linux-kernel - Re: [PATCH v2 2/4] arm64: kprobes: Remove unneeded RODATA check

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Message-ID: <20190115112016.GD43491@lakrids.cambridge.arm.com>
Date:   Tue, 15 Jan 2019 11:20:17 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Pratyush Anand <panand@...hat.com>,
        "David A . Long" <dave.long@...aro.org>,
        linux-arm-kernel@...ts.infradead.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        James Morse <james.morse@....com>
Subject: Re: [PATCH v2 2/4] arm64: kprobes: Remove unneeded RODATA check

On Tue, Jan 15, 2019 at 03:24:36PM +0900, Masami Hiramatsu wrote:
> Remove unneeded RODATA check from arch_prepare_kprobe().
> 
> Since check_kprobe_address_safe() already ensured that
> the probe address is in kernel text, we don't need to
> check whether the address in RODATA or not. That must
> be always false.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>

Reviewed-by: Mark Rutland <mark.rutland@....com>

Mark.

> ---
>  arch/arm64/kernel/probes/kprobes.c |    6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
> index b2d4b7428ebc..1dae500d0a81 100644
> --- a/arch/arm64/kernel/probes/kprobes.c
> +++ b/arch/arm64/kernel/probes/kprobes.c
> @@ -91,8 +91,6 @@ static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
>  int __kprobes arch_prepare_kprobe(struct kprobe *p)
>  {
>  	unsigned long probe_addr = (unsigned long)p->addr;
> -	extern char __start_rodata[];
> -	extern char __end_rodata[];
>  
>  	if (probe_addr & 0x3)
>  		return -EINVAL;
> @@ -106,10 +104,6 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
>  	if (search_exception_tables(probe_addr))
>  		return -EINVAL;
>  
> -	if (probe_addr >= (unsigned long) __start_rodata &&
> -	    probe_addr <= (unsigned long) __end_rodata)
> -		return -EINVAL;
> -
>  	/* decode instruction */
>  	switch (arm_kprobe_decode_insn(p->addr, &p->ainsn)) {
>  	case INSN_REJECTED:	/* insn not supported */
>