Re: [PATCH] LoongArch: uprobes: make UPROBE_SWBP_INSN/UPROBE_XOLBP_INSN constant

Oleg Nesterov
2024-06-27T17:39:53Z

On 06/27, Andrii Nakryiko wrote:
>
> Acked-by: Andrii Nakryiko <andrii@kernel.org>

Thanks!

> > --- a/arch/loongarch/kernel/uprobes.c
> > +++ b/arch/loongarch/kernel/uprobes.c
> > @@ -7,6 +7,14 @@
> >
> > #define UPROBE_TRAP_NR UINT_MAX
> >
> > +static __init int check_emit_break(void)
> > +{
> > + BUG_ON(UPROBE_SWBP_INSN != larch_insn_gen_break(BRK_UPROBE_BP));
> > + BUG_ON(UPROBE_XOLBP_INSN != larch_insn_gen_break(BRK_UPROBE_XOLBP));
> > + return 0;
> > +}
> > +arch_initcall(check_emit_break);
> > +
>
> I wouldn't even bother with this, but whatever.

Agreed, this looks a bit ugly. I did this only because I can not test
this (hopefully trivial) patch and the maintainers didn't reply.

If LoongArch boots at least once with this change, this run-time check
can be removed.

And just in case... I didn't dare to make a more "generic" change, but
perhaps KPROBE_BP_INSN and KPROBE_SSTEPBP_INSN should be redefined the
same way for micro-optimization. In this case __emit_break() should be
probably moved into arch/loongarch/include/asm/inst.h.

Oleg.