From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
LKML <linux-kernel@vger.kernel.org>,
Rusty Russell <rusty@rustcorp.com.au>,
seiji.aguchi@hds.com, Jiri Kosina <jkosina@suse.cz>,
Kees Cook <keescook@chromium.org>,
Andrew Morton <akpm@linux-foundation.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@suse.de>,
linux-tip-commits@vger.kernel.org
Subject: Re: Re: [tip:perf/kprobes] kprobes, x86: Call exception_enter after kprobes handled
Date: Sat, 14 Jun 2014 14:44:18 +0900 [thread overview]
Message-ID: <539BE132.2080008@hitachi.com> (raw)
In-Reply-To: <CAFTL4hyYa7=h3DE+kkpNpWxp4VtaJ07tkkj96W+ZAmKtZD+pkA@mail.gmail.com>
Hi Frederic,
(2014/06/14 2:14), Frederic Weisbecker wrote:
> Hi Masami,
>
> 2014-04-24 12:59 GMT+02:00 tip-bot for Masami Hiramatsu <tipbot@zytor.com>:
>> Commit-ID: ecd50f714c421c759354632dd00f70c718c95b10
>> Gitweb: http://git.kernel.org/tip/ecd50f714c421c759354632dd00f70c718c95b10
>> Author: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
>> AuthorDate: Thu, 17 Apr 2014 17:17:40 +0900
>> Committer: Ingo Molnar <mingo@kernel.org>
>> CommitDate: Thu, 24 Apr 2014 10:03:00 +0200
>>
>> kprobes, x86: Call exception_enter after kprobes handled
>>
>> Move exception_enter() call after kprobes handler
>> is done. Since the exception_enter() involves
>> many other functions (like printk), it can cause
>> recursive int3/break loop when kprobes probe such
>> functions.
>>
>> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
>> Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Borislav Petkov <bp@suse.de>
>> Cc: Jiri Kosina <jkosina@suse.cz>
>> Cc: Kees Cook <keescook@chromium.org>
>> Cc: Rusty Russell <rusty@rustcorp.com.au>
>> Cc: Seiji Aguchi <seiji.aguchi@hds.com>
>> Link: http://lkml.kernel.org/r/20140417081740.26341.10894.stgit@ltc230.yrl.intra.hitachi.co.jp
>> Signed-off-by: Ingo Molnar <mingo@kernel.org>
>
> This patch results in exception_enter/exception_exit imbalances:
>
> arch/x86/kernel/traps.c: In function ‘do_debug’:
> include/linux/context_tracking.h:46:6: warning: ‘prev_state’ may be
> used uninitialized in this function [-Wmaybe-uninitialized]
> if (prev_ctx == IN_USER)
> ^
> arch/x86/kernel/traps.c:431:17: note: ‘prev_state’ was declared here
> enum ctx_state prev_state;
Oops, obviously there are bugs...
> An obvious solution would be to change all the goto exit before
> exception_enter() to return from do_debug(). But if there are any user
> of RCU before exception_enter() this won't work. Does
> kprobe_debug_andle() use RCU read side critical sections? I'm also
> worried about kmemcheck...
As far as I can check the code again, it is enough to remove this patch and
to add context_track_user_*() to kprobe blacklist, since those checks
in_interrupt() at the entry and returns immediately. It seems
we have no problem on it. I think that was my fault. :(
I'll send a bugfix, thank you!
