From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751318AbeEBUuP (ORCPT ); Wed, 2 May 2018 16:50:15 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:54104 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750939AbeEBUuK (ORCPT ); Wed, 2 May 2018 16:50:10 -0400 Date: Wed, 2 May 2018 15:50:09 -0500 From: Josh Poimboeuf To: Vince Weaver Cc: Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org, Arnaldo Carvalho de Melo , Thomas Gleixner , Andy Lutomirski Subject: Re: perf: fuzzer causes stack going in wrong direction warnings Message-ID: <20180502205009.codkvscnh4j4hm6b@treble> References: <20180109160551.GK3040@hirez.programming.kicks-ass.net> <20180109170716.bqmexpmywwr4bwuv@treble> <20180111052538.2qhj6oxnc24xumhk@treble> <20180111192112.d35nkotzklicd27c@treble> <20180501135850.enx4waqd5d7yowlj@treble> <20180501220458.p3rgwzh3jcqt4jmm@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180501220458.p3rgwzh3jcqt4jmm@treble> User-Agent: Mutt/1.6.0.1 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 01, 2018 at 05:04:58PM -0500, Josh Poimboeuf wrote: > On Tue, May 01, 2018 at 03:59:31PM -0400, Vince Weaver wrote: > > On Tue, 1 May 2018, Josh Poimboeuf wrote: > > > > > Can you try the following patch? > > > > I applied the patch, but the warnings don't really look that different. > > > > [ 62.220322] WARNING: stack recursion on stack type 4 > > [ 62.220326] WARNING: can't dereference registers at 000000009ca2e86d for ip swapgs_restore_regs_and_return_to_usermode+0x79/0x87 > > [ 367.597013] WARNING: stack going in the wrong direction? ip=native_sched_clock+0x9/0x90 > > Bummer. I'll need to come up with a patch to dump more info. After looking closer, I realized that at least some of these warnings are due to bad unwind hints in the entry code. Can you try this patch instead of the last one? diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index be63330c5511..73f5d4c10304 100644 --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -165,6 +165,7 @@ For 32-bit we have the following conventions - kernel is built with .endif popq %rdx popq %rsi + UNWIND_HINT_IRET_REGS offset=16 .if \pop_rdi popq %rdi .endif diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 805f52703ee3..c6c54ce30090 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -306,7 +306,6 @@ GLOBAL(entry_SYSCALL_64_after_hwframe) */ syscall_return_via_sysret: /* rcx and r11 are already restored (see code above) */ - UNWIND_HINT_EMPTY POP_REGS pop_rdi=0 skip_r11rcx=1 /* @@ -315,6 +314,7 @@ syscall_return_via_sysret: */ movq %rsp, %rdi movq PER_CPU_VAR(cpu_tss_rw + TSS_sp0), %rsp + UNWIND_HINT_EMPTY pushq RSP-RDI(%rdi) /* RSP */ pushq (%rdi) /* RDI */ @@ -666,6 +666,7 @@ GLOBAL(swapgs_restore_regs_and_return_to_usermode) */ movq %rsp, %rdi movq PER_CPU_VAR(cpu_tss_rw + TSS_sp0), %rsp + UNWIND_HINT_EMPTY /* Copy the IRET frame to the trampoline stack. */ pushq 6*8(%rdi) /* SS */ @@ -1640,6 +1641,7 @@ nmi_restore: * at the "iret" frame. */ addq $6*8, %rsp + UNWIND_HINT_IRET_REGS /* * Clear "NMI executing". Set DF first so that we can easily diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 92b6a2c21631..d66f14bb6c50 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1239,7 +1239,7 @@ static int update_insn_state_regs(struct instruction *insn, struct insn_state *s struct cfi_reg *cfa = &state->cfa; struct stack_op *op = &insn->stack_op; - if (cfa->base != CFI_SP) + if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT) return 0; /* push */