From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 625E2189B94 for ; Tue, 30 Jul 2024 19:22:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722367374; cv=none; b=REcTCRVrS0jCY/xsO1mCfwWlvWhlIzcUUBsChN8uVScNDpEJvv9L97+4lyH9WldCYzL/JFQNXeNltWUfm+votzPlCFGZUJJEnE4NgTe6zlsFiXnZIbngQ7/DjMbU8tdG2Pd5IsgqoRnii13E3QgbpYPibTB6horQvf+vKDAyJoE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722367374; c=relaxed/simple; bh=exU5Yc8xgZaMWWaT3tSQFyGZhYBy0BCDsIGDgbVngZk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=h3JTeLylYNCC9NGfQIdZC+8+lIZNs2EKDFJH15qQMXy2h2GrOZK/+FNqssJREWTS/qPvW2AeXT+URfEbxPp7E8iCnsLcNRCBRE4D8VVyBkeQUtBXZEc4iJQ5EnaZ/K7MK5ljsUyjMIOosTYlyCKx+9WsJzgIRyoqibfBIB4uOp4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=FroozuDP; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="FroozuDP" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=BbRYxi6Z1xQuUKuePlP3pOg74/6zRtxxA0g/pAZgPD4=; b=FroozuDPORgBvo1zWZ9A6Pp6fU 6Rusqt0OEzX3jmvVUToMJziYiLHaihuI91wMclzgEeQWWlXLwfnzD2XfM/rUjZkleLlHr1BLPQI0d 3IMrZRWXpNpqj/3RLxUUu3q5N/8stz2QMtCdVt+SBTGmeh8GvTomJJ5sm/ffT4EkuCP7FcnipDZoM nDfigsvFvTNlPu8RlKA+t5YVRiMOMopgGZxtnMTtaCbCGZLz7EXUVn/dt/6+Ac/k2YUuKLoq/nt+U EDOVC3Bpllu85BtwgzXOvcD+BwvLf9bICE45gwIZX9KV2ce3LYAm3pPfJA45thu3LCnhvB5+2/ewo B3YVkeAQ==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.97.1 #2 (Red Hat Linux)) id 1sYsQg-000000054fN-2Jy9; Tue, 30 Jul 2024 19:22:43 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 5121E3003EA; Tue, 30 Jul 2024 21:22:37 +0200 (CEST) Date: Tue, 30 Jul 2024 21:22:37 +0200 From: Peter Zijlstra To: Linus Torvalds Cc: Guenter Roeck , Andy Lutomirski , Ingo Molnar , Peter Anvin , Linux Kernel Mailing List , Jens Axboe , the arch/x86 maintainers Subject: Re: Linux 6.11-rc1 Message-ID: <20240730192237.GR33588@noisy.programming.kicks-ass.net> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Jul 30, 2024 at 11:53:31AM -0700, Linus Torvalds wrote: > Which makes me think it's asm_exc_int3 just recursively failing. Sounds like text_poke() going sideways, there's a jump_label fail out there: https://lkml.kernel.org/r/20240730132626.GV26599@noisy.programming.kicks-ass.net > Let's see it x86 people have some idea, but that > > restore_all_switch_stack+0x65/0xe6 > > and doing an objdump to see the code generation, it is literally here: > > 0f 20 d8 mov %cr3,%eax > 0d 00 10 00 00 or $0x1000,%eax > 0f 22 d8 mov %eax,%cr3 That looks like SWITCH_TO_USER_CR3 > eb 16 jmp > > with that "jmp" instruction being the restore_all_switch_stack+0x65 address. Thish would make this BUG_IF_WRONG_CR3, which starts with an ALTERNATIVE jmp. I think we landed a pile of ALTERNATIVE patches this merge window. That said, Boris did spend an awful lot of time testing them... but this is 32bit so who knows how much time that got.