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Commit 08d68323 authored by K.Prasad's avatar K.Prasad Committed by Frederic Weisbecker
Browse files

hw-breakpoints: modifying generic debug exception to use thread-specific debug registers 



This patch modifies the breakpoint exception handler code to use the new
abstract debug register names.

[ fweisbec@gmail.com: fix conflict against kmemcheck ]

[ Impact: refactor and cleanup x86 debug exception handler ]

Original-patch-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarK.Prasad <prasad@linux.vnet.ibm.com>
Reviewed-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
parent 0067f129

arch/x86/kernel/traps.c

+24 −45
Original line number Diff line number Diff line
@@ -529,73 +529,52 @@ asmlinkage __kprobes struct pt_regs *sync_regs(struct pt_regs *eregs) 
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);



	/* 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;

	if (regs->flags & X86_VM_MASK) {

		handle_vm86_trap((struct kernel_vm86_regs *) regs,

				error_code, 1);

		return;

	}



#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).

	 * 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.

	 */

	if (condition & DR_STEP) {

		if (!user_mode(regs))

			goto clear_TF_reenable;

	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(condition);

	/* Ok, finally something we can handle */

	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);



	/*

	 * Disable additional traps. They'll be re-enabled when

	 * the signal is delivered.

	 */

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;

	preempt_conditional_cli(regs);

	return;

}