linux-kernel - Re: [Patch v2 2/3] kprobes: allow to specify custum allocator for insn caches

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Date:	Mon, 26 Aug 2013 11:21:56 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [Patch v2 2/3] kprobes: allow to specify custum allocator for
 insn caches

(2013/08/23 20:04), Heiko Carstens wrote:
> The current two insn slot caches both use module_alloc/module_free
> to allocate and free insn slot cache pages.
> For s390 this is not sufficient since there is the need to allocate
> insn slots that are either within the vmalloc module area or within
> dma memory.
> Therefore add a mechanism which allows to specify an own allocator
> for an own insn slot cache.
> 

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

Thank you!

> Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
> ---
>  include/linux/kprobes.h |    2 ++
>  kernel/kprobes.c        |   20 ++++++++++++++++++--
>  2 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
> index 077f653..925eaf2 100644
> --- a/include/linux/kprobes.h
> +++ b/include/linux/kprobes.h
> @@ -268,6 +268,8 @@ extern void kprobes_inc_nmissed_count(struct kprobe *p);
>  
>  struct kprobe_insn_cache {
>  	struct mutex mutex;
> +	void *(*alloc)(void);	/* allocate insn page */
> +	void (*free)(void *);	/* free insn page */
>  	struct list_head pages; /* list of kprobe_insn_page */
>  	size_t insn_size;	/* size of instruction slot */
>  	int nr_garbage;
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 9e4912d..a0d367a 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -112,6 +112,7 @@ static struct kprobe_blackpoint kprobe_blacklist[] = {
>  struct kprobe_insn_page {
>  	struct list_head list;
>  	kprobe_opcode_t *insns;		/* Page of instruction slots */
> +	struct kprobe_insn_cache *cache;
>  	int nused;
>  	int ngarbage;
>  	char slot_used[];
> @@ -132,8 +133,20 @@ enum kprobe_slot_state {
>  	SLOT_USED = 2,
>  };
>  
> +static void *alloc_insn_page(void)
> +{
> +	return module_alloc(PAGE_SIZE);
> +}
> +
> +static void free_insn_page(void *page)
> +{
> +	module_free(NULL, page);
> +}
> +
>  struct kprobe_insn_cache kprobe_insn_slots = {
>  	.mutex = __MUTEX_INITIALIZER(kprobe_insn_slots.mutex),
> +	.alloc = alloc_insn_page,
> +	.free = free_insn_page,
>  	.pages = LIST_HEAD_INIT(kprobe_insn_slots.pages),
>  	.insn_size = MAX_INSN_SIZE,
>  	.nr_garbage = 0,
> @@ -182,7 +195,7 @@ kprobe_opcode_t __kprobes *__get_insn_slot(struct kprobe_insn_cache *c)
>  	 * kernel image and loaded module images reside. This is required
>  	 * so x86_64 can correctly handle the %rip-relative fixups.
>  	 */
> -	kip->insns = module_alloc(PAGE_SIZE);
> +	kip->insns = c->alloc();
>  	if (!kip->insns) {
>  		kfree(kip);
>  		goto out;
> @@ -192,6 +205,7 @@ kprobe_opcode_t __kprobes *__get_insn_slot(struct kprobe_insn_cache *c)
>  	kip->slot_used[0] = SLOT_USED;
>  	kip->nused = 1;
>  	kip->ngarbage = 0;
> +	kip->cache = c;
>  	list_add(&kip->list, &c->pages);
>  	slot = kip->insns;
>  out:
> @@ -213,7 +227,7 @@ static int __kprobes collect_one_slot(struct kprobe_insn_page *kip, int idx)
>  		 */
>  		if (!list_is_singular(&kip->list)) {
>  			list_del(&kip->list);
> -			module_free(NULL, kip->insns);
> +			kip->cache->free(kip->insns);
>  			kfree(kip);
>  		}
>  		return 1;
> @@ -274,6 +288,8 @@ out:
>  /* For optimized_kprobe buffer */
>  struct kprobe_insn_cache kprobe_optinsn_slots = {
>  	.mutex = __MUTEX_INITIALIZER(kprobe_optinsn_slots.mutex),
> +	.alloc = alloc_insn_page,
> +	.free = free_insn_page,
>  	.pages = LIST_HEAD_INIT(kprobe_optinsn_slots.pages),
>  	/* .insn_size is initialized later */
>  	.nr_garbage = 0,
> 


-- 
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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