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Date: Tue, 3 Dec 2013 21:01:47 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>, Peter Zijlstra <peterz@infradead.org>,
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        Andi Kleen <ak@linux.intel.com>, Ingo Molnar <mingo@kernel.org>,
        Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH?] uprobes: change uprobe_write_opcode() to modify the
	page directly
Message-ID: <20131203200147.GB19083@redhat.com>
References: <1385426236-14960-1-git-send-email-andi@firstfloor.org> <20131129183558.GA9803@redhat.com> <20131129195419.GB17656@two.firstfloor.org> <20131129200532.GA13561@redhat.com> <alpine.LRH.2.00.1311300023070.9932@twin.jikos.cz> <CA+55aFxJGidV4=ot0z_Va8+y2QWTDYghTm1Gin84StZ+R1SfXg@mail.gmail.com> <20131203184909.GA17571@redhat.com> <CA+55aFw3N=iNW2Ej6w7oksX5JDVis7QL=9X9D7JB_tKZhrjsLw@mail.gmail.com> <529E2F0C.8070405@zytor.com>
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On 12/03, H. Peter Anvin wrote:
>
> I guess it would have to be checked, but I would be *highly* surprised
> if UPROBE_SWBP_INSN_SIZE ever[1] could be anything than the fundamental
> instruction quantum, which means it should never be able to wrap a page,

Yes, it can't.

> but *also* should mean it should be able to just be put_user()'d

put_user() obviously can't work, we need access_remote_vm-like code.

> followed by whatever synchronization necessary to make it globally visible.

Could you explain what this synchronization should actually do ?

Oleg.