>
>> ---
>> arch/x86/kernel/traps.c | 5 ++---
>> 1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
>> index e5d4a70..ba9abe9 100644
>> --- a/arch/x86/kernel/traps.c
>> +++ b/arch/x86/kernel/traps.c
>> @@ -327,7 +327,6 @@ dotraplinkage void __kprobes notrace do_int3(struct pt_regs *regs, long error_co
>> if (poke_int3_handler(regs))
>> return;
>>
>> - prev_state = exception_enter();
>> #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
>> if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,
>> SIGTRAP) == NOTIFY_STOP)
>> @@ -338,6 +337,7 @@ dotraplinkage void __kprobes notrace do_int3(struct pt_regs *regs, long error_co
>> if (kprobe_int3_handler(regs))
>> return;
>> #endif
>> + prev_state = exception_enter();
>>
>> if (notify_die(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,
>> SIGTRAP) == NOTIFY_STOP)
>> @@ -415,8 +415,6 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
>> unsigned long dr6;
>> int si_code;
>>
>> - prev_state = exception_enter();
>> -
>> get_debugreg(dr6, 6);
>>
>> /* Filter out all the reserved bits which are preset to 1 */
>> @@ -449,6 +447,7 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
>> if (kprobe_debug_handler(regs))
>> goto exit;
>> #endif
>> + prev_state = exception_enter();
>>
>> if (notify_die(DIE_DEBUG, "debug", regs, (long)&dr6, error_code,
>> SIGTRAP) == NOTIFY_STOP)
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
>
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com
next prev parent reply other threads:[~2014-06-14 5:44 UTC|newest]
Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-17 8:16 [PATCH -tip v9 00/26] kprobes: introduce NOKPROBE_SYMBOL, bugfixes and scalbility efforts Masami Hiramatsu
2014-04-17 8:16 ` [PATCH -tip v9 01/26] [BUGFIX]kprobes/x86: Fix page-fault handling logic Masami Hiramatsu
2014-04-17 9:58 ` [tip:perf/urgent] kprobes/x86: " tip-bot for Masami Hiramatsu
2014-04-17 8:16 ` [PATCH -tip v9 02/26] kprobes/x86: Allow to handle reentered kprobe on singlestepping Masami Hiramatsu
2014-04-24 10:57 ` [tip:perf/kprobes] kprobes/x86: Allow to handle reentered kprobe on single-stepping tip-bot for Masami Hiramatsu
2014-04-17 8:16 ` [PATCH -tip v9 03/26] kprobes: Prohibit probing on .entry.text code Masami Hiramatsu
2014-04-24 10:57 ` [tip:perf/kprobes] " tip-bot for Masami Hiramatsu
2014-04-17 8:17 ` [PATCH -tip v9 04/26] kprobes: Introduce NOKPROBE_SYMBOL() macro for blacklist Masami Hiramatsu
2014-04-24 10:58 ` [tip:perf/kprobes] kprobes: Introduce NOKPROBE_SYMBOL() macro to maintain kprobes blacklist tip-bot for Masami Hiramatsu
2014-05-01 5:26 ` kprobes broken in linux-next (was Re: [tip:perf/kprobes] kprobes: Introduce NOKPROBE_SYMBOL() macro to maintain kprobes blacklist) Vineet Gupta
2014-05-02 1:13 ` Masami Hiramatsu
2014-05-07 4:56 ` Vineet Gupta
2014-05-07 19:18 ` [tip:perf/kprobes] kprobes: Ensure blacklist data is aligned tip-bot for Vineet Gupta
2014-05-05 20:48 ` [tip:perf/kprobes] kprobes: Introduce NOKPROBE_SYMBOL() macro to maintain kprobes blacklist Tony Luck
