linux-kernel - Re: [PATCH 1/3] uprobes: install_breakpoint() should fail if is_swbp

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Message-ID: <20120601155312.GA20265@redhat.com>
Date:	Fri, 1 Jun 2012 17:53:12 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] uprobes: install_breakpoint() should fail if
	is_swbp_insn() == T

On 05/31, Oleg Nesterov wrote:
>
> __find_next_vma_info() checks tmpvi->mm == vma->vm_mm to detect the
> already visited mm/vma. However, afaics this can be false positive?

Yes, but I guess this is harmless, we can rely on uprobe_mmap.

But. Doesn't this mean we can greatly simplify register_for_each_vma()
and make it O(n) ?

Unless I missed something, we can simply create the list of
mm/vaddr structures under ->i_mmap_mutex (vma_prio_tree_foreach), then
register_for_each_vma() can process the list and that is all.

If another mapping comes after we drop i_mmap_mutex, uprobe_mmap()
should be called and it should install the bp.

Srikar, Peter, what do you think?

Oleg.

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