From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jani Nikula Date: Wed, 23 Jan 2019 16:23:39 +0200 Subject: [Intel-wired-lan] [Intel-gfx] [PATCH 1/3] treewide: Lift switch variables out of switches In-Reply-To: <874l9z31c5.fsf@intel.com> References: <20190123110349.35882-1-keescook@chromium.org> <20190123110349.35882-2-keescook@chromium.org> <20190123115829.GA31385@kroah.com> <874l9z31c5.fsf@intel.com> Message-ID: <871s53311w.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: intel-wired-lan@osuosl.org List-ID: On Wed, 23 Jan 2019, Jani Nikula wrote: > On Wed, 23 Jan 2019, Greg KH wrote: >> On Wed, Jan 23, 2019 at 03:03:47AM -0800, Kees Cook wrote: >>> Variables declared in a switch statement before any case statements >>> cannot be initialized, so move all instances out of the switches. >>> After this, future always-initialized stack variables will work >>> and not throw warnings like this: >>> >>> fs/fcntl.c: In function ?send_sigio_to_task?: >>> fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitch-unreachable] >>> siginfo_t si; >>> ^~ >> >> That's a pain, so this means we can't have any new variables in { } >> scope except for at the top of a function? >> >> That's going to be a hard thing to keep from happening over time, as >> this is valid C :( > > Not all valid C is meant to be used! ;) > > Anyway, I think you're mistaking the limitation to arbitrary blocks > while it's only about the switch block IIUC. > > Can't have: > > switch (i) { > int j; > case 0: > /* ... */ > } > > because it can't be turned into: > > switch (i) { > int j = 0; /* not valid C */ > case 0: > /* ... */ > } > > but can have e.g.: > > switch (i) { > case 0: > { > int j = 0; > /* ... */ > } > } > > I think Kees' approach of moving such variable declarations to the > enclosing block scope is better than adding another nesting block. PS. The patch is Reviewed-by: Jani Nikula and the drivers/gpu/drm/i915/* parts are Acked-by: Jani Nikula for merging via whichever tree is appropriate. (There'll be minor conflicts with in-flight work in our -next tree, but no biggie.) -- Jani Nikula, Intel Open Source Graphics Center From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jani Nikula Subject: Re: [Intel-gfx] [PATCH 1/3] treewide: Lift switch variables out of switches In-Reply-To: <874l9z31c5.fsf@intel.com> References: <20190123110349.35882-1-keescook@chromium.org> <20190123110349.35882-2-keescook@chromium.org> <20190123115829.GA31385@kroah.com> <874l9z31c5.fsf@intel.com> Date: Wed, 23 Jan 2019 16:23:39 +0200 Message-ID: <871s53311w.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable To: Greg KH , Kees Cook Cc: dev@openvswitch.org, Ard Biesheuvel , netdev@vger.kernel.org, intel-gfx@lists.freedesktop.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, kernel-hardening@lists.openwall.com, intel-wired-lan@lists.osuosl.org, linux-fsdevel@vger.kernel.org, xen-devel@lists.xenproject.org, Laura Abbott , linux-kbuild@vger.kernel.org, Alexander Popov List-ID: On Wed, 23 Jan 2019, Jani Nikula wrote: > On Wed, 23 Jan 2019, Greg KH wrote: >> On Wed, Jan 23, 2019 at 03:03:47AM -0800, Kees Cook wrote: >>> Variables declared in a switch statement before any case statements >>> cannot be initialized, so move all instances out of the switches. >>> After this, future always-initialized stack variables will work >>> and not throw warnings like this: >>>=20 >>> fs/fcntl.c: In function =E2=80=98send_sigio_to_task=E2=80=99: >>> fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitch-= unreachable] >>> siginfo_t si; >>> ^~ >> >> That's a pain, so this means we can't have