Re: [PATCH] ftrace: x86: Fix a compile error about get_kernel_nofault()

Masami Hiramatsu
2025-02-06T11:54:55Z

On Thu, 6 Feb 2025 09:12:25 +0100
Peter Zijlstra <peterz@infradead.org> wrote:

>
> > +#ifdef CONFIG_HAVE_FENTRY
> > +/* Convert fentry address to the symbol address. */
> > +unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip)
> > +{
> > +#ifdef CONFIG_X86_KERNEL_IBT
> > + u32 instr;
> > +
> > + /* We want to be extra safe in case entry ip is on the page edge,
> > + * but otherwise we need to avoid get_kernel_nofault()'s overhead.
> > + */
> > + if ((fentry_ip & ~PAGE_MASK) < ENDBR_INSN_SIZE) {
> > + if (get_kernel_nofault(instr, (u32 *)(fentry_ip - ENDBR_INSN_SIZE)))
> > + return fentry_ip;
> > + } else {
> > + instr = *(u32 *)(fentry_ip - ENDBR_INSN_SIZE);
> > + }
> > + if (is_endbr(instr))
> > + fentry_ip -= ENDBR_INSN_SIZE;
> > +#endif
> > + return fentry_ip;
> > +}
> > +#endif
>
> Urgh, that reminds, me. I have a pile of patches cleaning up this mess.
> Let me go find them.

Thanks for cleaning up! So would it change the location of ENDBR and
symbol address?

Thanks,

--
Masami Hiramatsu (Google) <mhiramat@kernel.org>