From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D09BC2564 for ; Wed, 18 Jan 2023 07:17:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 84667C433F2 for ; Wed, 18 Jan 2023 07:17:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1674026232; bh=kmI23F6YpP3wP+g6JxGd9ZmFmajQvU1haCUNlhO3JMw=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=IKAFn5uTcg+8TtVkywsk3Sfdgh218KJjHAOtNH61GBkSXJkYhsFJgkCvmdkkjJaJE jIKlUtyS9GCuUeAYRbkYeV8E9TmSqxkHk+duZKEymJl8Ik01QKAh9yH0m5K63d1lts 6QjZnFsRRY+PIN43IuhYpp1VXkw8HlC8CKJOmFmyk74R7poDsvq9XojRQijqNB33RQ 7jqI1+0U4HtZp7BGOFjsCCdEigHReSb75PpXi4MbwFEnbFaSBO1BcPBo2Q9YEFrYUz dPbQd99tfvdfN2Cik+QnAFEFN3G/+YuPMKzaxmJDmVD2NXslariAeFFFvNR0Uxxlct dF/7XjyvOC8Ow== Received: by mail-ej1-f49.google.com with SMTP id qx13so22592212ejb.13 for ; Tue, 17 Jan 2023 23:17:12 -0800 (PST) X-Gm-Message-State: AFqh2krTRkCRxXG7o+XwDVtWJh9T/PZWgUCVGTvVYoXqYbH3LXNnYjyK MNohqOC/wVdqhe94GYCvWOc2Ylv3/DPeeLNLIVw= X-Google-Smtp-Source: AMrXdXvw3gfeEzkqEdPNf8APUQ9AeGM5NX4sydYdm5mAAml2mXeWFM9jEmlnJQaCbiXRL/ZwaKYwQWpkjcxm8fUlNXc= X-Received: by 2002:a17:906:f86:b0:7b2:7e7a:11c1 with SMTP id q6-20020a1709060f8600b007b27e7a11c1mr511388ejj.684.1674026230719; Tue, 17 Jan 2023 23:17:10 -0800 (PST) Precedence: bulk X-Mailing-List: loongarch@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <1674007261-9198-1-git-send-email-yangtiezhu@loongson.cn> <1674007261-9198-5-git-send-email-yangtiezhu@loongson.cn> <48f0508f-3908-c6ca-c8ba-7c12dd6b3f11@loongson.cn> <7f518dec-fd72-a73c-3f23-6372a83d65c2@loongson.cn> <6879b948-2d61-8e09-a9d4-bc2ede31c52b@loongson.cn> In-Reply-To: <6879b948-2d61-8e09-a9d4-bc2ede31c52b@loongson.cn> From: Huacai Chen Date: Wed, 18 Jan 2023 15:17:00 +0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v12 4/5] LoongArch: Mark some assembler symbols as non-kprobe-able To: Tiezhu Yang Cc: Jinyang He , WANG Xuerui , Masami Hiramatsu , loongarch@lists.linux.dev, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" On Wed, Jan 18, 2023 at 2:24 PM Tiezhu Yang wrote: > > > > On 01/18/2023 02:05 PM, Jinyang He wrote: > > > > On 2023-01-18 12:23, Tiezhu Yang wrote: > >> > >> > >> On 01/18/2023 12:14 PM, Huacai Chen wrote: > >>> If memcpy should be blacklisted, then what about memset and memmove? > >> > >> According to the test results, there are no problems to probe > >> memset and memmove, so no need to blacklist them for now, > >> blacklist memcpy is because it may cause recursive exceptions, > >> there is a detailed discussion in the following link: > >> > >> https://lore.kernel.org/lkml/20230114143859.7ccc45c1c5d9ce302113ab0a@kernel.org/ > >> > > > > Hi, Tiezhu, > > > > I cannot reproduce the results when kprobe memcpy. Could you please give > > some details. Emm, I just replace "kernel_clone" with "memcpy" in > > kprobe_example.c. > > Please remove the related "_ASM_NOKPROBE(memcpy)" code in > arch/loongarch/lib/memcpy.S, and then compile and update kernel, > execute the following cmd after reboot, I can reproduce the hang > problem easily (it will take a few minutes). > > modprobe kprobe_example symbol="memcpy" Then, why is handle_syscall different from other exception handlers? Huacai > > > > > And for your call