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Commit 9ebb3cbc authored by Will Deacon's avatar Will Deacon
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ARM: hw_breakpoint: unify single-stepping code for watchpoints and breakpoints 



The single-stepping code is currently different depending on whether
we are stepping over a breakpoint or a watchpoint. There is no good
reason for this, so let's sort it out.

This patch adds functions for enabling/disabling single-step for
a particular hw_breakpoint and integrates this with the exception
handling code.

Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 93a04a34

arch/arm/kernel/hw_breakpoint.c

+40 −41
Original line number Diff line number Diff line
@@ -339,6 +339,11 @@ int arch_install_hw_breakpoint(struct perf_event *bp) 
		val_base = ARM_BASE_BVR;

		slots = __get_cpu_var(bp_on_reg);

		max_slots = core_num_brps;

		if (info->step_ctrl.enabled) {

			/* Override the breakpoint data with the step data. */

			addr = info->trigger & ~0x3;

			ctrl = encode_ctrl_reg(info->step_ctrl);

		}

	} else {

		/* Watchpoint */

		if (info->step_ctrl.enabled) {
@@ -628,21 +633,28 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp) 
	return ret;

}



static void update_mismatch_flag(int idx, int flag)

/*

 * Enable/disable single-stepping over the breakpoint bp at address addr.

 */

static void enable_single_step(struct perf_event *bp, u32 addr)

{

	struct perf_event *bp = __get_cpu_var(bp_on_reg[idx]);

	struct arch_hw_breakpoint *info;



	if (bp == NULL)

		return;



	info = counter_arch_bp(bp);

	struct arch_hw_breakpoint *info = counter_arch_bp(bp);



	/* Update the mismatch field to enter/exit `single-step' mode */

	if (!bp->overflow_handler && info->ctrl.mismatch != flag) {

		info->ctrl.mismatch = flag;

		write_wb_reg(ARM_BASE_BCR + idx, encode_ctrl_reg(info->ctrl) | 0x1);

	arch_uninstall_hw_breakpoint(bp);

	info->step_ctrl.mismatch  = 1;

	info->step_ctrl.len	  = ARM_BREAKPOINT_LEN_4;

	info->step_ctrl.type	  = ARM_BREAKPOINT_EXECUTE;

	info->step_ctrl.privilege = info->ctrl.privilege;

	info->step_ctrl.enabled	  = 1;

	info->trigger		  = addr;

	arch_install_hw_breakpoint(bp);

}



static void disable_single_step(struct perf_event *bp)

{

	arch_uninstall_hw_breakpoint(bp);

	counter_arch_bp(bp)->step_ctrl.enabled = 0;

	arch_install_hw_breakpoint(bp);

}



static void watchpoint_handler(unsigned long unknown, struct pt_regs *regs)
@@ -679,16 +691,8 @@ static void watchpoint_handler(unsigned long unknown, struct pt_regs *regs) 
		 * mismatch breakpoint so we can single-step over the

		 * watchpoint trigger.

		 */

		if (!wp->overflow_handler) {

			arch_uninstall_hw_breakpoint(wp);

			info->step_ctrl.mismatch  = 1;

			info->step_ctrl.len	  = ARM_BREAKPOINT_LEN_4;

			info->step_ctrl.type	  = ARM_BREAKPOINT_EXECUTE;

			info->step_ctrl.privilege = info->ctrl.privilege;

			info->step_ctrl.enabled	  = 1;

			info->trigger		  = regs->ARM_pc;

			arch_install_hw_breakpoint(wp);

		}

		if (!wp->overflow_handler)

			enable_single_step(wp, instruction_pointer(regs));



		rcu_read_unlock();

	}
@@ -716,11 +720,8 @@ static void watchpoint_single_step_handler(unsigned long pc) 
		 * Restore the original watchpoint if we've completed the

		 * single-step.

		 */

		if (info->trigger != pc) {

			arch_uninstall_hw_breakpoint(wp);

			info->step_ctrl.enabled = 0;

			arch_install_hw_breakpoint(wp);

		}

		if (info->trigger != pc)

			disable_single_step(wp);



unlock:

		rcu_read_unlock();
@@ -730,7 +731,6 @@ static void watchpoint_single_step_handler(unsigned long pc) 
static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs)

{

	int i;

	int mismatch;

	u32 ctrl_reg, val, addr;

	struct perf_event *bp, **slots = __get_cpu_var(bp_on_reg);

	struct arch_hw_breakpoint *info;
@@ -745,34 +745,33 @@ static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs) 


		bp = slots[i];



		if (bp == NULL) {

			rcu_read_unlock();

			continue;

		}

		if (bp == NULL)

			goto unlock;



		mismatch = 0;

		info = counter_arch_bp(bp);



		/* Check if the breakpoint value matches. */

		val = read_wb_reg(ARM_BASE_BVR + i);

		if (val != (addr & ~0x3))

			goto unlock;

			goto mismatch;



		/* Possible match, check the byte address select to confirm. */

		ctrl_reg = read_wb_reg(ARM_BASE_BCR + i);

		decode_ctrl_reg(ctrl_reg, &ctrl);

		if ((1 << (addr & 0x3)) & ctrl.len) {

			mismatch = 1;

			info = counter_arch_bp(bp);

			info->trigger = addr;

		}



unlock:

		if (mismatch && !info->ctrl.mismatch) {

			pr_debug("breakpoint fired: address = 0x%x\n", addr);

			perf_bp_event(bp, regs);

			if (!bp->overflow_handler)

				enable_single_step(bp, addr);

			goto unlock;

		}



		update_mismatch_flag(i, mismatch);

mismatch:

		/* If we're stepping a breakpoint, it can now be restored. */

		if (info->step_ctrl.enabled)

			disable_single_step(bp);

unlock:

		rcu_read_unlock();

	}

arch/arm/include/asm/hw_breakpoint.h

+2 −2

File changed.

Contains only whitespace changes.