Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161313Ab3DECQM (ORCPT ); Thu, 4 Apr 2013 22:16:12 -0400 Received: from mail4.hitachi.co.jp ([133.145.228.5]:54381 "EHLO mail4.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161300Ab3DECQL (ORCPT ); Thu, 4 Apr 2013 22:16:11 -0400 Message-ID: <515E33E8.6050507@hitachi.com> Date: Fri, 05 Apr 2013 11:16:08 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 5.2; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Joonsoo Kim Cc: Oskar Andero , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, davem@davemloft.net, anil.s.keshavamurthy@intel.com, ananth@in.ibm.com, radovan.lekanovic@sonymobile.com, bjorn.davidsson@sonymobile.com, Toby Collett , "yrl.pp-manager.tt@hitachi.com" Subject: Re: Re: [PATCH v2 1/4] kprobes: delay blacklist symbol lookup until we actually need it References: <1365079889-21525-1-git-send-email-oskar.andero@sonymobile.com> <1365079889-21525-2-git-send-email-oskar.andero@sonymobile.com> <20130405005628.GA13624@lge.com> In-Reply-To: <20130405005628.GA13624@lge.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3635 Lines: 111 (2013/04/05 9:56), Joonsoo Kim wrote: > Hello, Oskar. > > On Thu, Apr 04, 2013 at 02:51:26PM +0200, Oskar Andero wrote: >> From: Toby Collett >> >> The symbol lookup can take a long time and kprobes is >> initialised very early in boot, so delay symbol lookup >> until the blacklist is first used. >> >> Cc: Masami Hiramatsu >> Cc: David S. Miller >> Reviewed-by: Radovan Lekanovic >> Signed-off-by: Toby Collett >> Signed-off-by: Oskar Andero >> --- >> kernel/kprobes.c | 98 ++++++++++++++++++++++++++++++++++---------------------- >> 1 file changed, 60 insertions(+), 38 deletions(-) >> >> diff --git a/kernel/kprobes.c b/kernel/kprobes.c >> index e35be53..0a270e5 100644 >> --- a/kernel/kprobes.c >> +++ b/kernel/kprobes.c >> @@ -68,6 +68,7 @@ >> #endif >> >> static int kprobes_initialized; >> +static int kprobe_blacklist_initialized; >> static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE]; >> static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE]; >> >> @@ -102,6 +103,60 @@ static struct kprobe_blackpoint kprobe_blacklist[] = { >> {NULL} /* Terminator */ >> }; >> >> +/* it can take some time ( > 100ms ) to initialise the >> + * blacklist so we delay this until we actually need it >> + */ >> +static void init_kprobe_blacklist(void) >> +{ >> + int i; >> + unsigned long offset = 0, size = 0; >> + char *modname, namebuf[128]; >> + const char *symbol_name; >> + void *addr; >> + struct kprobe_blackpoint *kb; >> + >> + mutex_lock(&kprobe_mutex); >> + if (kprobe_blacklist_initialized) >> + goto out; >> + >> + /* >> + * Lookup and populate the kprobe_blacklist. >> + * >> + * Unlike the kretprobe blacklist, we'll need to determine >> + * the range of addresses that belong to the said functions, >> + * since a kprobe need not necessarily be at the beginning >> + * of a function. >> + */ >> + for (kb = kprobe_blacklist; kb->name != NULL; kb++) { >> + kprobe_lookup_name(kb->name, addr); >> + if (!addr) >> + continue; >> + >> + kb->start_addr = (unsigned long)addr; >> + symbol_name = kallsyms_lookup(kb->start_addr, >> + &size, &offset, &modname, namebuf); >> + if (!symbol_name) >> + kb->range = 0; >> + else >> + kb->range = size; >> + } >> + >> + if (kretprobe_blacklist_size) { >> + /* lookup the function address from its name */ >> + for (i = 0; kretprobe_blacklist[i].name != NULL; i++) { >> + kprobe_lookup_name(kretprobe_blacklist[i].name, >> + kretprobe_blacklist[i].addr); >> + if (!kretprobe_blacklist[i].addr) >> + printk("kretprobe: lookup failed: %s\n", >> + kretprobe_blacklist[i].name); >> + } >> + } >> + kprobe_blacklist_initialized = 1; > > You need smp_wmb() before assigning 'kprobe_blacklist_initialized = 1'. > This guarantee that who see kprobe_blacklist_initialized = 1 will get > updated data of kprobe_blacklist. Right, to ensure blacklist is updated, memory barrier is required. > Please refer my previous patch once more :) > > And How about define kprobe_blacklist_initialized as boolean? Good idea :) Thank you, -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/