x86/traps: Restructure #DB handling (9347f413) · Commits · 戴 / test

arch/x86/kernel/traps.c

+35 −34

Original line number	Diff line number	Diff line
		@@ -775,39 +775,12 @@ static __always_inline void debug_exit(unsigned long dr7)
		*
		* May run on IST stack.
		*/
		static noinstr void handle_debug(struct pt_regs *regs, unsigned long dr6)
		static void noinstr handle_debug(struct pt_regs *regs, unsigned long dr6,
		bool user_icebp)
		{
		struct task_struct *tsk = current;
		int user_icebp = 0;
		int si_code;

		/*
		* The SDM says "The processor clears the BTF flag when it
		* generates a debug exception." Clear TIF_BLOCKSTEP to keep
		* TIF_BLOCKSTEP in sync with the hardware BTF flag.
		*/
		clear_tsk_thread_flag(tsk, TIF_BLOCKSTEP);

		if (unlikely(!user_mode(regs) && (dr6 & DR_STEP) &&
		is_sysenter_singlestep(regs))) {
		dr6 &= ~DR_STEP;
		if (!dr6)
		return;
		/*
		* else we might have gotten a single-step trap and hit a
		* watchpoint at the same time, in which case we should fall
		* through and handle the watchpoint.
		*/
		}

		/*
		* If dr6 has no reason to give us about the origin of this trap,
		* then it's very likely the result of an icebp/int01 trap.
		* User wants a sigtrap for that.
		*/
		if (!dr6 && user_mode(regs))
		user_icebp = 1;

		/* Store the virtualized DR6 value */
		tsk->thread.debugreg6 = dr6;

		@@ -832,9 +805,7 @@ static noinstr void handle_debug(struct pt_regs *regs, unsigned long dr6)
		if (v8086_mode(regs)) {
		handle_vm86_trap((struct kernel_vm86_regs *) regs, 0,
		X86_TRAP_DB);
		cond_local_irq_disable(regs);
		debug_stack_usage_dec();
		return;
		goto out;
		}

		if (WARN_ON_ONCE((dr6 & DR_STEP) && !user_mode(regs))) {
		@@ -848,9 +819,12 @@ static noinstr void handle_debug(struct pt_regs *regs, unsigned long dr6)
		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) \|\| user_icebp)
		send_sigtrap(regs, 0, si_code);

		out:
		cond_local_irq_disable(regs);
		debug_stack_usage_dec();
		}
		@@ -859,7 +833,27 @@ static __always_inline void exc_debug_kernel(struct pt_regs *regs,
		unsigned long dr6)
		{
		nmi_enter();
		handle_debug(regs, dr6);
		/*
		* The SDM says "The processor clears the BTF flag when it
		* generates a debug exception." Clear TIF_BLOCKSTEP to keep
		* TIF_BLOCKSTEP in sync with the hardware BTF flag.
		*/
		clear_thread_flag(TIF_BLOCKSTEP);

		/*
		* Catch SYSENTER with TF set and clear DR_STEP. If this hit a
		* watchpoint at the same time then that will still be handled.
		*/
		if ((dr6 & DR_STEP) && is_sysenter_singlestep(regs))
		dr6 &= ~DR_STEP;

		/*
		* If DR6 is zero, no point in trying to handle it. The kernel is
		* not using INT1.
		*/
		if (dr6)
		handle_debug(regs, dr6, false);

		nmi_exit();
		}

		@@ -867,7 +861,14 @@ static __always_inline void exc_debug_user(struct pt_regs *regs,
		unsigned long dr6)
		{
		idtentry_enter(regs);
		handle_debug(regs, dr6);
		clear_thread_flag(TIF_BLOCKSTEP);

		/*
		* If dr6 has no reason to give us about the origin of this trap,
		* then it's very likely the result of an icebp/int01 trap.
		* User wants a sigtrap for that.
		*/
		handle_debug(regs, dr6, !dr6);
		idtentry_exit(regs);
		}

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