Commit 6ffe8c7d authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Peter Zijlstra
Browse files

uprobes: simplify xol_take_insn_slot() and its caller 



The do / while (slot_nr >= UINSNS_PER_PAGE) loop in xol_take_insn_slot()
makes no sense, the checked condition is always true. Change this code
to use the "for (;;)" loop, this way we do not need to change slot_nr if
test_and_set_bit() fails.

Also, kill the unnecessary xol_vaddr != NULL check in xol_get_insn_slot(),
xol_take_insn_slot() never returns NULL.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240929144244.GA9480@redhat.com
parent 430af825

kernel/events/uprobes.c

+4 −13
Original line number Diff line number Diff line
@@ -1628,25 +1628,20 @@ void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm) 
 */

static unsigned long xol_take_insn_slot(struct xol_area *area)

{

	unsigned long slot_addr;

	int slot_nr;

	unsigned int slot_nr;



	do {

	for (;;) {

		slot_nr = find_first_zero_bit(area->bitmap, UINSNS_PER_PAGE);

		if (slot_nr < UINSNS_PER_PAGE) {

			if (!test_and_set_bit(slot_nr, area->bitmap))

				break;



			slot_nr = UINSNS_PER_PAGE;

			continue;

		}

		wait_event(area->wq, (atomic_read(&area->slot_count) < UINSNS_PER_PAGE));

	} while (slot_nr >= UINSNS_PER_PAGE);

	}



	slot_addr = area->vaddr + (slot_nr * UPROBE_XOL_SLOT_BYTES);

	atomic_inc(&area->slot_count);



	return slot_addr;

	return area->vaddr + slot_nr * UPROBE_XOL_SLOT_BYTES;

}



/*
@@ -1663,12 +1658,8 @@ static unsigned long xol_get_insn_slot(struct uprobe *uprobe) 
		return 0;



	xol_vaddr = xol_take_insn_slot(area);

	if (unlikely(!xol_vaddr))

		return 0;



	arch_uprobe_copy_ixol(area->page, xol_vaddr,

			      &uprobe->arch.ixol, sizeof(uprobe->arch.ixol));



	return xol_vaddr;

}