From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) (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 AA62212E40; Wed, 20 Mar 2024 03:30:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.189 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710905430; cv=none; b=Mxu6yYSyUiES8UvBKp9sFnB14mNjLD0UWvsO1UULHGOv0nA65kxmX4c5CjB3HwQqqvO3mxqDvHx+3coZvlHKdWNdjl0H9ntUNMTEw/QgDp3/6IqY0RRSCuD7zzdGxpvjmgfmNwsXjl5WMOeFzqrCRxE51PRjSjrJwaIebW1dVZ8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710905430; c=relaxed/simple; bh=wNIYr0YRIvV7+ACKzGHG2nKgc76mfD09xmnyWCrTk0w=; h=Subject:To:References:CC:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=hWovm4NmRTSu+YYvyVcmp4yNRWjgOljKfuEtlNDxoBW6xbIekXPdCmdpETtKUkfmHTgBhWDE2S2f9XD/SDPR/nwkVV7BlcVZTfbpxq9BuRs2YyEI1qgA9MyuPPnwBRsTri6QwND7r9pjGSMpYBBKfVNHWlzPV73ulANM3qk9GZQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.189 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.88.105]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4TzvF56Y93zNmFg; Wed, 20 Mar 2024 11:28:25 +0800 (CST) Received: from canpemm500010.china.huawei.com (unknown [7.192.105.118]) by mail.maildlp.com (Postfix) with ESMTPS id DE0BF140487; Wed, 20 Mar 2024 11:30:18 +0800 (CST) Received: from [10.67.111.82] (10.67.111.82) by canpemm500010.china.huawei.com (7.192.105.118) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.35; Wed, 20 Mar 2024 11:30:18 +0800 Subject: Re: [PATCH] ARM: unwind: improve unwinders for noreturn case To: Kees Cook References: <1709516385-7778-1-git-send-email-xiaojiangfeng@huawei.com> <1710901169-22763-1-git-send-email-xiaojiangfeng@huawei.com> <202403191945.661DBCE8@keescook> CC: , , , , , , , , , , , , , , , , , , , , , , From: Jiangfeng Xiao Message-ID: Date: Wed, 20 Mar 2024 11:30:13 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <202403191945.661DBCE8@keescook> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500010.china.huawei.com (7.192.105.118) On 2024/3/20 10:46, Kees Cook wrote: > On Wed, Mar 20, 2024 at 10:19:29AM +0800, Jiangfeng Xiao wrote: >> This is an off-by-one bug which is common in unwinders, >> due to the fact that the address on the stack points >> to the return address rather than the call address. >> >> So, for example, when the last instruction of a function >> is a function call (e.g., to a noreturn function), it can >> cause the unwinder to incorrectly try to unwind from >> the function after the callee. >> >> foo: >> ... >> bl bar >> ... end of function and thus next function ... >> >> which results in LR pointing into the next function. >> >> Fixed this by subtracting 1 from frmae->pc in the call frame >> (but not exception frames) like ORC on x86 does. >> >> Refer to the unwind_next_frame function in the unwind_orc.c >> >> Suggested-by: Josh Poimboeuf >> Link: https://lkml.kernel.org/lkml/20240305175846.qnyiru7uaa7itqba@treble/ >> Signed-off-by: Jiangfeng Xiao >> --- >> arch/arm/include/asm/stacktrace.h | 4 ---- >> arch/arm/kernel/stacktrace.c | 2 -- >> arch/arm/kernel/traps.c | 4 ++-- >> arch/arm/kernel/unwind.c | 18 +++++++++++++++--- >> 4 files changed, 17 insertions(+), 11 deletions(-) >> >> diff --git a/arch/arm/include/asm/stacktrace.h b/arch/arm/include/asm/stacktrace.h >> index 360f0d2..07e4c16 100644 >> --- a/arch/arm/include/asm/stacktrace.h >> +++ b/arch/arm/include/asm/stacktrace.h >> @@ -21,9 +21,7 @@ struct stackframe { >> struct llist_node *kr_cur; >> struct task_struct *tsk; >> #endif >> -#ifdef CONFIG_UNWINDER_FRAME_POINTER >> bool ex_frame; >> -#endif >> }; >> >> static __always_inline >> @@ -37,9 +35,7 @@ void arm_get_current_stackframe(struct pt_regs *regs, struct stackframe *frame) >> frame->kr_cur = NULL; >> frame->tsk = current; >> #endif >> -#ifdef CONFIG_UNWINDER_FRAME_POINTER >> frame->ex_frame = in_entry_text(frame->pc); >> -#endif >> } >> >> extern int unwind_frame(struct stackframe *frame); >> diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c >> index 620aa82..1abd4f9 100644 >> --- a/arch/arm/kernel/stacktrace.c >> +++ b/arch/arm/kernel/stacktrace.c >> @@ -154,9 +154,7 @@ static void start_stack_trace(struct stackframe *frame, struct task_struct *task >> frame->kr_cur = NULL; >> frame->tsk = task; >> #endif >> -#ifdef CONFIG_UNWINDER_FRAME_POINTER >> frame->ex_frame = in_entry_text(frame->pc); >> -#endif >> } >> >> void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie, >> diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c >> index 3bad79d..b64e442 100644 >> --- a/arch/arm/kernel/traps.c >> +++ b/arch/arm/kernel/traps.c >> @@ -84,10 +84,10 @@ void dump_backtrace_entry(unsigned long where, unsigned long from, >> printk("%sFunction entered at [<%08lx>] from [<%08lx>]\n", >> loglvl, where, from); >> #elif defined CONFIG_BACKTRACE_VERBOSE >> - printk("%s[<%08lx>] (%ps) from [<%08lx>] (%pS)\n", >> + pr_warn("%s[<%08lx>] (%ps) from [<%08lx>] (%pB)\n", >> loglvl, where, (void *)where, from, (void *)from); > > This should stay printk("%s...", loglvl, ...) or loglvl should be > dropped when converting to pr_warn(): > > pr_warn([<%08lx>] (%ps) from [<%08lx>] (%pB)\n", > where, (void *)where, from, (void *)from); > > Why did you want to force the "warn" log level? > Thank you for your review. I think I'm wrong. The checkpatch.pl script reports the "WARNING: printk() should include KERN_ facility level" warning. That's why I changed printk to pr_warn. I should change printk to printk(KERN_DEFAULT). >> #else >> - printk("%s %ps from %pS\n", loglvl, (void *)where, (void *)from); >> + pr_warn("%s %ps from %pB\n", loglvl, (void *)where, (void *)from); > > Ditto. > > -Kees >