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

Peter Zijlstra
2025-02-06T08:12:37Z

On Thu, Feb 06, 2025 at 12:12:42PM +0900, Masami Hiramatsu (Google) 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.