2014-05-06 9:25 ` Masami Hiramatsu
2014-05-06 10:03 ` Masami Hiramatsu
2014-05-07 11:19 ` Masami Hiramatsu
2014-05-07 11:55 ` [RFT PATCH -next ] [BUGFIX] kprobes: Fix "Failed to find blacklist" error on ia64 and ppc64 Masami Hiramatsu
2014-05-07 11:59 ` Masami Hiramatsu
2014-05-14 8:19 ` Masami Hiramatsu
2014-05-08 4:47 ` Ananth N Mavinakayanahalli
2014-05-08 5:40 ` Masami Hiramatsu
2014-05-08 6:16 ` Ananth N Mavinakayanahalli
2014-05-09 8:06 ` Masami Hiramatsu
2014-05-26 11:25 ` Suzuki K. Poulose
2014-05-26 11:48 ` Masami Hiramatsu
2014-05-27 6:31 ` [RFT PATCH -next v2] " Masami Hiramatsu
2014-05-29 19:13 ` Suzuki K. Poulose
2014-05-30 2:47 ` Masami Hiramatsu
2014-05-30 3:18 ` [RFT PATCH -next v3] " Masami Hiramatsu
2014-06-06 6:38 ` Masami Hiramatsu
2014-06-17 23:03 ` Tony Luck
2014-06-18 7:56 ` Michael Ellerman
2014-06-18 8:46 ` Masami Hiramatsu
2014-06-19 1:30 ` Michael Ellerman
2014-06-19 4:52 ` Masami Hiramatsu
2014-06-19 6:40 ` Suzuki K. Poulose
2014-06-19 7:26 ` Masami Hiramatsu
2014-06-19 9:45 ` Suzuki K. Poulose
2014-06-19 11:01 ` Masami Hiramatsu
2014-06-19 11:20 ` Masami Hiramatsu
2014-06-20 0:37 ` Michael Ellerman
2014-06-20 2:13 ` Masami Hiramatsu
2014-04-17 8:17 ` [PATCH -tip v9 05/26] [BUGFIX] kprobes/x86: Prohibit probing on debug_stack_* Masami Hiramatsu
2014-04-24 10:58 ` [tip:perf/kprobes] kprobes, x86: Prohibit probing on debug_stack_*() tip-bot for Masami Hiramatsu
2014-04-17 8:17 ` [PATCH -tip v9 06/26] [BUGFIX] x86: Prohibit probing on native_set_debugreg/load_idt Masami Hiramatsu
2014-04-24 10:58 ` [tip:perf/kprobes] kprobes, x86: Prohibit probing on native_set_debugreg()/load_idt() tip-bot for Masami Hiramatsu
2014-04-17 8:17 ` [PATCH -tip v9 07/26] [BUGFIX] x86: Prohibit probing on thunk functions and restore Masami Hiramatsu
2014-04-24 10:58 ` [tip:perf/kprobes] kprobes, " tip-bot for Masami Hiramatsu
2014-04-17 8:17 ` [PATCH -tip v9 08/26] kprobes/x86: Call exception handlers directly from do_int3/do_debug Masami Hiramatsu
2014-04-24 10:59 ` [tip:perf/kprobes] " tip-bot for Masami Hiramatsu
2014-04-24 11:26 ` Jiri Kosina
2014-04-17 8:17 ` [PATCH -tip v9 09/26] x86: Call exception_enter after kprobes handled Masami Hiramatsu
2014-04-24 10:59 ` [tip:perf/kprobes] kprobes, " tip-bot for Masami Hiramatsu
2014-06-13 17:14 ` Frederic Weisbecker
2014-06-14 5:44 ` Masami Hiramatsu [this message]
2014-06-14 6:47 ` [PATCH -tip ] [Bugfix] x86/kprobes: Fix build errors and blacklist context_track_user Masami Hiramatsu
2014-06-14 8:58 ` [tip:perf/urgent] " tip-bot for Masami Hiramatsu
2014-06-16 15:52 ` [PATCH -tip ] [Bugfix] " Frederic Weisbecker
2014-04-17 8:17 ` [PATCH -tip v9 10/26] kprobes/x86: Allow probe on some kprobe preparation functions Masami Hiramatsu
2014-04-24 10:59 ` [tip:perf/kprobes] " tip-bot for Masami Hiramatsu
2014-04-17 8:17 ` [PATCH -tip v9 11/26] kprobes: Allow probe on some kprobe functions Masami Hiramatsu
2014-04-24 10:59 ` [tip:perf/kprobes] " tip-bot for Masami Hiramatsu
