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Commit e78aebfd authored by Anton Arapov's avatar Anton Arapov Committed by Oleg Nesterov
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uretprobes: Reserve the first slot in xol_vma for trampoline 



Allocate trampoline page, as the very first one in uprobed
task xol area, and fill it with breakpoint opcode.

Also introduce get_trampoline_vaddr() helper, to wrap the
trampoline address extraction from area->vaddr. That removes
confusion and eases the debug experience in case ->vaddr
notion will be changed.

Signed-off-by: default avatarAnton Arapov <anton@redhat.com>
Acked-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
parent ea024870

kernel/events/uprobes.c

+25 −0
Original line number Original line Diff line number Diff line
@@ -1132,6 +1132,7 @@ static struct xol_area *get_xol_area(void) 
{

{

	struct mm_struct *mm = current->mm;

	struct mm_struct *mm = current->mm;

	struct xol_area *area;

	struct xol_area *area;

	uprobe_opcode_t insn = UPROBE_SWBP_INSN;





	area = mm->uprobes_state.xol_area;

	area = mm->uprobes_state.xol_area;

	if (area)

	if (area)
@@ -1149,7 +1150,12 @@ static struct xol_area *get_xol_area(void) 
	if (!area->page)

	if (!area->page)

		goto free_bitmap;

		goto free_bitmap;





	/* allocate first slot of task's xol_area for the return probes */

	set_bit(0, area->bitmap);

	copy_to_page(area->page, 0, &insn, UPROBE_SWBP_INSN_SIZE);

	atomic_set(&area->slot_count, 1);

	init_waitqueue_head(&area->wq);

	init_waitqueue_head(&area->wq);



	if (!xol_add_vma(area))

	if (!xol_add_vma(area))

		return area;

		return area;
@@ -1346,6 +1352,25 @@ static struct uprobe_task *get_utask(void) 
	return current->utask;

	return current->utask;

}

}





/*

 * Current area->vaddr notion assume the trampoline address is always

 * equal area->vaddr.

 *

 * Returns -1 in case the xol_area is not allocated.

 */

static unsigned long get_trampoline_vaddr(void)

{

	struct xol_area *area;

	unsigned long trampoline_vaddr = -1;



	area = current->mm->uprobes_state.xol_area;

	smp_read_barrier_depends();

	if (area)

		trampoline_vaddr = area->vaddr;



	return trampoline_vaddr;

}



/* Prepare to single-step probed instruction out of line. */

/* Prepare to single-step probed instruction out of line. */

static int

static int

pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long bp_vaddr)

pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long bp_vaddr)