From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x224CW1zW/XXbDCautu4v/M02qaiLRyUlgw14uGjJiInrFBrGvxZDfnL7PLOnOlKCV7fUBQPu ARC-Seal: i=1; a=rsa-sha256; t=1516896217; cv=none; d=google.com; s=arc-20160816; b=AMGDGx6cC+W+UNzYYY5gFIJbuo+xnoqFwZSV8cmDjREDl6h/Od7eXuCJ7RYSaODSur fZ8nlrHkte2v/qOoh1g2FLq+G5WLWByx+wuXWfL2hTqQMMDZl+dn6as6Nq4nBSbwGHLb YLs+md+ERp6yotmFt5zNVt8hNcoLcedxhTtTZN2COweEUh2ex4ae+gJTPdWT23JEg6Vr G0FAgyLINSucDoHiRx3cJYoO3ugxko27c6hrePMDwjgwM5SPvxwhdnn06I/d391RuFb7 K7UeCQAoWOIWqXuQEhEhB4M9VLPA/9gbwN1TVhSJAHTW4n8FR951vftRUtIt5Kq1qIpR 5Vow== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:date:face:references:in-reply-to:cc:to:from:subject :message-id:dkim-signature:arc-authentication-results; bh=UC5wmIEchHyqhx+rBkgb4hgjYWxycStMtPO8XUfO/f8=; b=OnlriSMRsd1vNqW2niOO3pEbpYRosC5cqUFidrOYxoCQ8x/6LcYX2Xku2CbB3k567K BMB+JV/nRn9V/HrFywVQRqEO741P/KZq5Wye19/f0eIPFB7ivGC8rwSOtSFTrjlWkKAs u0LL6QDYYd1rdVx4ILDZSUQaLyLYTxI+wXppFeSumLWdSHM8V1q9xiug5Nmbr/V1/qBr JZSYFLaNShaZhtwdRWvY7lkEK0Gn2hiYGf3mrMgcZqOQkYTunzdblTeID0rzJv1iRZxn 3hlJKSq90EsCsS39Cqb0qWOLAyt/nSygrAD9JbN+W39W0mUjnid0QB3t+yRomPJWqMqU r+fw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@infradead.org header.s=twosheds.20170209 header.b=SYKXkNIV; spf=pass (google.com: best guess record for domain of batv+c81c304d53d4f47de05e+5268+infradead.org+dwmw2@twosheds.srs.infradead.org designates 2001:8b0:10b:1:21d:7dff:fe04:dbe2 as permitted sender) smtp.mailfrom=BATV+c81c304d53d4f47de05e+5268+infradead.org+dwmw2@twosheds.srs.infradead.org Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=twosheds.20170209 header.b=SYKXkNIV; spf=pass (google.com: best guess record for domain of batv+c81c304d53d4f47de05e+5268+infradead.org+dwmw2@twosheds.srs.infradead.org designates 2001:8b0:10b:1:21d:7dff:fe04:dbe2 as permitted sender) smtp.mailfrom=BATV+c81c304d53d4f47de05e+5268+infradead.org+dwmw2@twosheds.srs.infradead.org Message-ID: <1516896198.30244.133.camel@infradead.org> Subject: Re: [tip:x86/pti] x86/retpoline: Fill return stack buffer on vmexit From: David Woodhouse To: Borislav Petkov , Josh Poimboeuf Cc: 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, tglx@linutronix.de, hpa@zytor.com, linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org In-Reply-To: <20180125155110.mw655b7fwgm7qqc7@pd.tnic> 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> Face: 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 Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-6Wh2KbwqevQHojqWVz3Z" Date: Thu, 25 Jan 2018 16:03:18 +0000 Mime-Version: 1.0 X-Mailer: Evolution 3.18.5.2-0ubuntu3.2 X-SRS-Rewrite: SMTP reverse-path rewritten from by twosheds.infradead.org. See http://www.infradead.org/rpr.html X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1589334225298273984?= X-GMAIL-MSGID: =?utf-8?q?1590580967872792912?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: --=-6Wh2KbwqevQHojqWVz3Z Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2018-01-25 at 16:51 +0100, Borislav Petkov wrote: >=20 > > And the seg fault is objtool's way of telling you you need a > > ANNOTATE_NOSPEC_ALTERNATIVE above the alternative ;-) >=20 > 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. --=-6Wh2KbwqevQHojqWVz3Z Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCEFQw ggUxMIIEGaADAgECAhBNRhEyk/HZ7naOeTHWrzuAMA0GCSqGSIb3DQEBCwUAMIGXMQswCQYDVQQG EwJHQjEbMBkGA1UECBMSR3JlYXRlciBNYW5jaGVzdGVyMRAwDgYDVQQHEwdTYWxmb3JkMRowGAYD VQQKExFDT01PRE8gQ0EgTGltaXRlZDE9MDsGA1UEAxM0Q09NT0RPIFJTQSBDbGllbnQgQXV0aGVu dGljYXRpb24gYW5kIFNlY3VyZSBFbWFpbCBDQTAeFw0xNzEyMjEwMDAwMDBaFw0xODEyMjEyMzU5 NTlaMCQxIjAgBgkqhkiG9w0BCQEWE2R3bXcyQGluZnJhZGVhZC5vcmcwggEiMA0GCSqGSIb3DQEB AQUAA4IBDwAwggEKAoIBAQDgzLNWa18DNpGUj/ZeH0Sgz53ESIbzdPw3OJeuNP6jZhxZojbyfxbM hETscxI/Hj6UZ4a7sHm5BkVjlsB1Af2Za/PXUt8MmLAcPMHkMPGunvkUibEvblDvpqMkQZlaZM+t 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