Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755884AbZFASOa (ORCPT ); Mon, 1 Jun 2009 14:14:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754259AbZFASOO (ORCPT ); Mon, 1 Jun 2009 14:14:14 -0400 Received: from e28smtp03.in.ibm.com ([59.145.155.3]:37978 "EHLO e28smtp03.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754995AbZFASOM (ORCPT ); Mon, 1 Jun 2009 14:14:12 -0400 Date: Mon, 1 Jun 2009 23:44:08 +0530 From: "K.Prasad" To: Frederic Weisbecker Cc: Linux Kernel Mailing List , Ingo Molnar , Alan Stern , "K.Prasad" Subject: [Patch 04/12] Modifying generic debug exception to use thread-specific debug registers Message-ID: <20090601181408.GE23582@in.ibm.com> References: <20090601180605.799735829@prasadkr_t60p.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline; filename=modify_debug_exception_handler_04 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3881 Lines: 124 This patch modifies the breakpoint exception handler code to use the abstract register names. Original-patch-by: Alan Stern Signed-off-by: K.Prasad Reviewed-by: Alan Stern --- arch/x86/kernel/traps.c | 76 +++++++++++++++++------------------------------- 1 file changed, 27 insertions(+), 49 deletions(-) Index: linux-2.6-tip.hbkpt/arch/x86/kernel/traps.c =================================================================== --- linux-2.6-tip.hbkpt.orig/arch/x86/kernel/traps.c +++ linux-2.6-tip.hbkpt/arch/x86/kernel/traps.c @@ -530,76 +530,54 @@ asmlinkage __kprobes struct pt_regs *syn dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code) { struct task_struct *tsk = current; - unsigned long condition; + unsigned long dr6; int si_code; - get_debugreg(condition, 6); + get_debugreg(dr6, 6); /* Catch kmemcheck conditions first of all! */ - if (condition & DR_STEP && kmemcheck_trap(regs)) + if (((dr6 & DR_STEP) && kmemcheck_trap(regs)) && + !(dr6 & DR_TRAP_BITS)) return; - + /* DR6 may or may not be cleared by the CPU */ + set_debugreg(0, 6); /* * The processor cleared BTF, so don't mark that we need it set. */ clear_tsk_thread_flag(tsk, TIF_DEBUGCTLMSR); tsk->thread.debugctlmsr = 0; - if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code, + /* Store the virtualized DR6 value */ + tsk->thread.debugreg6 = dr6; + + if (notify_die(DIE_DEBUG, "debug", regs, dr6, error_code, SIGTRAP) == NOTIFY_STOP) return; /* It's safe to allow irq's after DR6 has been saved */ preempt_conditional_sti(regs); - /* Mask out spurious debug traps due to lazy DR7 setting */ - if (condition & (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3)) { - if (!tsk->thread.debugreg7) - goto clear_dr7; - } - -#ifdef CONFIG_X86_32 - if (regs->flags & X86_VM_MASK) - goto debug_vm86; -#endif - - /* Save debug status register where ptrace can see it */ - tsk->thread.debugreg6 = condition; - - /* - * Single-stepping through TF: make sure we ignore any events in - * kernel space (but re-enable TF when returning to user mode). - */ - if (condition & DR_STEP) { - if (!user_mode(regs)) - goto clear_TF_reenable; + if (regs->flags & X86_VM_MASK) { + handle_vm86_trap((struct kernel_vm86_regs *) regs, + error_code, 1); + return; } - si_code = get_si_code(condition); - /* Ok, finally something we can handle */ - send_sigtrap(tsk, regs, error_code, si_code); - /* - * Disable additional traps. They'll be re-enabled when - * the signal is delivered. + * Single-stepping through system calls: ignore any exceptions in + * kernel space, but re-enable TF when returning to user mode. + * + * We already checked v86 mode above, so we can check for kernel mode + * by just checking the CPL of CS. */ -clear_dr7: - set_debugreg(0, 7); - preempt_conditional_cli(regs); - return; - -#ifdef CONFIG_X86_32 -debug_vm86: - /* reenable preemption: handle_vm86_trap() might sleep */ - dec_preempt_count(); - handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code, 1); - conditional_cli(regs); - return; -#endif - -clear_TF_reenable: - set_tsk_thread_flag(tsk, TIF_SINGLESTEP); - regs->flags &= ~X86_EFLAGS_TF; + if ((dr6 & DR_STEP) && !user_mode(regs)) { + tsk->thread.debugreg6 &= ~DR_STEP; + set_tsk_thread_flag(tsk, TIF_SINGLESTEP); + regs->flags &= ~X86_EFLAGS_TF; + } + si_code = get_si_code(tsk->thread.debugreg6); + if (tsk->thread.debugreg6 & (DR_STEP | DR_TRAP_BITS)) + send_sigtrap(tsk, regs, error_code, si_code); preempt_conditional_cli(regs); return; } -- 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/