Re: 2.6.35 regression
From: Zeev Tarantov
Date: Fri Jul 09 2010 - 04:45:37 EST
On Fri, Jul 9, 2010 at 06:26, Steven Rostedt <rostedt@xxxxxxxxxxx> 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@wolfpc) (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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