From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Jann Horn <jannh@google.com>, Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
the arch/x86 maintainers <x86@kernel.org>,
kernel list <linux-kernel@vger.kernel.org>,
alexandre.chartre@oracle.com
Subject: Re: x86 entry perf unwinding failure (missing IRET_REGS annotation on stack switch?)
Date: Tue, 28 Apr 2020 11:33:27 -0500 [thread overview]
Message-ID: <20200428163327.br43qcontatbrxlf@treble> (raw)
In-Reply-To: <20200428162551.GF12735@linux.intel.com>
On Tue, Apr 28, 2020 at 09:25:51AM -0700, Sean Christopherson wrote:
> On Tue, Apr 28, 2020 at 10:54:13AM -0500, Josh Poimboeuf wrote:
> > On Tue, Apr 28, 2020 at 10:49:09AM -0500, Josh Poimboeuf wrote:
> > > On Tue, Apr 28, 2020 at 05:25:52PM +0200, Peter Zijlstra wrote:
> > > > On Tue, Apr 28, 2020 at 09:31:57AM -0500, Josh Poimboeuf wrote:
> > > > > That's quite the monstrosity, and I still don't see the point. I
> > > > > thought we decided to just disallow CFI changes in alternatives anyway?
> > > > > That can be done much simpler.
> > > >
> > > > Something like so then ?
> > > >
> > > > ---
> > > > diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> > > > index 8443ec690051..d14d83e6edb0 100644
> > > > --- a/tools/objtool/check.c
> > > > +++ b/tools/objtool/check.c
> > > > @@ -940,6 +940,7 @@ static int handle_group_alt(struct objtool_file *file,
> > > >
> > > > last_new_insn = insn;
> > > >
> > > > + insn->alt_group = true;
> > > > insn->ignore = orig_insn->ignore_alts;
> > > > insn->func = orig_insn->func;
> > > >
> > > > @@ -2242,6 +2243,11 @@ static int handle_insn_ops(struct instruction *insn, struct insn_state *state)
> > > > list_for_each_entry(op, &insn->stack_ops, list) {
> > > > int res;
> > > >
> > > > + if (insn->alt_group) {
> > > > + WARN_FUNC("alternative has CFI", insn->sec, insn->offset);
> > > > + return 1;
> > > > + }
> > > > +
> > >
> > > ACK (separate patch)
> >
> > BTW, since most people don't know what CFI is, how about something like
> >
> > "unsupported stack change in alternatives code"
>
> Would it be accurate to print
>
> "unsupported CFI stack change in alternatives code"?
>
> to give the developer something more explicit to plug into their search
> engine?
I don't have a strong opinion either way, though this warning is going
to be documented in stack-validation.txt anyway right Peter? :-)
--
Josh
next prev parent reply other threads:[~2020-04-28 16:33 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-01 6:02 x86 entry perf unwinding failure (missing IRET_REGS annotation on stack switch?) Jann Horn
2020-03-02 14:58 ` Peter Zijlstra
2020-03-02 15:18 ` Josh Poimboeuf
2020-03-02 15:52 ` Josh Poimboeuf
2020-04-28 7:04 ` Josh Poimboeuf
2020-04-28 12:46 ` Peter Zijlstra
2020-04-28 14:14 ` Josh Poimboeuf
2020-04-28 14:35 ` Peter Zijlstra
2020-04-28 14:16 ` Peter Zijlstra
2020-04-28 14:31 ` Josh Poimboeuf
2020-04-28 15:25 ` Peter Zijlstra
2020-04-28 15:49 ` Josh Poimboeuf
2020-04-28 15:54 ` Josh Poimboeuf
2020-04-28 16:25 ` Sean Christopherson
2020-04-28 16:33 ` Josh Poimboeuf [this message]
2020-04-28 18:28 ` Peter Zijlstra
2020-04-28 16:44 ` Peter Zijlstra
2020-04-28 17:01 ` Josh Poimboeuf
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