2014-04-17 8:18 ` [PATCH -tip v9 12/26] ftrace/*probes: Allow probing on some functions Masami Hiramatsu
2014-04-24 10:59 ` [tip:perf/kprobes] kprobes, ftrace: " tip-bot for Masami Hiramatsu
2014-04-17 8:18 ` [PATCH -tip v9 13/26] x86: Allow kprobes on text_poke/hw_breakpoint Masami Hiramatsu
2014-04-24 11:00 ` [tip:perf/kprobes] kprobes, x86: Allow kprobes on text_poke/ hw_breakpoint tip-bot for Masami Hiramatsu
2014-04-24 11:26 ` Jiri Kosina
2014-04-17 8:18 ` [PATCH -tip v9 14/26] x86: Use NOKPROBE_SYMBOL() instead of __kprobes annotation Masami Hiramatsu
2014-04-24 11:00 ` [tip:perf/kprobes] kprobes, " tip-bot for Masami Hiramatsu
2014-04-17 8:18 ` [PATCH -tip v9 15/26] kprobes: Use NOKPROBE_SYMBOL macro instead of __kprobes Masami Hiramatsu
2014-04-24 11:00 ` [tip:perf/kprobes] " tip-bot for Masami Hiramatsu
2014-04-17 8:18 ` [PATCH -tip v9 16/26] ftrace/kprobes: Use NOKPROBE_SYMBOL macro in ftrace Masami Hiramatsu
2014-04-24 11:00 ` [tip:perf/kprobes] kprobes, ftrace: " tip-bot for Masami Hiramatsu
2014-04-17 8:18 ` [PATCH -tip v9 17/26] notifier: Use NOKPROBE_SYMBOL macro in notifier Masami Hiramatsu
2014-04-17 14:40 ` Josh Triplett
2014-04-24 11:00 ` [tip:perf/kprobes] kprobes, " tip-bot for Masami Hiramatsu
2014-04-17 8:18 ` [PATCH -tip v9 18/26] sched: Use NOKPROBE_SYMBOL macro in sched Masami Hiramatsu
2014-04-24 11:01 ` [tip:perf/kprobes] kprobes, " tip-bot for Masami Hiramatsu
2014-04-17 8:18 ` [PATCH -tip v9 19/26] kprobes: Show blacklist entries via debugfs Masami Hiramatsu
2014-04-24 11:01 ` [tip:perf/kprobes] " tip-bot for Masami Hiramatsu
2014-04-17 8:18 ` [PATCH -tip v9 20/26] kprobes: Support blacklist functions in module Masami Hiramatsu
2014-04-24 8:56 ` Ingo Molnar
2014-04-24 11:24 ` Masami Hiramatsu
2014-04-25 8:19 ` Ingo Molnar
2014-04-25 10:12 ` Masami Hiramatsu
2014-04-25 10:55 ` Masami Hiramatsu
2014-04-17 8:19 ` [PATCH -tip v9 21/26] kprobes: Use NOKPROBE_SYMBOL() in sample modules Masami Hiramatsu
2014-04-17 8:19 ` [PATCH -tip v9 22/26] kprobes/x86: Use kprobe_blacklist for .kprobes.text and .entry.text Masami Hiramatsu
2014-04-24 8:58 ` Ingo Molnar
2014-04-24 11:22 ` Masami Hiramatsu
2014-04-17 8:19 ` [PATCH -tip v9 23/26] kprobes/x86: Remove unneeded preempt_disable/enable in interrupt handlers Masami Hiramatsu
2014-04-17 8:19 ` [PATCH -tip v9 24/26] kprobes: Enlarge hash table to 512 entries Masami Hiramatsu
2014-04-17 8:19 ` [PATCH -tip v9 25/26] kprobes: Introduce kprobe cache to reduce cache misshits Masami Hiramatsu
2014-04-24 9:01 ` Ingo Molnar
2014-04-24 11:38 ` Masami Hiramatsu
2014-04-25 8:20 ` Ingo Molnar
2014-04-25 9:43 ` Masami Hiramatsu
2014-04-26 7:12 ` Ingo Molnar
2014-04-27 12:49 ` Masami Hiramatsu
2014-04-17 8:19 ` [PATCH -tip v9 26/26] ftrace: Introduce FTRACE_OPS_FL_SELF_FILTER for ftrace-kprobe Masami Hiramatsu
2014-04-17 8:37 ` [PATCH -tip v9 00/26] kprobes: introduce NOKPROBE_SYMBOL, bugfixes and scalbility efforts Ingo Molnar
2014-04-17 8:53 ` Masami Hiramatsu
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