On Wed, 7 Jan 2026 14:16:05 +0000 Will Deacon <[email protected]> wrote:
> I still don't understand why we need anything new in the arch code for this. > > We've selected HAVE_ARCH_FTRACE_REGS and we implement > ftrace_regs_set_instruction_pointer() and ftrace_regs_set_return_value() > so the core code already has everything it needs to make this work > without additional arch support. I believe the issue is that the BPF code takes a pt_regs and does the update directly with that, and not the ftrace_regs. I'm guessing this is due to BPF programs modifying the pt_regs directly, and BPF programs do not yet understand ftrace_regs? Because arm64 requires making a copy of pt_regs as the ftrace_regs has a different layout, and the ftrace_regs is what does the changes, if the pt_regs passed to the BPF program modifies the values it needs a way to propagate that back to the ftrace_regs. -- Steve
