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Commit ec75fba9 authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

uprobes: Simplify is_swbp_at_addr(), remove stale comments 



After the previous change is_swbp_at_addr() is always called with
current->mm. Remove this check and move it close to its single caller.

Also, remove the obsolete comment about is_swbp_at_addr() and
uprobe_state.count.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
parent ed6f6a50

kernel/events/uprobes.c

+24 −49
Original line number Diff line number Diff line
@@ -282,32 +282,6 @@ put_old: 
	return ret;

}



static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)

{

	struct page *page;

	uprobe_opcode_t opcode;

	int result;



	if (current->mm == mm) {

		pagefault_disable();

		result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr,

								sizeof(opcode));

		pagefault_enable();



		if (likely(result == 0))

			goto out;

	}



	result = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL);

	if (result < 0)

		return result;



	copy_opcode(page, vaddr, &opcode);

	put_page(page);

 out:

	return is_swbp_insn(&opcode);

}



/**

 * set_swbp - store breakpoint at a given address.

 * @auprobe: arch specific probepoint information.
@@ -589,29 +563,6 @@ static int copy_insn(struct uprobe *uprobe, struct file *filp) 
	return __copy_insn(mapping, filp, uprobe->arch.insn, bytes, uprobe->offset);

}



/*

 * How mm->uprobes_state.count gets updated

 * uprobe_mmap() increments the count if

 * 	- it successfully adds a breakpoint.

 * 	- it cannot add a breakpoint, but sees that there is a underlying

 * 	  breakpoint (via a is_swbp_at_addr()).

 *

 * uprobe_munmap() decrements the count if

 * 	- it sees a underlying breakpoint, (via is_swbp_at_addr)

 * 	  (Subsequent uprobe_unregister wouldnt find the breakpoint

 * 	  unless a uprobe_mmap kicks in, since the old vma would be

 * 	  dropped just after uprobe_munmap.)

 *

 * uprobe_register increments the count if:

 * 	- it successfully adds a breakpoint.

 *

 * uprobe_unregister decrements the count if:

 * 	- it sees a underlying breakpoint and removes successfully.

 * 	  (via is_swbp_at_addr)

 * 	  (Subsequent uprobe_munmap wouldnt find the breakpoint

 * 	  since there is no underlying breakpoint after the

 * 	  breakpoint removal.)

 */

static int

install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,

			struct vm_area_struct *vma, unsigned long vaddr)
@@ -1389,6 +1340,30 @@ static void mmf_recalc_uprobes(struct mm_struct *mm) 
	clear_bit(MMF_HAS_UPROBES, &mm->flags);

}



static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)

{

	struct page *page;

	uprobe_opcode_t opcode;

	int result;



	pagefault_disable();

	result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr,

							sizeof(opcode));

	pagefault_enable();



	if (likely(result == 0))

		goto out;



	result = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL);

	if (result < 0)

		return result;



	copy_opcode(page, vaddr, &opcode);

	put_page(page);

 out:

	return is_swbp_insn(&opcode);

}



static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)

{

	struct mm_struct *mm = current->mm;