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Commit a6cb3f6d authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

uprobes: Do not play with utask in xol_get_insn_slot() 



pre_ssout()->xol_get_insn_slot() path is confusing and buggy. This patch
cleanups the code, the next one fixes the bug.

Change xol_get_insn_slot() to only allocate the slot and do nothing more,
move the initialization of utask->xol_vaddr/vaddr into pre_ssout().

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarAnton Arapov <anton@redhat.com>
Acked-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
parent 5a2df662

kernel/events/uprobes.c

+21 −16
Original line number Diff line number Diff line
@@ -1176,30 +1176,26 @@ static unsigned long xol_take_insn_slot(struct xol_area *area) 
}



/*

 * xol_get_insn_slot - If was not allocated a slot, then

 * allocate a slot.

 * xol_get_insn_slot - allocate a slot for xol.

 * Returns the allocated slot address or 0.

 */

static unsigned long xol_get_insn_slot(struct uprobe *uprobe, unsigned long slot_addr)

static unsigned long xol_get_insn_slot(struct uprobe *uprobe)

{

	struct xol_area *area;

	unsigned long offset;

	unsigned long xol_vaddr;

	void *vaddr;



	area = get_xol_area();

	if (!area)

		return 0;



	current->utask->xol_vaddr = xol_take_insn_slot(area);

	/*

	 * Initialize the slot if xol_vaddr points to valid

	 * instruction slot.

	 */

	if (unlikely(!current->utask->xol_vaddr))

	xol_vaddr = xol_take_insn_slot(area);

	if (unlikely(!xol_vaddr))

		return 0;



	current->utask->vaddr = slot_addr;

	offset = current->utask->xol_vaddr & ~PAGE_MASK;

	/* Initialize the slot */

	offset = xol_vaddr & ~PAGE_MASK;

	vaddr = kmap_atomic(area->page);

	memcpy(vaddr + offset, uprobe->arch.insn, MAX_UINSN_BYTES);

	kunmap_atomic(vaddr);
@@ -1209,7 +1205,7 @@ static unsigned long xol_get_insn_slot(struct uprobe *uprobe, unsigned long slot 
	 */

	flush_dcache_page(area->page);



	return current->utask->xol_vaddr;

	return xol_vaddr;

}



/*
@@ -1306,12 +1302,21 @@ static struct uprobe_task *get_utask(void) 


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

static int

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

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

{

	if (xol_get_insn_slot(uprobe, vaddr) && !arch_uprobe_pre_xol(&uprobe->arch, regs))

		return 0;

	struct uprobe_task *utask;

	unsigned long xol_vaddr;



	utask = current->utask;



	xol_vaddr = xol_get_insn_slot(uprobe);

	if (!xol_vaddr)

		return -ENOMEM;



	utask->xol_vaddr = xol_vaddr;

	utask->vaddr = bp_vaddr;



	return -EFAULT;

	return arch_uprobe_pre_xol(&uprobe->arch, regs);

}



/*