linux-kernel - Re: [PATCH v2 10/11] uprobes: Add the "enum rp_check ctx" arg to arch_uretprobe_is

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Date:	Tue, 7 Jul 2015 15:08:59 +0200
From:	Anton Arapov <arapov@...il.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ananth Mavinakayanahalli <ananth@...ibm.com>,
	David Long <dave.long@...aro.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Jan Willeke <willeke@...ibm.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	Mark Wielaard <mjw@...hat.com>,
	Pratyush Anand <panand@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 10/11] uprobes: Add the "enum rp_check ctx" arg to
 arch_uretprobe_is_alive()

On Tue, Jul 07, 2015 at 03:23:10AM +0200, Oleg Nesterov wrote:
> arch/x86 doesn't care (so far), but as Pratyush Anand pointed out
> other architectures might want why arch_uretprobe_is_alive() was
> called and use different checks depending on the context. Add the
> new argument to distinguish 2 callers.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Acked-by: Anton Arapov <arapov@...il.com>

> ---
>  arch/x86/kernel/uprobes.c |    3 ++-
>  include/linux/uprobes.h   |    7 ++++++-
>  kernel/events/uprobes.c   |    9 ++++++---
>  3 files changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
> index 9d5f570..67eb168 100644
> --- a/arch/x86/kernel/uprobes.c
> +++ b/arch/x86/kernel/uprobes.c
> @@ -994,7 +994,8 @@ arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs
>  	return -1;
>  }
>  
> -bool arch_uretprobe_is_alive(struct return_instance *ret, struct pt_regs *regs)
> +bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
> +				struct pt_regs *regs)
>  {
>  	return regs->sp <= ret->stack;
>  }
> diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
> index 7ab6d2c..c0a5402 100644
> --- a/include/linux/uprobes.h
> +++ b/include/linux/uprobes.h
> @@ -102,6 +102,11 @@ struct return_instance {
>  	struct return_instance	*next;		/* keep as stack */
>  };
>  
> +enum rp_check {
> +	RP_CHECK_CALL,
> +	RP_CHECK_RET,
> +};
> +
>  struct xol_area;
>  
>  struct uprobes_state {
> @@ -138,7 +143,7 @@ extern bool arch_uprobe_xol_was_trapped(struct task_struct *tsk);
>  extern int  arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data);
>  extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs *regs);
>  extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs);
> -extern bool arch_uretprobe_is_alive(struct return_instance *ret, struct pt_regs *regs);
> +extern bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx, struct pt_regs *regs);
>  extern bool arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs);
>  extern void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
>  					 void *src, unsigned long len);
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 7e61c8c..df5661a 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1514,7 +1514,9 @@ static unsigned long get_trampoline_vaddr(void)
>  static void cleanup_return_instances(struct uprobe_task *utask, struct pt_regs *regs)
>  {
>  	struct return_instance *ri = utask->return_instances;
> -	while (ri && !arch_uretprobe_is_alive(ri, regs)) {
> +	enum rp_check ctx = RP_CHECK_CALL;
> +
> +	while (ri && !arch_uretprobe_is_alive(ri, ctx, regs)) {
>  		ri = free_ret_instance(ri);
>  		utask->depth--;
>  	}
> @@ -1805,7 +1807,7 @@ static void handle_trampoline(struct pt_regs *regs)
>  		 * could hit this trampoline on return. TODO: sigaltstack().
>  		 */
>  		next = find_next_ret_chain(ri);
> -		valid = !next || arch_uretprobe_is_alive(next, regs);
> +		valid = !next || arch_uretprobe_is_alive(next, RP_CHECK_RET, regs);
>  
>  		instruction_pointer_set(regs, ri->orig_ret_vaddr);
>  		do {
> @@ -1830,7 +1832,8 @@ bool __weak arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs)
>  	return false;
>  }
>  
> -bool __weak arch_uretprobe_is_alive(struct return_instance *ret, struct pt_regs *regs)
> +bool __weak arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
> +					struct pt_regs *regs)
>  {
>  	return true;
>  }
> -- 
> 1.5.5.1
> 
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