linux-kernel - Re: [PATCH -tip v8 07/26] [BUGFIX] x86: Prohibit probing on thunk functions and restore

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Message-ID: <532FA09D.1040405@hitachi.com>
Date:	Mon, 24 Mar 2014 12:03:57 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Andi Kleen <andi@...stfloor.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Sandeepa Prabhu <sandeepa.prabhu@...aro.org>,
	Frederic Weisbecker <fweisbec@...il.com>, x86@...nel.org,
	fche@...hat.com, mingo@...hat.com, systemtap@...rceware.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH -tip v8 07/26] [BUGFIX] x86: Prohibit probing on thunk
 functions and restore

(2014/03/22 10:00), Steven Rostedt wrote:
> On Wed, 05 Mar 2014 20:59:32 +0900
> Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> wrote:
> 
>>  	thunk_ra trace_hardirqs_on_thunk,trace_hardirqs_on_caller
>> diff --git a/arch/x86/lib/thunk_64.S b/arch/x86/lib/thunk_64.S
>> index a63efd6..92d9fea 100644
>> --- a/arch/x86/lib/thunk_64.S
>> +++ b/arch/x86/lib/thunk_64.S
>> @@ -8,6 +8,7 @@
>>  #include <linux/linkage.h>
>>  #include <asm/dwarf2.h>
>>  #include <asm/calling.h>
>> +#include <asm/asm.h>
>>  
>>  	/* rdi:	arg1 ... normal C conventions. rax is saved/restored. */
>>  	.macro THUNK name, func, put_ret_addr_in_rdi=0
>> @@ -25,6 +26,7 @@
>>  	call \func
>>  	jmp  restore
>>  	CFI_ENDPROC
>> +	_ASM_NOKPROBE(\name)
>>  	.endm
>>  
>>  #ifdef CONFIG_TRACE_IRQFLAGS
>> @@ -43,3 +45,4 @@ restore:
>>  	RESTORE_ARGS
>>  	ret
>>  	CFI_ENDPROC
>> +	_ASM_NOKPROBE(restore)
>>
> 
> Does kallsyms return something for this? I'm curious to what it does.
> It might find something that we didn't expect. Do you have debug code
> to list out all the black listed items found at boot up?

Yes, with [19/26] the blacklisted functions are shown in debugfs
(kprobes/blacklist) :)

Thank you,

-- 
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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