linux-kernel - Re: 2.6.35 regression

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Date:	Fri, 9 Jul 2010 11:45:09 +0300
From:	Zeev Tarantov <zeev.tarantov@...il.com>
To:	rostedt@...dmis.org
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Maciej Rutecki <maciej.rutecki@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: 2.6.35 regression

On Fri, Jul 9, 2010 at 06:26, Steven Rostedt <rostedt@...dmis.org> wrote:
> On Thu, 2010-07-08 at 21:53 +0300, Zeev Tarantov wrote:
>
>> With gcc 4.5.1 rev. 161655 objdump shows:
>> Disassembly of section .data:
>>
>> ffffffff8173c438 <__start_syscalls_metadata>:
>>         ...
>>
>> ffffffff8173c440 <__syscall_meta__mmap>:
>> ffffffff8173c440:       2b ab 5f 81 ff ff       sub    -0x7ea1(%rbx),%ebp
>
> Yeah, this is definitely the issue. It starts off at ffffffff8173c438,
> when the first item is really at ffffffff8173c440.
>
> Can you try this patch out:
>
> -- Steve
>
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index 7f614ce..13ebb54 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -124,7 +124,8 @@ extern struct trace_event_functions enter_syscall_print_funcs;
>  extern struct trace_event_functions exit_syscall_print_funcs;
>
>  #define SYSCALL_TRACE_ENTER_EVENT(sname)                               \
> -       static struct syscall_metadata __syscall_meta_##sname;          \
> +       static struct syscall_metadata                                  \
> +       __attribute__((__aligned__(4))) __syscall_meta_##sname;         \
>        static struct ftrace_event_call                                 \
>        __attribute__((__aligned__(4))) event_enter_##sname;            \
>        static struct ftrace_event_call __used                          \
> @@ -138,7 +139,8 @@ extern struct trace_event_functions exit_syscall_print_funcs;
>        }
>
>  #define SYSCALL_TRACE_EXIT_EVENT(sname)                                        \
> -       static struct syscall_metadata __syscall_meta_##sname;          \
> +       static struct syscall_metadata                                  \
> +       __attribute__((__aligned__(4))) __syscall_meta_##sname;         \
>        static struct ftrace_event_call                                 \
>        __attribute__((__aligned__(4))) event_exit_##sname;             \
>        static struct ftrace_event_call __used                          \
>
>
>
>

Boots fine with this applied.
Linux version 2.6.35-rc4 (wolf@...fpc) (gcc version 4.5.1-pre9999
20100701 (prerelease) rev. 161655 (Gentoo SVN) ) #5 SMP Fri Jul 9
11:13:08 IDT 2010

I hope Linus accepts this patch as it seems to me the compiler is
doing something it is allowed to do.

Thank you for the prompt response!

-Zeev
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