linux-kernel - Re: [PATCH 3/5] kprobes: constify check_kprobe_address

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Date:	Mon, 21 Jan 2013 20:49:04 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	rostedt@...dmis.org, fweisbec@...il.com, rusty@...tcorp.com.au,
	ananth@...ibm.com, anil.s.keshavamurthy@...el.com,
	jbaron@...hat.com, x86@...nel.org, linux-kernel@...r.kernel.org,
	"yrl.pp-manager.tt@...achi.com" <yrl.pp-manager.tt@...achi.com>
Subject: Re: [PATCH 3/5] kprobes: constify check_kprobe_address_safe and
 friends

(2013/01/10 8:09), Sasha Levin wrote:
> Constify the parameters of lookup functions.
> 
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
> ---
>  arch/x86/kernel/kprobes-opt.c | 8 ++++----
>  kernel/kprobes.c              | 2 +-
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kernel/kprobes-opt.c b/arch/x86/kernel/kprobes-opt.c
> index c5e410e..5876966 100644
> --- a/arch/x86/kernel/kprobes-opt.c
> +++ b/arch/x86/kernel/kprobes-opt.c
> @@ -192,7 +192,7 @@ static int __kprobes copy_optimized_instructions(u8 *dest, u8 *src)
>  }
>  
>  /* Check whether insn is indirect jump */
> -static int __kprobes insn_is_indirect_jump(struct insn *insn)
> +static int __kprobes insn_is_indirect_jump(const struct insn *insn)
>  {
>  	return ((insn->opcode.bytes[0] == 0xff &&
>  		(X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */
> @@ -200,7 +200,7 @@ static int __kprobes insn_is_indirect_jump(struct insn *insn)
>  }
>  
>  /* Check whether insn jumps into specified address range */
> -static int insn_jump_into_range(struct insn *insn, unsigned long start, int len)
> +static int insn_jump_into_range(const struct insn *insn, unsigned long start, int len)
>  {
>  	unsigned long target = 0;
>  

These are OK for me.

> @@ -278,7 +278,7 @@ static int __kprobes can_optimize(unsigned long paddr)
>  }
>  
>  /* Check optimized_kprobe can actually be optimized. */
> -int __kprobes arch_check_optimized_kprobe(struct optimized_kprobe *op)
> +int __kprobes arch_check_optimized_kprobe(const struct optimized_kprobe *op)
>  {
>  	int i;
>  	struct kprobe *p;

This can be change optimized_kprobe inside, e.g. change flags.
IMHO, I don't like to change this interface.

> @@ -294,7 +294,7 @@ int __kprobes arch_check_optimized_kprobe(struct optimized_kprobe *op)
>  
>  /* Check the addr is within the optimized instructions. */
>  int __kprobes
> -arch_within_optimized_kprobe(struct optimized_kprobe *op, unsigned long addr)
> +arch_within_optimized_kprobe(const struct optimized_kprobe *op, unsigned long addr)
>  {
>  	return ((unsigned long)op->kp.addr <= addr &&
>  		(unsigned long)op->kp.addr + op->optinsn.size > addr);

This is OK for me. But you need to update the prototype in
include/linux/kprobes.h too.

> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 098f396..7daddb0 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1402,7 +1402,7 @@ static inline int check_kprobe_rereg(struct kprobe *p)
>  	return ret;
>  }
>  
> -static __kprobes int check_kprobe_address_safe(struct kprobe *p,
> +static __kprobes int check_kprobe_address_safe(const struct kprobe *p,
>  					       struct module **probed_mod)
>  {
>  	int ret = 0;
> 

No, p is NOT constant in this function. This changes p->flags.

---
#ifdef KPROBES_CAN_USE_FTRACE
                /* Given address is not on the instruction boundary */
                if ((unsigned long)p->addr != ftrace_addr)
                        return -EILSEQ;
                p->flags |= KPROBE_FLAG_FTRACE;
#else   /* !KPROBES_CAN_USE_FTRACE */
---

Thank you,

-- 
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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