From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id C0CDA69D3D for ; Fri, 1 Mar 2024 11:24:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709292263; cv=none; b=U2e9ktZo6gYCA1x+Dk48HgGAujWMdZ0tAV7hYz3S5/tL7+J1uul3kVnd+HGTAio0pyDUQekFk6UhqdK25+Zdiy64NNIoLR0t7eEikhqM9FTFTfZm5J8T3wfVZ+NgbeDZlrYAoAjOC+B0enc8fJgGdM1AOiGoYkZF1pXbNWyJrgY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709292263; c=relaxed/simple; bh=NXtVQpQbXjbQ+2nDWsgKqIjl673GUDImuBDZ3hHzKmI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=E2OJSBTggAsuFQPzFrdcPEVKIlISsplo41v+8WrOCIlwvDgvQzvlT3sMuI+xlX+KwYYuRrS3bVOAg06e6UYW/Vrkce/s26DqqBDb96IsJhh7XsIZWs1n7aWm08GiAMJj/eUA1iMFS1tUPJ8oGS32PaofTD+2h4f+9ynw96tdN+8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 58C141FB; Fri, 1 Mar 2024 03:24:58 -0800 (PST) Received: from FVFF77S0Q05N (unknown [10.57.69.134]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AABE63F6C4; Fri, 1 Mar 2024 03:24:18 -0800 (PST) Date: Fri, 1 Mar 2024 11:24:13 +0000 From: Mark Rutland To: Puranjay Mohan , catalin.marinas@arm.com, will@kernel.org Cc: nathan@kernel.org, broonie@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [PATCH] arm64: prohibit probing on arch_kunwind_consume_entry() Message-ID: References: <20240229231620.24846-1-puranjay12@gmail.com> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240229231620.24846-1-puranjay12@gmail.com> On Thu, Feb 29, 2024 at 11:16:20PM +0000, Puranjay Mohan wrote: > Make arch_kunwind_consume_entry() as __always_inline otherwise the > compiler might not inline it and allow attaching probes to it. > > Without this, just probing arch_kunwind_consume_entry() via > /kprobe_events will crash the kernel on arm64. > > The crash can be reproduced using the following compiler and kernel > combination: > clang version 19.0.0git (https://github.com/llvm/llvm-project.git d68d29516102252f6bf6dc23fb22cef144ca1cb3) > commit 87adedeba51a ("Merge tag 'net-6.8-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net") > > [root@localhost ~]# echo 'p arch_kunwind_consume_entry' > /sys/kernel/debug/tracing/kprobe_events > [root@localhost ~]# echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable > > Modules linked in: aes_ce_blk aes_ce_cipher ghash_ce sha2_ce virtio_net sha256_arm64 sha1_ce arm_smccc_trng net_failover failover virtio_mmio uio_pdrv_genirq uio sch_fq_codel dm_mod dax configfs > CPU: 3 PID: 1405 Comm: bash Not tainted 6.8.0-rc6+ #14 > Hardware name: linux,dummy-virt (DT) > pstate: 604003c5 (nZCv DAIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--) > pc : kprobe_breakpoint_handler+0x17c/0x258 > lr : kprobe_breakpoint_handler+0x17c/0x258 > sp : ffff800085d6ab60 > x29: ffff800085d6ab60 x28: ffff0000066f0040 x27: ffff0000066f0b20 > x26: ffff800081fa7b0c x25: 0000000000000002 x24: ffff00000b29bd18 > x23: ffff00007904c590 x22: ffff800081fa6590 x21: ffff800081fa6588 > x20: ffff00000b29bd18 x19: ffff800085d6ac40 x18: 0000000000000079 > x17: 0000000000000001 x16: ffffffffffffffff x15: 0000000000000004 > x14: ffff80008277a940 x13: 0000000000000003 x12: 0000000000000003 > x11: 00000000fffeffff x10: c0000000fffeffff x9 : aa95616fdf80cc00 > x8 : aa95616fdf80cc00 x7 : 205d343137373231 x6 : ffff800080fb48ec > x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000 > x2 : 0000000000000000 x1 : ffff800085d6a910 x0 : 0000000000000079 > Call trace: > kprobes: Failed to recover from reentered kprobes. > kprobes: Dump kprobe: > .symbol_name = arch_kunwind_consume_entry, .offset = 0, .addr = arch_kunwind_consume_entry+0x0/0x40 > ------------[ cut here ]------------ > kernel BUG at arch/arm64/kernel/probes/kprobes.c:241! > kprobes: Failed to recover from reentered kprobes. > kprobes: Dump kprobe: > .symbol_name = arch_kunwind_consume_entry, .offset = 0, .addr = arch_kunwind_consume_entry+0x0/0x40 > > Fixes: 1aba06e7b2b49 ("arm64: stacktrace: factor out kunwind_stack_walk()") > Signed-off-by: Puranjay Mohan Thanks for this! Whoops; I had meant to make this __always_inline (or noinstr), but I evidently messed that up. I don't recall any problem with making this __always_inline, and that's preferable here to allow the compiler to fold some of the indirection. >From a scan of stacktrace.c I don't see anything else that needs similar treatment; the other functions lacking __always_inline and noinstr are safe to instrument as they aren't core to the unwinder, and won't recurse into themselves in a problematic way. Given all the above: Reviewed-by: Mark Rutland Catalin, Will, are you happy to queue this as a fix? Mark. > --- > arch/arm64/kernel/stacktrace.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c > index 7f88028a00c0..b2a60e0bcfd2 100644 > --- a/arch/arm64/kernel/stacktrace.c > +++ b/arch/arm64/kernel/stacktrace.c > @@ -247,7 +247,7 @@ struct kunwind_consume_entry_data { > void *cookie; > }; > > -static bool > +static __always_inline bool > arch_kunwind_consume_entry(const struct kunwind_state *state, void *cookie) > { > struct kunwind_consume_entry_data *data = cookie; > > base-commit: 87adedeba51a822533649b143232418b9e26d08b > -- > 2.40.1 >