linux-kernel - Re: [PATCH 2/2] arm64: Make all entry code as non-kprobe-able

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Message-ID: <559A6075.5070502@hitachi.com>
Date:	Mon, 06 Jul 2015 20:03:17 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Pratyush Anand <panand@...hat.com>,
	linux-arm-kernel@...ts.infradead.org, linux@....linux.org.uk,
	catalin.marinas@....com, will.deacon@....com
CC:	linux-kernel@...r.kernel.org, wcohen@...hat.com,
	dave.long@...aro.org, steve.capper@...aro.org
Subject: Re: [PATCH 2/2] arm64: Make all entry code as non-kprobe-able

On 2015/07/06 14:03, Pratyush Anand wrote:
> Entry symbols are not kprobe safe. So blacklist them for kprobing.

As I've said, you can also use _ASM_NOKPROBE().
This patch itself looks good to me, but I'd like to ask arm64
maintainers' opinion, whether they accept introducing entry-text
section only for this purpose or not.

Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>

Thank you,

> 
> Signed-off-by: Pratyush Anand <panand@...hat.com>
> ---
>  arch/arm64/kernel/entry.S       | 3 +++
>  arch/arm64/kernel/kprobes.c     | 9 +++++++++
>  arch/arm64/kernel/vmlinux.lds.S | 1 +
>  3 files changed, 13 insertions(+)
> 
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index a7691a378668..2ea24f6bc06b 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -202,6 +202,7 @@ tsk	.req	x28		// current thread_info
>   * Exception vectors.
>   */
>  
> +	.section ".entry.text", "ax"
>  	.align	11
>  ENTRY(vectors)
>  	ventry	el1_sync_invalid		// Synchronous EL1t
> @@ -737,3 +738,5 @@ ENTRY(sys_rt_sigreturn_wrapper)
>  	mov	x0, sp
>  	b	sys_rt_sigreturn
>  ENDPROC(sys_rt_sigreturn_wrapper)
> +
> +	.section ".text", "ax"
> diff --git a/arch/arm64/kernel/kprobes.c b/arch/arm64/kernel/kprobes.c
> index 6c9f8b5f04ce..9bc02c151f7f 100644
> --- a/arch/arm64/kernel/kprobes.c
> +++ b/arch/arm64/kernel/kprobes.c
> @@ -28,6 +28,7 @@
>  #include <asm/debug-monitors.h>
>  #include <asm/system_misc.h>
>  #include <asm/insn.h>
> +#include <asm-generic/sections.h>
>  
>  #include "kprobes.h"
>  #include "kprobes-arm64.h"
> @@ -661,6 +662,14 @@ int __kprobes arch_trampoline_kprobe(struct kprobe *p)
>  	return 0;
>  }
>  
> +bool arch_within_kprobe_blacklist(unsigned long addr)
> +{
> +	return  (addr >= (unsigned long)__kprobes_text_start &&
> +		 addr < (unsigned long)__kprobes_text_end) ||
> +		(addr >= (unsigned long)__entry_text_start &&
> +		 addr < (unsigned long)__entry_text_end);
> +}
> +
>  int __init arch_init_kprobes(void)
>  {
>  	return 0;
> diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
> index 1fa6adc7aa83..11fb2b0117d0 100644
> --- a/arch/arm64/kernel/vmlinux.lds.S
> +++ b/arch/arm64/kernel/vmlinux.lds.S
> @@ -97,6 +97,7 @@ SECTIONS
>  			*(.exception.text)
>  			__exception_text_end = .;
>  			IRQENTRY_TEXT
> +			ENTRY_TEXT
>  			TEXT_TEXT
>  			SCHED_TEXT
>  			LOCK_TEXT
> 


-- 
Masami HIRAMATSU
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu.pt@...achi.com
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