From: Oleg Nesterov <oleg@redhat.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
"David S. Miller" <davem@davemloft.net>, X86 ML <x86@kernel.org>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Subject: Re: Why do kprobes and uprobes singlestep?
Date: Tue, 2 Mar 2021 21:28:07 +0100 [thread overview]
Message-ID: <20210302202806.GB21871@redhat.com> (raw)
In-Reply-To: <CALCETrU2Rc4ejSoYyWgbk00U8tSc=aZDaj0mm+Ep62wOirZG7g@mail.gmail.com>
forgot to add Srikar, sorry for resend...
On 03/01, Andy Lutomirski wrote:
>
> On Mon, Mar 1, 2021 at 8:51 AM Oleg Nesterov <oleg@redhat.com> wrote:
> >
> > But I guess this has nothing to do with uprobes, they do not single-step
> > in kernel mode, right?
>
> They single-step user code, though, and the code that makes this work
> is quite ugly. Single-stepping on x86 is a mess.
But this doesn't really differ from, say, gdb doing si ? OK, except uprobes
have to hook DIE_DEBUG. Nevermind...
> > > Uprobes seem to single-step user code for no discernable reason.
> > > (They want to trap after executing an out of line instruction, AFAICT.
> > > Surely INT3 or even CALL after the out-of-line insn would work as well
> > > or better.)
> >
> > Uprobes use single-step from the very beginning, probably because this
> > is the most simple and "standard" way to implement xol.
> >
> > And please note that CALL/JMP/etc emulation was added much later to fix the
> > problems with non-canonical addresses, and this emulation it still incomplete.
>
> Is there something like a uprobe test suite?
Afaik, no.
> How maintained /
Add Srikar who sent the initial implementation. I can only say that I am glad that
./scripts/get_maintainer.pl no longer mentions me ;) I did some changes (including
emulation) but a) this was a long ago and b) only because I was forced^W asked to
fix the numerous bugs in this code.
> actively used is uprobe?
I have no idea, sorry ;)
Oleg.
next prev parent reply other threads:[~2021-03-02 22:37 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-23 23:24 Why do kprobes and uprobes singlestep? Andy Lutomirski
2021-02-24 1:17 ` Masami Hiramatsu
2021-02-24 19:45 ` Andy Lutomirski
2021-02-25 2:22 ` Masami Hiramatsu
2021-02-25 6:03 ` Andy Lutomirski
2021-02-25 9:11 ` Masami Hiramatsu
2021-03-01 14:08 ` [RFC PATCH 0/1] x86/kprobes: Remoev single-step trap from x86 kprobes Masami Hiramatsu
2021-03-01 14:08 ` [RFC PATCH 1/1] x86/kprobes: Use int3 instead of debug trap for single-step Masami Hiramatsu
2021-03-02 8:06 ` Peter Zijlstra
2021-03-02 8:38 ` Peter Zijlstra
2021-03-02 8:41 ` Peter Zijlstra
2021-03-02 8:54 ` Peter Zijlstra
2021-03-02 12:51 ` Masami Hiramatsu
2021-03-02 13:58 ` Peter Zijlstra
2021-03-02 15:25 ` [PATCH -tip 0/3] x86/kprobes: Remoev single-step trap from x86 kprobes Masami Hiramatsu
2021-03-02 15:25 ` [PATCH -tip 1/3] x86/kprobes: Retrieve correct opcode for group instruction Masami Hiramatsu
2021-03-23 15:15 ` [tip: x86/core] " tip-bot2 for Masami Hiramatsu
2021-03-02 15:25 ` [PATCH -tip 2/3] x86/kprobes: Identify far indirect JMP correctly Masami Hiramatsu
2021-03-23 15:15 ` [tip: x86/core] " tip-bot2 for Masami Hiramatsu
2021-03-02 15:25 ` [PATCH -tip 3/3] x86/kprobes: Use int3 instead of debug trap for single-step Masami Hiramatsu
2021-03-23 15:15 ` [tip: x86/core] " tip-bot2 for Masami Hiramatsu
2021-03-17 14:55 ` [PATCH -tip 0/3] x86/kprobes: Remoev single-step trap from x86 kprobes Masami Hiramatsu
2021-03-17 16:26 ` Peter Zijlstra
2021-03-17 17:45 ` Andy Lutomirski
2021-02-25 9:59 ` Why do kprobes and uprobes singlestep? Peter Zijlstra
2021-03-01 16:51 ` Oleg Nesterov
2021-03-02 1:36 ` Andy Lutomirski
2021-03-02 20:24 ` Alexei Starovoitov
2021-03-02 21:02 ` Andy Lutomirski
2021-03-03 1:22 ` Alexei Starovoitov
2021-03-03 1:46 ` Andy Lutomirski
2021-03-03 2:18 ` Alexei Starovoitov
2021-03-03 13:27 ` Oleg Nesterov
2021-03-03 18:11 ` Daniel Xu
2021-03-03 19:14 ` Andy Lutomirski
2021-03-02 20:25 ` Oleg Nesterov
2021-03-02 20:35 ` Andy Lutomirski
2021-03-02 20:28 ` Oleg Nesterov [this message]
2021-03-02 2:22 ` Masami Hiramatsu
2021-03-02 2:48 ` Andy Lutomirski
2021-03-02 20:31 ` Oleg Nesterov
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