Commit 9f68f672 authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

uprobes: Introduce MMF_RECALC_UPROBES 



Add the new MMF_RECALC_UPROBES flag, it means that MMF_HAS_UPROBES
can be false positive after remove_breakpoint() or uprobe_munmap().
It is also set by uprobe_dup_mmap(), this is not optimal but simple.
We could add the new hook, uprobe_dup_vma(), to set MMF_HAS_UPROBES
only if the new mm actually has uprobes, but I don't think this
makes sense.

The next patch will use this flag to clear MMF_HAS_UPROBES.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
parent 6f47caa0

include/linux/sched.h

+2 −1
Original line number Diff line number Diff line
@@ -446,7 +446,8 @@ extern int get_dumpable(struct mm_struct *mm); 
#define MMF_VM_HUGEPAGE		17	/* set when VM_HUGEPAGE is set on vma */

#define MMF_EXE_FILE_CHANGED	18	/* see prctl_set_mm_exe_file() */



#define MMF_HAS_UPROBES		19	/* might have uprobes */

#define MMF_HAS_UPROBES		19	/* has uprobes */

#define MMF_RECALC_UPROBES	20	/* MMF_HAS_UPROBES can be wrong */



#define MMF_INIT_MASK		(MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK)

kernel/events/uprobes.c

+35 −4
Original line number Diff line number Diff line
@@ -684,7 +684,9 @@ install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, 
		set_bit(MMF_HAS_UPROBES, &mm->flags);



	ret = set_swbp(&uprobe->arch, mm, vaddr);

	if (ret && first_uprobe)

	if (!ret)

		clear_bit(MMF_RECALC_UPROBES, &mm->flags);

	else if (first_uprobe)

		clear_bit(MMF_HAS_UPROBES, &mm->flags);



	return ret;
@@ -693,6 +695,11 @@ install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, 
static void

remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vaddr)

{

	/* can happen if uprobe_register() fails */

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

		return;



	set_bit(MMF_RECALC_UPROBES, &mm->flags);

	set_orig_insn(&uprobe->arch, mm, vaddr);

}
@@ -1026,6 +1033,25 @@ int uprobe_mmap(struct vm_area_struct *vma) 
	return 0;

}



static bool

vma_has_uprobes(struct vm_area_struct *vma, unsigned long start, unsigned long end)

{

	loff_t min, max;

	struct inode *inode;

	struct rb_node *n;



	inode = vma->vm_file->f_mapping->host;



	min = vaddr_to_offset(vma, start);

	max = min + (end - start) - 1;



	spin_lock(&uprobes_treelock);

	n = find_node_in_range(inode, min, max);

	spin_unlock(&uprobes_treelock);



	return !!n;

}



/*

 * Called in context of a munmap of a vma.

 */
@@ -1037,10 +1063,12 @@ void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned lon 
	if (!atomic_read(&vma->vm_mm->mm_users)) /* called by mmput() ? */

		return;



	if (!test_bit(MMF_HAS_UPROBES, &vma->vm_mm->flags))

	if (!test_bit(MMF_HAS_UPROBES, &vma->vm_mm->flags) ||

	     test_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags))

		return;



	/* TODO: unmapping uprobe(s) will need more work */

	if (vma_has_uprobes(vma, start, end))

		set_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags);

}



/* Slot allocation for XOL */
@@ -1146,8 +1174,11 @@ void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm) 
{

	newmm->uprobes_state.xol_area = NULL;



	if (test_bit(MMF_HAS_UPROBES, &oldmm->flags))

	if (test_bit(MMF_HAS_UPROBES, &oldmm->flags)) {

		set_bit(MMF_HAS_UPROBES, &newmm->flags);

		/* unconditionally, dup_mmap() skips VM_DONTCOPY vmas */

		set_bit(MMF_RECALC_UPROBES, &newmm->flags);

	}

}



/*

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