From: Miroslav Benes <mbenes@suse.cz>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Borislav Petkov <bp@suse.de>, Dave Hansen <dave.hansen@intel.com>,
x86-ml <x86@kernel.org>, lkml <linux-kernel@vger.kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
live-patching@vger.kernel.org
Subject: Re: [GIT PULL] x86/urgent for v5.11-rc7
Date: Tue, 9 Feb 2021 16:16:05 +0100 (CET) [thread overview]
Message-ID: <alpine.LSU.2.21.2102091613320.31501@pobox.suse.cz> (raw)
In-Reply-To: <20210209094953.65d2f322@gandalf.local.home>
On Tue, 9 Feb 2021, Steven Rostedt wrote:
> On Tue, 9 Feb 2021 09:32:34 +0100 (CET)
> Miroslav Benes <mbenes@suse.cz> wrote:
>
> > powerpc has this
> >
> > static inline unsigned long klp_get_ftrace_location(unsigned long faddr)
> > {
> > /*
> > * Live patch works only with -mprofile-kernel on PPC. In this case,
> > * the ftrace location is always within the first 16 bytes.
> > */
> > return ftrace_location_range(faddr, faddr + 16);
> > }
> >
> > > > I suppose the trivial fix is to see if it points to endbr64 and if so,
> > > > increment the addr by the length of that.
> > >
> > > I thought of that too. But one thing that may be possible, is to use
> > > kallsym. I believe you can get the range of a function (start and end of
> > > the function) from kallsyms. Then ask ftrace for the addr in that range
> > > (there should only be one).
> >
> > And we can do this if a hard-coded value live above is not welcome. If I
> > remember correctly, we used to have exactly this in the old versions of
> > kGraft. We walked through all ftrace records, called
> > kallsyms_lookup_size_offset() on every record's ip and if the offset+ip
> > matched faddr (in this case), we returned the ip.
>
> Either way is fine. Question is, should we just wait till CET is
> implemented for the kernel before making any of these changes? Just knowing
> that we have a solution to handle it may be good enough for now.
I'd prefer it to be a part of CET enablement patch set.
Miroslav
next prev parent reply other threads:[~2021-02-09 15:16 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210207104022.GA32127@zn.tnic>
[not found] ` <CAHk-=widXSyJ8W3vRrqO-zNP12A+odxg2J2_-oOUskz33wtfqA@mail.gmail.com>
[not found] ` <20210207175814.GF32127@zn.tnic>
[not found] ` <CAHk-=wi5z9S7x94SKYNj6qSHBqz+OD76GW=MDzo-KN2Fzm-V4Q@mail.gmail.com>
[not found] ` <20210207224540.ercf5657pftibyaw@treble>
[not found] ` <20210208100206.3b74891e@gandalf.local.home>
2021-02-08 15:33 ` [GIT PULL] x86/urgent for v5.11-rc7 Josh Poimboeuf
2021-02-08 15:47 ` Peter Zijlstra
2021-02-08 16:15 ` Steven Rostedt
2021-02-09 8:32 ` Miroslav Benes
2021-02-09 14:49 ` Steven Rostedt
2021-02-09 15:16 ` Miroslav Benes [this message]
2021-02-09 16:45 ` Alexei Starovoitov
2021-02-09 16:55 ` Andy Lutomirski
2021-02-09 18:09 ` Linus Torvalds
2021-02-09 18:26 ` Andy Lutomirski
2021-02-09 18:39 ` Linus Torvalds
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