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Commit 1b08e907 authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

uprobes: Kill UTASK_BP_HIT state 



Kill UTASK_BP_HIT state, it buys nothing but complicates the code.
It is only used in uprobe_notify_resume() to decide who should be
called, we can check utask->active_uprobe != NULL instead. And this
allows us to simplify handle_swbp(), no need to clear utask->state.

Likewise we could kill UTASK_SSTEP, but UTASK_BP_HIT is worse and
imho should die. The problem is, it creates the special case when
task->utask is NULL, we can't distinguish RUNNING and BP_HIT. With
this patch utask == NULL always means RUNNING.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
parent 0578a970

include/linux/uprobes.h

+0 −1
Original line number Diff line number Diff line
@@ -59,7 +59,6 @@ struct uprobe_consumer { 
#ifdef CONFIG_UPROBES

enum uprobe_task_state {

	UTASK_RUNNING,

	UTASK_BP_HIT,

	UTASK_SSTEP,

	UTASK_SSTEP_ACK,

	UTASK_SSTEP_TRAPPED,

kernel/events/uprobes.c

+9 −20
Original line number Diff line number Diff line
@@ -1469,10 +1469,6 @@ static void handle_swbp(struct pt_regs *regs) 
	bp_vaddr = uprobe_get_swbp_addr(regs);

	uprobe = find_active_uprobe(bp_vaddr, &is_swbp);



	utask = current->utask;

	if (utask)

		utask->state = UTASK_RUNNING;



	if (!uprobe) {

		if (is_swbp > 0) {

			/* No matching uprobe; signal SIGTRAP. */
@@ -1491,6 +1487,7 @@ static void handle_swbp(struct pt_regs *regs) 
		return;

	}



	utask = current->utask;

	if (!utask) {

		utask = add_utask();

		/* Cannot allocate; re-execute the instruction. */
@@ -1547,13 +1544,12 @@ static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs) 
}



/*

 * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag.  (and on

 * subsequent probe hits on the thread sets the state to UTASK_BP_HIT) and

 * allows the thread to return from interrupt.

 * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag and

 * allows the thread to return from interrupt. After that handle_swbp()

 * sets utask->active_uprobe.

 *

 * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag and

 * also sets the state to UTASK_SSTEP_ACK and allows the thread to return from

 * interrupt.

 * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag

 * and allows the thread to return from interrupt.

 *

 * While returning to userspace, thread notices the TIF_UPROBE flag and calls

 * uprobe_notify_resume().
@@ -1563,10 +1559,10 @@ void uprobe_notify_resume(struct pt_regs *regs) 
	struct uprobe_task *utask;



	utask = current->utask;

	if (!utask || utask->state == UTASK_BP_HIT)

		handle_swbp(regs);

	else

	if (utask && utask->active_uprobe)

		handle_singlestep(utask, regs);

	else

		handle_swbp(regs);

}



/*
@@ -1575,17 +1571,10 @@ void uprobe_notify_resume(struct pt_regs *regs) 
 */

int uprobe_pre_sstep_notifier(struct pt_regs *regs)

{

	struct uprobe_task *utask;



	if (!current->mm || !test_bit(MMF_HAS_UPROBES, &current->mm->flags))

		return 0;



	utask = current->utask;

	if (utask)

		utask->state = UTASK_BP_HIT;



	set_thread_flag(TIF_UPROBE);



	return 1;

}