From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x227Ym1ywIm9TR0QurAXcH/Xy5DkdLZcB74D7iCdvalHSEuXbKxTX/mk6f/mNEcXkZsL1byWG ARC-Seal: i=1; a=rsa-sha256; t=1516900229; cv=none; d=google.com; s=arc-20160816; b=Ugx+L7C6gn1mO0GTYI4QJlrEBNbTx3upapY3k7K/AQb6TfyIAKGw8UCajBjKAIJTTI KkLnlaRJQH0EUX4e2q8GwTVWh3bYJg3HjqI3R1345v/JJWwGueBIZQrkNvhVKicWJbup 7TNGuOg8bb4oWRhM8zyKaz9sLjlsCku6a37NPhkemz/RTVN+VG1Bvrx4+Z7tkWO7sIcY 1aU2FRZCgwvywyzKTH1+nU7/wgNTRYeH4x/6+3ROy/QRC6f+vugD9qM2LH8MaX5gWxqR CmPj66+U1toiIBwZi4l/ZpFYFCGtEnPmKB8cJ+Z0WYikJaulYf3tvNpBdvw7Oubpu3IJ UnRw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:message-id:in-reply-to:subject :cc:to:from:date:arc-authentication-results; bh=JVQ4WE+nudv7p8XpRgPHdP0Mena384JP8gCoB0DRTb8=; b=oUxpFDNJevbyfb48LF5HLW3LjxBOzAeDcky+xZxejjQdkAvxGypba1dOhA12JqEflF 6LhMWjpgcBTPvdmJ7b13+FiQXNYRmIdkdM67Ow2X1/Ijnop+KU/io6fF2xPHMNyWSaxF 0OybD9h34qCMJlmWlWLU1B8A1LmS/u6q8FLJcHnPGfN8GBlxRK222ToID081iVbI5UZ3 5+q3RK//M6D9xlIuAIiwIVnetxVVbCuPsgnGDwR9xbR3R/F2pu+E4d5gJS0ofd4ehU31 xIwBnPBSpaIq7OaFfXgv2EcDcELvLcC7yKwaHXz5oRkAMWlrh2Vle/HpAUSP66N/pP/1 1dTQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of tglx@linutronix.de designates 2a01:7a0:2:106d:700::1 as permitted sender) smtp.mailfrom=tglx@linutronix.de Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of tglx@linutronix.de designates 2a01:7a0:2:106d:700::1 as permitted sender) smtp.mailfrom=tglx@linutronix.de Date: Thu, 25 Jan 2018 18:10:20 +0100 (CET) From: Thomas Gleixner To: David Woodhouse cc: Josh Poimboeuf , Borislav Petkov , tim.c.chen@linux.intel.com, pjt@google.com, jikos@kernel.org, gregkh@linux-foundation.org, dave.hansen@intel.com, mingo@kernel.org, riel@redhat.com, luto@amacapital.net, torvalds@linux-foundation.org, ak@linux.intel.com, keescook@google.com, peterz@infradead.org, hpa@zytor.com, linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org Subject: Re: [tip:x86/pti] x86/retpoline: Fill return stack buffer on vmexit In-Reply-To: <1516899639.30244.145.camel@infradead.org> Message-ID: References: <1515755487-8524-1-git-send-email-dwmw@amazon.co.uk> <20180125120743.ey32gvl5mjam4r2s@pd.tnic> <1516882849.30244.94.camel@infradead.org> <20180125124554.vdx7rrnfrxrzl2ng@pd.tnic> <20180125151024.bidjr26r667vs7h5@treble> <20180125155110.mw655b7fwgm7qqc7@pd.tnic> <1516896198.30244.133.camel@infradead.org> <20180125165646.ytc4upthpaqtwi45@treble> <1516899639.30244.145.camel@infradead.org> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: multipart/mixed; BOUNDARY="8323329-292357867-1516900220=:2020" X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1589334225298273984?= X-GMAIL-MSGID: =?utf-8?q?1590585174984465487?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323329-292357867-1516900220=:2020 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT On Thu, 25 Jan 2018, David Woodhouse wrote: > On Thu, 2018-01-25 at 10:56 -0600, Josh Poimboeuf wrote: > > On Thu, Jan 25, 2018 at 04:03:18PM +0000, David Woodhouse wrote: > > > On Thu, 2018-01-25 at 16:51 +0100, Borislav Petkov wrote: > > > >  > > > > > And the seg fault is objtool's way of telling you you need a > > > > > ANNOTATE_NOSPEC_ALTERNATIVE above the alternative ;-) > > > >  > > > > Except that it blew up when I did this which doesn't have ALTERNATIVE > > > > (it's the diff I saved :-)) > > >  > > > Yeah, ANNOTATE_NOSPEC_ALTERNATIVE just tells objtool "don't look at the > > > alternative; you're not going to like it". > > >  > > > If you start putting a __fill_rsb() function out of line somewhere and > > > only *calling* it from alternatives, then objtool is going to shit > > > itself when it sees that function, regardless. > > > > Right, if you *really* want it always inline, the short term solution is > > to just patch it in with X86_FEATURE_ALWAYS. > > And the whole problem here is that patching it in with alternatives is > painful on kernels < 4.1 because back then, we didn't cope with > oldinstr and altinstr being different lengths. > > And they don't want to fix *that* because kABI... > > I just stopped caring. Rightfully so. KABI has often enough proven to be complete garbage. If people still insist on it, it's _their_ problem not ours. Thanks, tglx --8323329-292357867-1516900220=:2020--