trace, > > > > handler_pre() > > pr_info() > > printk() > > _printk() > > vprintk() > > vprintk_store() > > memcpy() > > > > I think when we should skip this time kprobe which triggered in > > handler_{pre, post}. That means this time kprobe will not call > > handler_{pre, post} agian, and not cause recursion. I remember > > your codes had done this skip action. So, that's so strange if > > recursion in handler_{pre, post}. > > > > > > Thanks, > > > > Jinyang > > > > > >> > >> Thanks, > >> Tiezhu > >> > >>> > >>> Huacai > >>> > >>> On Wed, Jan 18, 2023 at 10:01 AM Tiezhu Yang > >>> wrote: > >>>> > >>>> Some assembler symbols are not kprobe safe, such as handle_syscall > >>>> (used as syscall exception handler), *memcpy* (may cause recursive > >>>> exceptions), they can not be instrumented, just blacklist them for > >>>> kprobing. > >>>> > >>>> Here is a related problem and discussion: > >>>> Link: > >>>> https://lore.kernel.org/lkml/20230114143859.7ccc45c1c5d9ce302113ab0a@kernel.org/ > >>>> > >>>> > >>>> Signed-off-by: Tiezhu Yang > >>>> --- > >>>> arch/loongarch/include/asm/asm.h | 10 ++++++++++ > >>>> arch/loongarch/kernel/entry.S | 1 + > >>>> arch/loongarch/lib/memcpy.S | 3 +++ > >>>> 3 files changed, 14 insertions(+) > >>>> > >>>> diff --git a/arch/loongarch/include/asm/asm.h > >>>> b/arch/loongarch/include/asm/asm.h > >>>> index 40eea6a..f591b32 100644 > >>>> --- a/arch/loongarch/include/asm/asm.h > >>>> +++ b/arch/loongarch/include/asm/asm.h > >>>> @@ -188,4 +188,14 @@ > >>>> #define PTRLOG 3 > >>>> #endif > >>>> > >>>> +/* Annotate a function as being unsuitable for kprobes. */ > >>>> +#ifdef CONFIG_KPROBES > >>>> +#define _ASM_NOKPROBE(name) \ > >>>> + .pushsection "_kprobe_blacklist", "aw"; \ > >>>> + .quad name; \ > >>>> + .popsection > >>>> +#else > >>>> +#define _ASM_NOKPROBE(name) > >>>> +#endif > >>>> + > >>>> #endif /* __ASM_ASM_H */ > >>>> diff --git a/arch/loongarch/kernel/entry.S > >>>> b/arch/loongarch/kernel/entry.S > >>>> index d53b631..55e23b1 100644 > >>>> --- a/arch/loongarch/kernel/entry.S > >>>> +++ b/arch/loongarch/kernel/entry.S > >>>> @@ -67,6 +67,7 @@ SYM_FUNC_START(handle_syscall) > >>>> > >>>> RESTORE_ALL_AND_RET > >>>> SYM_FUNC_END(handle_syscall) > >>>> +_ASM_NOKPROBE(handle_syscall) > >>>> > >>>> SYM_CODE_START(ret_from_fork) > >>>> bl schedule_tail # a0 = struct task_struct *prev > >>>> diff --git a/arch/loongarch/lib/memcpy.S b/arch/loongarch/lib/memcpy.S > >>>> index 7c07d59..3b7e1de 100644 > >>>> --- a/arch/loongarch/lib/memcpy.S > >>>> +++ b/arch/loongarch/lib/memcpy.S > >>>> @@ -17,6 +17,7 @@ SYM_FUNC_START(memcpy) > >>>> ALTERNATIVE "b __memcpy_generic", \ > >>>> "b __memcpy_fast", CPU_FEATURE_UAL > >>>> SYM_FUNC_END(memcpy) > >>>> +_ASM_NOKPROBE(memcpy) > >>>> > >>>> EXPORT_SYMBOL(memcpy) > >>>> > >>>> @@ -41,6 +42,7 @@ SYM_FUNC_START(__memcpy_generic) > >>>> 2: move a0, a3 > >>>> jr ra > >>>> SYM_FUNC_END(__memcpy_generic) > >>>> +_ASM_NOKPROBE(__memcpy_generic) > >>>> > >>>> /* > >>>> * void *__memcpy_fast(void *dst, const void *src, size_t n) > >>>> @@ -93,3 +95,4 @@ SYM_FUNC_START(__memcpy_fast) > >>>> 3: move a0, a3 > >>>> jr ra > >>>> SYM_FUNC_END(__memcpy_fast) > >>>> +_ASM_NOKPROBE(__memcpy_fast) > >>>> -- > >>>> 2.1.0 > >>>> > >> > >