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Date: Thu, 6 Feb 2025 09:12:25 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	Gabriel de Perthuis <g2p.code@gmail.com>,
	Haiyue Wang <haiyuewa@163.com>,
	Sami Tolvanen <samitolvanen@google.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H . Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
	linux-trace-kernel@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] ftrace: x86: Fix a compile error about
 get_kernel_nofault()
Message-ID: <20250206081225.GI7145@noisy.programming.kicks-ass.net>
References: <173881156244.211648.1242168038709680511.stgit@devnote2>
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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.