Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753205AbbBZD6e (ORCPT ); Wed, 25 Feb 2015 22:58:34 -0500 Received: from szxga02-in.huawei.com ([119.145.14.65]:8491 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752401AbbBZD6c (ORCPT ); Wed, 25 Feb 2015 22:58:32 -0500 From: Wang Nan To: , , , , , , , , CC: , Subject: [PATCH] x86, traps: Enable DEBUG_STACK after cpu_init() for TRAP_DB/BP. Date: Thu, 26 Feb 2015 11:57:56 +0800 Message-ID: <1424923076-6106-1-git-send-email-wangnan0@huawei.com> X-Mailer: git-send-email 1.8.4 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.107.197.247] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2458 Lines: 66 Before this patch early_trap_init() installs DEBUG_STACK for X86_TRAP_BP and X86_TRAP_DB. However, DEBUG_STACK doesn't work correctly until cpu_init() <-- trap_init(). This patch passes 0 to set_intr_gate_ist() and set_system_intr_gate_ist() instead of DEBUG_STACK to let it use same stack as kernel, and installs DEBUG_STACK for them in trap_init(). As core runs at ring 0 between early_trap_init() and trap_init(), there is no chance to get a bad stack before trap_init(). As NMI is also enabled in trap_init(), we don't need to care about is_debug_stack() and related things used in arch/x86/kernel/nmi.c. Signed-off-by: Wang Nan --- arch/x86/kernel/traps.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 9d2073e..a9b8640 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -925,9 +925,16 @@ dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code) /* Set of traps needed for early debugging. */ void __init early_trap_init(void) { - set_intr_gate_ist(X86_TRAP_DB, &debug, DEBUG_STACK); + /* + * Don't set ist to DEBUG_STACK as it doesn't work until TSS is + * ready in cpu_init() <-- trap_init(). Before trap_init(), CPU + * runs at ring 0 so there should be impossible to hit a invalid + * stack. Use original stack is enough. DEBUG_STACK will be + * equipped after cpu_init() in trap_init(). + */ + set_intr_gate_ist(X86_TRAP_DB, &debug, 0); /* int3 can be called from all */ - set_system_intr_gate_ist(X86_TRAP_BP, &int3, DEBUG_STACK); + set_system_intr_gate_ist(X86_TRAP_BP, &int3, 0); #ifdef CONFIG_X86_32 set_intr_gate(X86_TRAP_PF, page_fault); #endif @@ -1005,6 +1012,15 @@ void __init trap_init(void) */ cpu_init(); + /* + * X86_TRAP_DB and X86_TRAP_BP have been setup + * in early_trap_init(). However, DEBUG_STACK works only after + * cpu_init() load TSS. See comments in early_trap_init(). + */ + set_intr_gate_ist(X86_TRAP_DB, &debug, DEBUG_STACK); + /* int3 can be called from all */ + set_system_intr_gate_ist(X86_TRAP_BP, &int3, DEBUG_STACK); + x86_init.irqs.trap_init(); #ifdef CONFIG_X86_64 -- 1.8.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/