrace_partial_regs_update(fregs, bpf_kprobe_multi_pt_regs_ptr());
 	rcu_read_unlock();
 
  out: