Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit ee6214ce authored by Sandeepa Prabhu's avatar Sandeepa Prabhu Committed by Catalin Marinas
Browse files

arm64: support single-step and breakpoint handler hooks 



AArch64 Single Steping and Breakpoint debug exceptions will be
used by multiple debug framworks like kprobes & kgdb.

This patch implements the hooks for those frameworks to register
their own handlers for handling breakpoint and single step events.

Reworked the debug exception handler in entry.S: do_dbg to route
software breakpoint (BRK64) exception to do_debug_exception()

Signed-off-by: default avatarSandeepa Prabhu <sandeepa.prabhu@linaro.org>
Signed-off-by: default avatarDeepak Saxena <dsaxena@linaro.org>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 26920dd2

arch/arm64/include/asm/debug-monitors.h

+21 −0
Original line number Original line Diff line number Diff line
@@ -62,6 +62,27 @@ struct task_struct; 




#define DBG_ARCH_ID_RESERVED	0	/* In case of ptrace ABI updates. */

#define DBG_ARCH_ID_RESERVED	0	/* In case of ptrace ABI updates. */





#define DBG_HOOK_HANDLED	0

#define DBG_HOOK_ERROR		1



struct step_hook {

	struct list_head node;

	int (*fn)(struct pt_regs *regs, unsigned int esr);

};



void register_step_hook(struct step_hook *hook);

void unregister_step_hook(struct step_hook *hook);



struct break_hook {

	struct list_head node;

	u32 esr_val;

	u32 esr_mask;

	int (*fn)(struct pt_regs *regs, unsigned int esr);

};



void register_break_hook(struct break_hook *hook);

void unregister_break_hook(struct break_hook *hook);



u8 debug_monitors_arch(void);

u8 debug_monitors_arch(void);





void enable_debug_monitors(enum debug_el el);

void enable_debug_monitors(enum debug_el el);

arch/arm64/kernel/debug-monitors.c

+87 −1
Original line number Original line Diff line number Diff line
@@ -187,6 +187,48 @@ static void clear_regs_spsr_ss(struct pt_regs *regs) 
	regs->pstate = spsr;

	regs->pstate = spsr;

}

}





/* EL1 Single Step Handler hooks */

static LIST_HEAD(step_hook);

DEFINE_RWLOCK(step_hook_lock);



void register_step_hook(struct step_hook *hook)

{

	write_lock(&step_hook_lock);

	list_add(&hook->node, &step_hook);

	write_unlock(&step_hook_lock);

}



void unregister_step_hook(struct step_hook *hook)

{

	write_lock(&step_hook_lock);

	list_del(&hook->node);

	write_unlock(&step_hook_lock);

}



/*

 * Call registered single step handers

 * There is no Syndrome info to check for determining the handler.

 * So we call all the registered handlers, until the right handler is

 * found which returns zero.

 */

static int call_step_hook(struct pt_regs *regs, unsigned int esr)

{

	struct step_hook *hook;

	int retval = DBG_HOOK_ERROR;



	read_lock(&step_hook_lock);



	list_for_each_entry(hook, &step_hook, node)	{

		retval = hook->fn(regs, esr);

		if (retval == DBG_HOOK_HANDLED)

			break;

	}



	read_unlock(&step_hook_lock);



	return retval;

}



static int single_step_handler(unsigned long addr, unsigned int esr,

static int single_step_handler(unsigned long addr, unsigned int esr,

			       struct pt_regs *regs)

			       struct pt_regs *regs)

{

{
@@ -214,7 +256,9 @@ static int single_step_handler(unsigned long addr, unsigned int esr, 
		 */

		 */

		user_rewind_single_step(current);

		user_rewind_single_step(current);

	} else {

	} else {

		/* TODO: route to KGDB */

		if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED)

			return 0;



		pr_warning("Unexpected kernel single-step exception at EL1\n");

		pr_warning("Unexpected kernel single-step exception at EL1\n");

		/*

		/*

		 * Re-enable stepping since we know that we will be

		 * Re-enable stepping since we know that we will be
@@ -226,11 +270,53 @@ static int single_step_handler(unsigned long addr, unsigned int esr, 
	return 0;

	return 0;

}

}





/*

 * Breakpoint handler is re-entrant as another breakpoint can

 * hit within breakpoint handler, especically in kprobes.

 * Use reader/writer locks instead of plain spinlock.

 */

static LIST_HEAD(break_hook);

DEFINE_RWLOCK(break_hook_lock);



void register_break_hook(struct break_hook *hook)

{

	write_lock(&break_hook_lock);

	list_add(&hook->node, &break_hook);

	write_unlock(&break_hook_lock);

}



void unregister_break_hook(struct break_hook *hook)

{

	write_lock(&break_hook_lock);

	list_del(&hook->node);

	write_unlock(&break_hook_lock);

}



static int call_break_hook(struct pt_regs *regs, unsigned int esr)

{

	struct break_hook *hook;

	int (*fn)(struct pt_regs *regs, unsigned int esr) = NULL;



	read_lock(&break_hook_lock);

	list_for_each_entry(hook, &break_hook, node)

		if ((esr & hook->esr_mask) == hook->esr_val)

			fn = hook->fn;

	read_unlock(&break_hook_lock);



	return fn ? fn(regs, esr) : DBG_HOOK_ERROR;

}



static int brk_handler(unsigned long addr, unsigned int esr,

static int brk_handler(unsigned long addr, unsigned int esr,

		       struct pt_regs *regs)

		       struct pt_regs *regs)

{

{

	siginfo_t info;

	siginfo_t info;





	if (call_break_hook(regs, esr) == DBG_HOOK_HANDLED)

		return 0;



	pr_warn("unexpected brk exception at %lx, esr=0x%x\n",

			(long)instruction_pointer(regs), esr);



	if (!user_mode(regs))

	if (!user_mode(regs))

		return -EFAULT;

		return -EFAULT;

arch/arm64/kernel/entry.S

+2 −0
Original line number Original line Diff line number Diff line
@@ -288,6 +288,8 @@ el1_dbg: 
	/*

	/*

	 * Debug exception handling

	 * Debug exception handling

	 */

	 */

	cmp	x24, #ESR_EL1_EC_BRK64		// if BRK64

	cinc	x24, x24, eq			// set bit '0'

	tbz	x24, #0, el1_inv		// EL1 only

	tbz	x24, #0, el1_inv		// EL1 only

	mrs	x0, far_el1

	mrs	x0, far_el1

	mov	x2, sp				// struct pt_regs

	mov	x2, sp				// struct pt_regs