Re: [PATCH] uprobes/x86: Rename arch_uprobe->def into ->dflt, minor comment updates

[Jim Keniston]

On Sun, 2014-06-01 at 21:25 +0200, Oleg Nesterov wrote:
> Purely cosmetic, no changes in .o,
> 
> 1. As Jim pointed out arch_uprobe->def looks ambiguous, rename it to
>    ->dflt.
> 
> 2. Add the comment into default_post_xol_op() to explain "regs->sp +=".
> 
> 3. Remove the stale part of the comment in arch_uprobe_analyze_insn().
> 
> Suggested-by: Jim Keniston <jkenisto@xxxxxxxxxx>
> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>

Looks good.  Thanks.

Reviewed-by: Jim Keniston <jkenisto@xxxxxxxxxx>

> ---
>  arch/x86/include/asm/uprobes.h |    2 +-
>  arch/x86/kernel/uprobes.c      |   37 ++++++++++++++++++-------------------
>  2 files changed, 19 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
> index 7be3c07..b3d9442 100644
> --- a/arch/x86/include/asm/uprobes.h
> +++ b/arch/x86/include/asm/uprobes.h
> @@ -52,7 +52,7 @@ struct arch_uprobe {
>  		struct {
>  			u8	fixups;
>  			u8	ilen;
> -		} 			def;
> +		} 			dflt;
>  	};
>  };
> 
> diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
> index fcf6279..33e239f 100644
> --- a/arch/x86/kernel/uprobes.c
> +++ b/arch/x86/kernel/uprobes.c
> @@ -254,7 +254,7 @@ static inline bool is_64bit_mm(struct mm_struct *mm)
>   * If arch_uprobe->insn doesn't use rip-relative addressing, return
>   * immediately.  Otherwise, rewrite the instruction so that it accesses
>   * its memory operand indirectly through a scratch register.  Set
> - * def->fixups accordingly. (The contents of the scratch register
> + * dflt->fixups accordingly. (The contents of the scratch register
>   * will be saved before we single-step the modified instruction,
>   * and restored afterward).
>   *
> @@ -372,14 +372,14 @@ static void riprel_analyze(struct arch_uprobe *auprobe, struct insn *insn)
>  	 */
>  	if (reg != 6 && reg2 != 6) {
>  		reg2 = 6;
> -		auprobe->def.fixups |= UPROBE_FIX_RIP_SI;
> +		auprobe->dflt.fixups |= UPROBE_FIX_RIP_SI;
>  	} else if (reg != 7 && reg2 != 7) {
>  		reg2 = 7;
> -		auprobe->def.fixups |= UPROBE_FIX_RIP_DI;
> +		auprobe->dflt.fixups |= UPROBE_FIX_RIP_DI;
>  		/* TODO (paranoia): force maskmovq to not use di */
>  	} else {
>  		reg2 = 3;
> -		auprobe->def.fixups |= UPROBE_FIX_RIP_BX;
> +		auprobe->dflt.fixups |= UPROBE_FIX_RIP_BX;
>  	}
>  	/*
>  	 * Point cursor at the modrm byte.  The next 4 bytes are the
> @@ -398,9 +398,9 @@ static void riprel_analyze(struct arch_uprobe *auprobe, struct insn *insn)
>  static inline unsigned long *
>  scratch_reg(struct arch_uprobe *auprobe, struct pt_regs *regs)
>  {
> -	if (auprobe->def.fixups & UPROBE_FIX_RIP_SI)
> +	if (auprobe->dflt.fixups & UPROBE_FIX_RIP_SI)
>  		return &regs->si;
> -	if (auprobe->def.fixups & UPROBE_FIX_RIP_DI)
> +	if (auprobe->dflt.fixups & UPROBE_FIX_RIP_DI)
>  		return &regs->di;
>  	return &regs->bx;
>  }
> @@ -411,18 +411,18 @@ scratch_reg(struct arch_uprobe *auprobe, struct pt_regs *regs)
>   */
>  static void riprel_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
>  {
> -	if (auprobe->def.fixups & UPROBE_FIX_RIP_MASK) {
> +	if (auprobe->dflt.fixups & UPROBE_FIX_RIP_MASK) {
>  		struct uprobe_task *utask = current->utask;
>  		unsigned long *sr = scratch_reg(auprobe, regs);
> 
>  		utask->autask.saved_scratch_register = *sr;
> -		*sr = utask->vaddr + auprobe->def.ilen;
> +		*sr = utask->vaddr + auprobe->dflt.ilen;
>  	}
>  }
> 
>  static void riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
>  {
> -	if (auprobe->def.fixups & UPROBE_FIX_RIP_MASK) {
> +	if (auprobe->dflt.fixups & UPROBE_FIX_RIP_MASK) {
>  		struct uprobe_task *utask = current->utask;
>  		unsigned long *sr = scratch_reg(auprobe, regs);
> 
> @@ -499,16 +499,16 @@ static int default_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs
>  	struct uprobe_task *utask = current->utask;
> 
>  	riprel_post_xol(auprobe, regs);
> -	if (auprobe->def.fixups & UPROBE_FIX_IP) {
> +	if (auprobe->dflt.fixups & UPROBE_FIX_IP) {
>  		long correction = utask->vaddr - utask->xol_vaddr;
>  		regs->ip += correction;
> -	} else if (auprobe->def.fixups & UPROBE_FIX_CALL) {
> -		regs->sp += sizeof_long();
> -		if (push_ret_address(regs, utask->vaddr + auprobe->def.ilen))
> +	} else if (auprobe->dflt.fixups & UPROBE_FIX_CALL) {
> +		regs->sp += sizeof_long(); /* Pop incorrect return address */
> +		if (push_ret_address(regs, utask->vaddr + auprobe->dflt.ilen))
>  			return -ERESTART;
>  	}
>  	/* popf; tell the caller to not touch TF */
> -	if (auprobe->def.fixups & UPROBE_FIX_SETF)
> +	if (auprobe->dflt.fixups & UPROBE_FIX_SETF)
>  		utask->autask.saved_tf = true;
> 
>  	return 0;
> @@ -711,12 +711,11 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
> 
>  	/*
>  	 * Figure out which fixups default_post_xol_op() will need to perform,
> -	 * and annotate def->fixups accordingly. To start with, ->fixups is
> -	 * either zero or it reflects rip-related fixups.
> +	 * and annotate dflt->fixups accordingly.
>  	 */
>  	switch (OPCODE1(&insn)) {
>  	case 0x9d:		/* popf */
> -		auprobe->def.fixups |= UPROBE_FIX_SETF;
> +		auprobe->dflt.fixups |= UPROBE_FIX_SETF;
>  		break;
>  	case 0xc3:		/* ret or lret -- ip is correct */
>  	case 0xcb:
> @@ -742,8 +741,8 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
>  		riprel_analyze(auprobe, &insn);
>  	}
> 
> -	auprobe->def.ilen = insn.length;
> -	auprobe->def.fixups |= fix_ip_or_call;
> +	auprobe->dflt.ilen = insn.length;
> +	auprobe->dflt.fixups |= fix_ip_or_call;
> 
>  	auprobe->ops = &default_xol_ops;
>  	return 0;


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