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Re: [PATCH -tip v8 04/26] kprobes: Introduce NOKPROBE_SYMBOL() macro for blacklist
- 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>, Jeremy Fitzhardinge <jeremy at goop dot org>, x86 at kernel dot org, Andi Kleen <andi at firstfloor dot org>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Arnd Bergmann <arnd at arndb dot de>, Peter Zijlstra <peterz at infradead dot org>, Frederic Weisbecker <fweisbec at gmail dot com>, Rusty Russell <rusty at rustcorp dot com dot au>, "David S. Miller" <davem at davemloft dot net>, Chris Wright <chrisw at sous-sol dot org>, Sandeepa Prabhu <sandeepa dot prabhu at linaro dot org>, fche at redhat dot com, mingo at redhat dot com, Rob Landley <rob at landley dot net>, "H. Peter Anvin" <hpa at zytor dot com>, Thomas Gleixner <tglx at linutronix dot de>, Alok Kataria <akataria at vmware dot com>, systemtap at sourceware dot org
- Date: Wed, 26 Mar 2014 16:04:01 +0900
- Subject: Re: [PATCH -tip v8 04/26] kprobes: Introduce NOKPROBE_SYMBOL() macro for blacklist
- 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> <20140305115911 dot 22766 dot 61140 dot stgit at ltc230 dot yrl dot intra dot hitachi dot co dot jp> <20140321204917 dot 636820fa at gandalf dot local dot home>
(2014/03/22 9:49), Steven Rostedt wrote:
> On Wed, 05 Mar 2014 20:59:11 +0900
> Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> wrote:
>
>
>>
>> diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt
>> index 0cfb00f..7062631 100644
>> --- a/Documentation/kprobes.txt
>> +++ b/Documentation/kprobes.txt
>> @@ -22,8 +22,9 @@ Appendix B: The kprobes sysctl interface
>>
>> Kprobes enables you to dynamically break into any kernel routine and
>> collect debugging and performance information non-disruptively. You
>> -can trap at almost any kernel code address, specifying a handler
>> +can trap at almost any kernel code address(*), specifying a handler
>> routine to be invoked when the breakpoint is hit.
>> +(*: at some part of kernel code can not be trapped, see 1.5 Blacklist)
>
> "*: some parts of the kernel code can not be trapped,"
>
>>
>> There are currently three types of probes: kprobes, jprobes, and
>> kretprobes (also called return probes). A kprobe can be inserted
>> @@ -273,6 +274,19 @@ using one of the following techniques:
>> or
>> - Execute 'sysctl -w debug.kprobes_optimization=n'
>>
>> +1.5 Blacklist
>> +
>> +Kprobes can probe almost of the kernel except itself. This means
>
> s/almost/most/
>
>> +that there are some functions where kprobes cannot probe. Probing
>> +(trapping) such functions can cause recursive trap (e.g. double
>
> cause a recursive trap
>
>> +fault) or at least the nested probe handler never be called.
>
> "or the nested probe handler may never be called."
>
>> +Kprobes manages such functions as a blacklist.
>> +If you want to add a function into the blacklist, you just need
>> +to (1) include linux/kprobes.h and (2) use NOKPROBE_SYMBOL() macro
>> +to specify a blacklisted function.
>> +Kprobes checks given probe address with the blacklist and reject
>
> "checks the given probe address against the black list and rejects"
>
>> +registering if the given address is in the blacklist.
>
> registering it, if
Thank you for helping ! :)
>> diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
>> index 4582e8e..7730c1c 100644
>> --- a/arch/x86/include/asm/asm.h
>> +++ b/arch/x86/include/asm/asm.h
>> @@ -57,6 +57,12 @@
>> .long (from) - . ; \
>> .long (to) - . + 0x7ffffff0 ; \
>> .popsection
>> +
>> +# define _ASM_NOKPROBE(entry) \
>> + .pushsection "_kprobe_blacklist","aw" ; \
>> + _ASM_ALIGN ; \
>> + _ASM_PTR (entry); \
>> + .popsection
>> #else
>> # define _ASM_EXTABLE(from,to) \
>> " .pushsection \"__ex_table\",\"a\"\n" \
>> @@ -71,6 +77,7 @@
>> " .long (" #from ") - .\n" \
>> " .long (" #to ") - . + 0x7ffffff0\n" \
>> " .popsection\n"
>> +/* For C file, we already have NOKPROBE_SYMBOL macro */
>> #endif
>>
>> #endif /* _ASM_X86_ASM_H */
>> diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
>> index 1b10af8..4c785fd 100644
>> --- a/arch/x86/kernel/paravirt.c
>> +++ b/arch/x86/kernel/paravirt.c
>> @@ -23,6 +23,7 @@
>> #include <linux/efi.h>
>> #include <linux/bcd.h>
>> #include <linux/highmem.h>
>> +#include <linux/kprobes.h>
>>
>> #include <asm/bug.h>
>> #include <asm/paravirt.h>
>> @@ -389,6 +390,9 @@ __visible struct pv_cpu_ops pv_cpu_ops = {
>> .end_context_switch = paravirt_nop,
>> };
>>
>> +/* At this point, native_get_debugreg has real function entry */
>
> "has a real"
OK, I'll fix them all ;)
Thank you,
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com