From patchwork Mon May 16 20:54:38 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Markus Boehme X-Patchwork-Id: 573232 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 41CADC433EF for ; Mon, 16 May 2022 21:14:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348029AbiEPVN7 (ORCPT ); Mon, 16 May 2022 17:13:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34998 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350362AbiEPVM0 (ORCPT ); Mon, 16 May 2022 17:12:26 -0400 X-Greylist: delayed 539 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Mon, 16 May 2022 14:04:08 PDT Received: from mout-p-103.mailbox.org (mout-p-103.mailbox.org [80.241.56.161]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1360D40904 for ; Mon, 16 May 2022 14:04:07 -0700 (PDT) Received: from smtp202.mailbox.org (smtp202.mailbox.org [IPv6:2001:67c:2050:b231:465::202]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-384) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-103.mailbox.org (Postfix) with ESMTPS id 4L2BN35B62z9sSh; Mon, 16 May 2022 22:55:15 +0200 (CEST) From: Markus Boehme To: stable@vger.kernel.org Cc: Miroslav Benes , Juergen Gross , Markus Boehme Subject: [PATCH 1/2] x86/xen: Make the boot CPU idle task reliable Date: Mon, 16 May 2022 22:54:38 +0200 Message-Id: <20220516205439.255114-2-markubo@amazon.com> In-Reply-To: <20220516205439.255114-1-markubo@amazon.com> References: <20220516205439.255114-1-markubo@amazon.com> MIME-Version: 1.0 X-MBO-RS-ID: 7bdcb081f16ce2e07b8 X-MBO-RS-META: t98x48y3ycm1ukc7wzmts4c9qnpmptrg X-Rspamd-Queue-Id: 4L2BN35B62z9sSh Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Miroslav Benes upstream commit 2f62f36e62daec43aa7b9633ef7f18e042a80bed The unwinder reports the boot CPU idle task's stack on XEN PV as unreliable, which affects at least live patching. There are two reasons for this. First, the task does not follow the x86 convention that its stack starts at the offset right below saved pt_regs. It allows the unwinder to easily detect the end of the stack and verify it. Second, startup_xen() function does not store the return address before jumping to xen_start_kernel() which confuses the unwinder. Amend both issues by moving the starting point of initial stack in startup_xen() and storing the return address before the jump, which is exactly what call instruction does. Signed-off-by: Miroslav Benes Reviewed-by: Juergen Gross Signed-off-by: Juergen Gross Signed-off-by: Markus Boehme --- arch/x86/xen/xen-head.S | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index c1d8b90aa4e2..deb6abe5d346 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -35,7 +35,11 @@ ENTRY(startup_xen) rep __ASM_SIZE(stos) mov %_ASM_SI, xen_start_info - mov $init_thread_union+THREAD_SIZE, %_ASM_SP +#ifdef CONFIG_X86_64 + mov initial_stack(%rip), %rsp +#else + mov pa(initial_stack), %esp +#endif #ifdef CONFIG_X86_64 /* Set up %gs. @@ -51,7 +55,7 @@ ENTRY(startup_xen) wrmsr #endif - jmp xen_start_kernel + call xen_start_kernel END(startup_xen) __FINIT #endif From patchwork Mon May 16 20:54:39 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Markus Boehme X-Patchwork-Id: 573686 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1CE7AC433FE for ; Mon, 16 May 2022 21:13:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346473AbiEPVNm (ORCPT ); Mon, 16 May 2022 17:13:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36386 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350356AbiEPVMZ (ORCPT ); Mon, 16 May 2022 17:12:25 -0400 X-Greylist: delayed 537 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Mon, 16 May 2022 14:04:08 PDT Received: from mout-p-103.mailbox.org (mout-p-103.mailbox.org [IPv6:2001:67c:2050:0:465::103]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 324A940907 for ; Mon, 16 May 2022 14:04:07 -0700 (PDT) Received: from smtp202.mailbox.org (smtp202.mailbox.org [10.196.197.202]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-384) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-103.mailbox.org (Postfix) with ESMTPS id 4L2BN46f6pz9sTG; Mon, 16 May 2022 22:55:16 +0200 (CEST) From: Markus Boehme To: stable@vger.kernel.org Cc: Miroslav Benes , Juergen Gross , Markus Boehme Subject: [PATCH 2/2] x86/xen: Make the secondary CPU idle tasks reliable Date: Mon, 16 May 2022 22:54:39 +0200 Message-Id: <20220516205439.255114-3-markubo@amazon.com> In-Reply-To: <20220516205439.255114-1-markubo@amazon.com> References: <20220516205439.255114-1-markubo@amazon.com> MIME-Version: 1.0 X-MBO-RS-ID: 23f38b479fca7b33fcd X-MBO-RS-META: nf5zz7s37ag36mczewkj1fsq5kjx9s8k Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Miroslav Benes upstream commit c3881eb58d56116c79ac4ee4f40fd15ead124c4b The unwinder reports the secondary CPU idle tasks' stack on XEN PV as unreliable, which affects at least live patching. cpu_initialize_context() sets up the context of the CPU through VCPUOP_initialise hypercall. After it is woken up, the idle task starts in cpu_bringup_and_idle() function and its stack starts at the offset right below pt_regs. The unwinder correctly detects the end of stack there but it is confused by NULL return address in the last frame. Introduce a wrapper in assembly, which just calls cpu_bringup_and_idle(). The return address is thus pushed on the stack and the wrapper contains the annotation hint for the unwinder regarding the stack state. Signed-off-by: Miroslav Benes Reviewed-by: Juergen Gross Signed-off-by: Juergen Gross Signed-off-by: Markus Boehme --- arch/x86/xen/smp_pv.c | 3 ++- arch/x86/xen/xen-head.S | 10 ++++++++++ 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c index 64e6ec2c32a7..9d9777ded5f7 100644 --- a/arch/x86/xen/smp_pv.c +++ b/arch/x86/xen/smp_pv.c @@ -53,6 +53,7 @@ static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 }; static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 }; static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id); +void asm_cpu_bringup_and_idle(void); static void cpu_bringup(void) { @@ -310,7 +311,7 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle) * pointing just below where pt_regs would be if it were a normal * kernel entry. */ - ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle; + ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle; ctxt->flags = VGCF_IN_KERNEL; ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */ ctxt->user_regs.ds = __USER_DS; diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index deb6abe5d346..591544b4b85a 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -58,6 +58,16 @@ ENTRY(startup_xen) call xen_start_kernel END(startup_xen) __FINIT + +#ifdef CONFIG_XEN_PV_SMP +.pushsection .text +SYM_CODE_START(asm_cpu_bringup_and_idle) + UNWIND_HINT_EMPTY + + call cpu_bringup_and_idle +SYM_CODE_END(asm_cpu_bringup_and_idle) +.popsection +#endif #endif .pushsection .text