Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755370Ab0GJNsx (ORCPT ); Sat, 10 Jul 2010 09:48:53 -0400 Received: from pfepa.post.tele.dk ([195.41.46.235]:35278 "EHLO pfepa.post.tele.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753560Ab0GJNsv (ORCPT ); Sat, 10 Jul 2010 09:48:51 -0400 Date: Sat, 10 Jul 2010 15:48:49 +0200 From: Sam Ravnborg To: Steven Rostedt Cc: Zeev Tarantov , Linus Torvalds , LKML , Ingo Molnar , Frederic Weisbecker , Andrew Morton , "Rafael J. Wysocki" Subject: Re: [PATCH] tracing: properly align linker defined symbols Message-ID: <20100710134849.GA15800@merkur.ravnborg.org> References: <1278705402.1537.157.camel@gandalf.stny.rr.com> <20100709203301.GA13839@merkur.ravnborg.org> <1278721339.1537.166.camel@gandalf.stny.rr.com> <20100710063459.GA14596@merkur.ravnborg.org> <1278761646.1537.182.camel@gandalf.stny.rr.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1278761646.1537.182.camel@gandalf.stny.rr.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1998 Lines: 60 On Sat, Jul 10, 2010 at 07:34:05AM -0400, Steven Rostedt wrote: > On Sat, 2010-07-10 at 13:18 +0300, Zeev Tarantov wrote: > > On Sat, Jul 10, 2010 at 09:35, Sam Ravnborg wrote: > > > > +/* > > > + * Align to a 32 byte boundary equal to the > > > + * alignment gcc 4.5 uses for a struct > > > + */ > > > +#define STRUCT_ALIGN() . = ALIGN(32) > > > + > > What I'm nervous about is when gcc 4.8 decides to up the alignment to > 64. > > Maybe we should have both patches, just to be safe. Another approach could be to just stop playing games with alignment and use the fact that __stop_syscalls_metadata point to next byte after last entry. Something like the below untested patch. But to fix the current regression I prefer the simpler patch that just fixup the aligment. Sam diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c index 34e3580..50e9606 100644 --- a/kernel/trace/trace_syscalls.c +++ b/kernel/trace/trace_syscalls.c @@ -79,15 +79,19 @@ static struct syscall_metadata *find_syscall_meta(unsigned long syscall) stop = (struct syscall_metadata *)__stop_syscalls_metadata; kallsyms_lookup(syscall, NULL, NULL, NULL, str); - for ( ; start < stop; start++) { + /* + * start may point a few bytes before first entry + * stop points at first byte after last entry + */ + for (stop--; stop >= start; stop--) { /* * Only compare after the "sys" prefix. Archs that use * syscall wrappers may have syscalls symbols aliases prefixed * with "SyS" instead of "sys", leading to an unwanted * mismatch. */ - if (start->name && !strcmp(start->name + 3, str + 3)) - return start; + if (stop->name && !strcmp(stop->name + 3, str + 3)) + return stop; } return NULL; } -- 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/