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Date:   Mon, 10 Jul 2023 17:37:24 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc:     Petr Pavlu <petr.pavlu@suse.com>, tglx@linutronix.de,
        mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
        hpa@zytor.com, samitolvanen@google.com, x86@kernel.org,
        linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 1/2] kprobes: Prohibit probing on CFI preamble symbol
Message-ID: <20230710153724.GA3040258@hirez.programming.kicks-ass.net>
References: <168899125356.80889.17967397360941194229.stgit@devnote2>
 <168899126450.80889.16200438320430187434.stgit@devnote2>
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On Mon, Jul 10, 2023 at 09:14:24PM +0900, Masami Hiramatsu (Google) wrote:


> +#ifdef CONFIG_CFI_CLANG
> +static bool is_cfi_preamble_symbol(unsigned long addr)
> +{
> +	char symbuf[KSYM_NAME_LEN];
> +
> +	if (lookup_symbol_name(addr, symbuf))
> +		return false;
> +
> +	return str_has_prefix("__cfi_", symbuf)
		|| str_has_prefix("__pfx_", symbol);

The __pfx_ symbols can happen when !CFI_CLANG but still having
FUNCTION_PADDING_BYTES.

> +}
> +#else
> +#define is_cfi_preamble_symbol(addr)	(0)
> +#endif

As such I think we can do the above unconditionally, without either
there should not be any matching symbols.