Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161504Ab3DEKAz (ORCPT ); Fri, 5 Apr 2013 06:00:55 -0400 Received: from seldrel01.sonyericsson.com ([212.209.106.2]:6172 "EHLO seldrel01.sonyericsson.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752035Ab3DEKAw (ORCPT ); Fri, 5 Apr 2013 06:00:52 -0400 From: Oskar Andero Date: Fri, 5 Apr 2013 12:00:49 +0200 To: Masami Hiramatsu CC: Joonsoo Kim , "linux-kernel@vger.kernel.org" , "linux-arch@vger.kernel.org" , "davem@davemloft.net" , "anil.s.keshavamurthy@intel.com" , "ananth@in.ibm.com" , "Lekanovic, Radovan" , =?iso-8859-1?Q?Davidsson=2C_Bj=F6rn?= , 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 Message-ID: <20130405100049.GI2481@caracas.corpusers.net> 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> <515E33E8.6050507@hitachi.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <515E33E8.6050507@hitachi.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3775 Lines: 112 Thanks for your input guys! On 04:16 Fri 05 Apr , Masami Hiramatsu wrote: > (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. Agreed. > > Please refer my previous patch once more :) > > > > And How about define kprobe_blacklist_initialized as boolean? > > Good idea :) > I'll fix it for v3. -Oskar > -- 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/