From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934826Ab0CMB2L (ORCPT ); Fri, 12 Mar 2010 20:28:11 -0500 Received: from kroah.org ([198.145.64.141]:60707 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934900Ab0CMAUE (ORCPT ); Fri, 12 Mar 2010 19:20:04 -0500 X-Mailbox-Line: From gregkh@kvm.kroah.org Fri Mar 12 16:15:08 2010 Message-Id: <20100313001508.767772036@kvm.kroah.org> User-Agent: quilt/0.48-4.4 Date: Fri, 12 Mar 2010 16:12:19 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Jeff Mahoney , Steven Rostedt Subject: [patch 041/123] tracing: Fix ftrace_event_call alignment for use with gcc 4.5 In-Reply-To: <20100313001618.GA9811@kroah.com> In-Reply-To: <20100313001618.GA9811@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.33-stable review patch. If anyone has any objections, please let me know. ----------------- From: Jeff Mahoney commit 86c38a31aa7f2dd6e74a262710bf8ebf7455acc5 upstream. GCC 4.5 introduces behavior that forces the alignment of structures to use the largest possible value. The default value is 32 bytes, so if some structures are defined with a 4-byte alignment and others aren't declared with an alignment constraint at all - it will align at 32-bytes. For things like the ftrace events, this results in a non-standard array. When initializing the ftrace subsystem, we traverse the _ftrace_events section and call the initialization callback for each event. When the structures are misaligned, we could be treating another part of the structure (or the zeroed out space between them) as a function pointer. This patch forces the alignment for all the ftrace_event_call structures to 4 bytes. Without this patch, the kernel fails to boot very early when built with gcc 4.5. It's trivial to check the alignment of the members of the array, so it might be worthwhile to add something to the build system to do that automatically. Unfortunately, that only covers this case. I've asked one of the gcc developers about adding a warning when this condition is seen. Signed-off-by: Jeff Mahoney LKML-Reference: <4B85770B.6010901@suse.com> Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman --- include/linux/syscalls.h | 6 ++++-- include/trace/ftrace.h | 3 ++- kernel/trace/trace.h | 3 ++- 3 files changed, 8 insertions(+), 4 deletions(-) --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -132,7 +132,8 @@ struct perf_event_attr; #define SYSCALL_TRACE_ENTER_EVENT(sname) \ static const struct syscall_metadata __syscall_meta_##sname; \ - static struct ftrace_event_call event_enter_##sname; \ + static struct ftrace_event_call \ + __attribute__((__aligned__(4))) event_enter_##sname; \ static struct trace_event enter_syscall_print_##sname = { \ .trace = print_syscall_enter, \ }; \ @@ -154,7 +155,8 @@ struct perf_event_attr; #define SYSCALL_TRACE_EXIT_EVENT(sname) \ static const struct syscall_metadata __syscall_meta_##sname; \ - static struct ftrace_event_call event_exit_##sname; \ + static struct ftrace_event_call \ + __attribute__((__aligned__(4))) event_exit_##sname; \ static struct trace_event exit_syscall_print_##sname = { \ .trace = print_syscall_exit, \ }; \ --- a/include/trace/ftrace.h +++ b/include/trace/ftrace.h @@ -65,7 +65,8 @@ }; #undef DEFINE_EVENT #define DEFINE_EVENT(template, name, proto, args) \ - static struct ftrace_event_call event_##name + static struct ftrace_event_call \ + __attribute__((__aligned__(4))) event_##name #undef DEFINE_EVENT_PRINT #define DEFINE_EVENT_PRINT(template, name, proto, args, print) \ --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -791,7 +791,8 @@ extern const char *__stop___trace_bprint #undef FTRACE_ENTRY #define FTRACE_ENTRY(call, struct_name, id, tstruct, print) \ - extern struct ftrace_event_call event_##call; + extern struct ftrace_event_call \ + __attribute__((__aligned__(4))) event_##call; #undef FTRACE_ENTRY_DUP #define FTRACE_ENTRY_DUP(call, struct_name, id, tstruct, print) \ FTRACE_ENTRY(call, struct_name, id, PARAMS(tstruct), PARAMS(print))