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Re: [PATCH -tip v8 07/26] [BUGFIX] x86: Prohibit probing on thunk functions and restore
- From: Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>
- To: Steven Rostedt <rostedt at goodmis dot org>
- Cc: linux-kernel at vger dot kernel dot org, Ingo Molnar <mingo at kernel dot org>, Andi Kleen <andi at firstfloor dot org>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Sandeepa Prabhu <sandeepa dot prabhu at linaro dot org>, Frederic Weisbecker <fweisbec at gmail dot com>, x86 at kernel dot org, fche at redhat dot com, mingo at redhat dot com, systemtap at sourceware dot org, "H. Peter Anvin" <hpa at zytor dot com>, Thomas Gleixner <tglx at linutronix dot de>
- Date: Mon, 24 Mar 2014 12:03:57 +0900
- Subject: Re: [PATCH -tip v8 07/26] [BUGFIX] x86: Prohibit probing on thunk functions and restore
- Authentication-results: sourceware.org; auth=none
- References: <20140305115843 dot 22766 dot 8355 dot stgit at ltc230 dot yrl dot intra dot hitachi dot co dot jp> <20140305115932 dot 22766 dot 76074 dot stgit at ltc230 dot yrl dot intra dot hitachi dot co dot jp> <20140321210020 dot 438f6e32 at gandalf dot local dot home>
(2014/03/22 10:00), Steven Rostedt wrote:
> On Wed, 05 Mar 2014 20:59:32 +0900
> Masami Hiramatsu <masami.hiramatsu.pt@hitachi.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@hitachi.com