From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Woodhouse Subject: Re: xen/link: Move .data.rel.ro sections into .rodata for final link Date: Mon, 31 Jul 2017 12:02:20 +0100 Message-ID: <1501498940.4771.251.camel@infradead.org> References: <1500564043.4400.15.camel@infradead.org> <597D79BD0200007800102F92@prv-mh.provo.novell.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============4334335923539706056==" Return-path: Received: from mail6.bemta6.messagelabs.com ([193.109.254.103]) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dc8T0-0004aP-Ii for xen-devel@lists.xenproject.org; Mon, 31 Jul 2017 11:02:30 +0000 In-Reply-To: <597D79BD0200007800102F92@prv-mh.provo.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xen.org Sender: "Xen-devel" To: Jan Beulich Cc: xen-devel@lists.xenproject.org, Jiewen Yao , Jeff Fan List-Id: xen-devel@lists.xenproject.org --===============4334335923539706056== Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-R+QAtB41iOQl2dw591Fk" --=-R+QAtB41iOQl2dw591Fk Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Sun, 2017-07-30 at 00:16 -0600, Jan Beulich wrote: > >=20 > > >=20 > > > >=20 > > > > David Woodhouse 07/20/17 5:22 PM >>> > > This includes stuff lke the hypercall tables which we really want > > to be read-only. And they were going into .data.read-mostly. > Yes, we'd like them to be read-only, but what if EFI properly assigned r/= o > permissions to the .rodata section when loading xen.efi? We'd then be > unable to apply relocations when switching from 1:1 to virtual mappings > (see efi_arch_relocate_image()). FWIW it does look like TianoCore has gained the ability to mark sections as read-only, in January of this year: https://github.com/tianocore/edk2/commit/d0e92aad46 It doesn't actually seem to be complete =E2=80=94 even with subsequent fixe= s since that commit, it doesn't look like it catches the case of data sections without EFI_IMAGE_SCN_MEM_WRITE, such as .rodata.=C2=A0 And even if/when that gets fixed you'll note that the protection is deliberately torn down in ExitBootServices(), specifically for the case you're concerned about below =E2=80=94 because you'll need to do the relocations. So I don't think there should be a problem here. --=-R+QAtB41iOQl2dw591Fk Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCDzUw ggSvMIIDl6ADAgECAhEA4CPLFRKDU4mtYW56VGdrITANBgkqhkiG9w0BAQsFADBvMQswCQYDVQQG EwJTRTEUMBIGA1UEChMLQWRkVHJ1c3QgQUIxJjAkBgNVBAsTHUFkZFRydXN0IEV4dGVybmFsIFRU UCBOZXR3b3JrMSIwIAYDVQQDExlBZGRUcnVzdCBFeHRlcm5hbCBDQSBSb290MB4XDTE0MTIyMjAw MDAwMFoXDTIwMDUzMDEwNDgzOFowgZsxCzAJBgNVBAYTAkdCMRswGQYDVQQIExJHcmVhdGVyIE1h bmNoZXN0ZXIxEDAOBgNVBAcTB1NhbGZvcmQxGjAYBgNVBAoTEUNPTU9ETyBDQSBMaW1pdGVkMUEw PwYDVQQDEzhDT01PRE8gU0hBLTI1NiBDbGllbnQgQXV0aGVudGljYXRpb24gYW5kIFNlY3VyZSBF bWFpbCBDQTCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAImxDdp6UxlOcFIdvFamBia3 uEngludRq/HwWhNJFaO0jBtgvHpRQqd5jKQi3xdhTpHVdiMKFNNKAn+2HQmAbqUEPdm6uxb+oYep LkNSQxZ8rzJQyKZPWukI2M+TJZx7iOgwZOak+FaA/SokFDMXmaxE5WmLo0YGS8Iz1OlAnwawsayT 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