any new variables in { } >> scope except for at the top of a function? >> >> That's going to be a hard thing to keep from happening over time, as >> this is valid C :( > > Not all valid C is meant to be used! ;) > > Anyway, I think you're mistaking the limitation to arbitrary blocks > while it's only about the switch block IIUC. > > Can't have: > > switch (i) { > int j; > case 0: > /* ... */ > } > > because it can't be turned into: > > switch (i) { > int j =3D 0; /* not valid C */ > case 0: > /* ... */ > } > > but can have e.g.: > > switch (i) { > case 0: > { > int j =3D 0; > /* ... */ > } > } > > I think Kees' approach of moving such variable declarations to the > enclosing block scope is better than adding another nesting block. PS. The patch is Reviewed-by: Jani Nikula and the drivers/gpu/drm/i915/* parts are Acked-by: Jani Nikula for merging via whichever tree is appropriate. (There'll be minor conflicts with in-flight work in our -next tree, but no biggie.) --=20 Jani Nikula, Intel Open Source Graphics Center From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Subject: [1/3] treewide: Lift switch variables out of switches From: Jani Nikula Message-Id: <871s53311w.fsf@intel.com> Date: Wed, 23 Jan 2019 16:23:39 +0200 To: Greg KH , Kees Cook Cc: dev@openvswitch.org, Ard Biesheuvel , netdev@vger.kernel.org, intel-gfx@lists.freedesktop.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, kernel-hardening@lists.openwall.com, intel-wired-lan@lists.osuosl.org, linux-fsdevel@vger.kernel.org, xen-devel@lists.xenproject.org, Laura Abbott , linux-kbuild@vger.kernel.org, Alexander Popov List-ID: T24gV2VkLCAyMyBKYW4gMjAxOSwgSmFuaSBOaWt1bGEgPGphbmkubmlrdWxhQGxpbnV4LmludGVs LmNvbT4gd3JvdGU6Cj4gT24gV2VkLCAyMyBKYW4gMjAxOSwgR3JlZyBLSCA8Z3JlZ2toQGxpbnV4 Zm91bmRhdGlvbi5vcmc+IHdyb3RlOgo+PiBPbiBXZWQsIEphbiAyMywgMjAxOSBhdCAwMzowMzo0 N0FNIC0wODAwLCBLZWVzIENvb2sgd3JvdGU6Cj4+PiBWYXJpYWJsZXMgZGVjbGFyZWQgaW4gYSBz d2l0Y2ggc3RhdGVtZW50IGJlZm9yZSBhbnkgY2FzZSBzdGF0ZW1lbnRzCj4+PiBjYW5ub3QgYmUg aW5pdGlhbGl6ZWQsIHNvIG1vdmUgYWxsIGluc3RhbmNlcyBvdXQgb2YgdGhlIHN3aXRjaGVzLgo+ Pj4gQWZ0ZXIgdGhpcywgZnV0dXJlIGFsd2F5cy1pbml0aWFsaXplZCBzdGFjayB2YXJpYWJsZXMg d2lsbCB3b3JrCj4+PiBhbmQgbm90IHRocm93IHdhcm5pbmdzIGxpa2UgdGhpczoKPj4+IAo+Pj4g ZnMvZmNudGwuYzogSW4gZnVuY3Rpb24g4oCYc2VuZF9zaWdpb190b190YXNr4oCZOgo+Pj4gZnMv ZmNudGwuYzo3Mzg6MTM6IHdhcm5pbmc6IHN0YXRlbWVudCB3aWxsIG5ldmVyIGJlIGV4ZWN1dGVk IFstV3N3aXRjaC11bnJlYWNoYWJsZV0KPj4+ICAgIHNpZ2luZm9fdCBzaTsKPj4+ICAgICAgICAg ICAgICBefgo+Pgo+PiBUaGF0J3MgYSBwYWluLCBzbyB0aGlzIG1lYW5zIHdlIGNhbid0IGhhdmUg YW55IG5ldyB2YXJpYWJsZXMgaW4geyB9Cj4+IHNjb3BlIGV4Y2VwdCBmb3IgYXQgdGhlIHRvcCBv ZiBhIGZ1bmN0aW9uPwo+Pgo+PiBUaGF0J3MgZ29pbmcgdG8gYmUgYSBoYXJkIHRoaW5nIHRvIGtl ZXAgZnJvbSBoYXBwZW5pbmcgb3ZlciB0aW1lLCBhcwo+PiB0aGlzIGlzIHZhbGlkIEMgOigKPgo+ IE5vdCBhbGwgdmFsaWQgQyBpcyBtZWFudCB0byBiZSB1c2VkISA7KQo+Cj4gQW55d2F5LCBJIHRo aW5rIHlvdSdyZSBtaXN0YWtpbmcgdGhlIGxpbWl0YXRpb24gdG8gYXJiaXRyYXJ5IGJsb2Nrcwo+ IHdoaWxlIGl0J3Mgb25seSBhYm91dCB0aGUgc3dpdGNoIGJsb2NrIElJVUMuCj4KPiBDYW4ndCBo YXZlOgo+Cj4gCXN3aXRjaCAoaSkgewo+IAkJaW50IGo7Cj4gCWNhc2UgMDoKPiAgICAgICAgIAkv KiAuLi4gKi8KPiAJfQo+Cj4gYmVjYXVzZSBpdCBjYW4ndCBiZSB0dXJuZWQgaW50bzoKPgo+IAlz d2l0Y2ggKGkpIHsKPiAJCWludCBqID0gMDsgLyogbm90IHZhbGlkIEMgKi8KPiAJY2FzZSAwOgo+ ICAgICAgICAgCS8qIC4uLiAqLwo+IAl9Cj4KPiBidXQgY2FuIGhhdmUgZS5nLjoKPgo+IAlzd2l0 Y2ggKGkpIHsKPiAJY2FzZSAwOgo+IAkJewo+IAkJCWludCBqID0gMDsKPiAJICAgICAgICAJLyog Li4uICovCj4gCQl9Cj4gCX0KPgo+IEkgdGhpbmsgS2VlcycgYXBwcm9hY2ggb2YgbW92aW5nIHN1 Y2ggdmFyaWFibGUgZGVjbGFyYXRpb25zIHRvIHRoZQo+IGVuY2xvc2luZyBibG9jayBzY29wZSBp cyBiZXR0ZXIgdGhhbiBhZGRpbmcgYW5vdGhlciBuZXN0aW5nIGJsb2NrLgoKUFMuIFRoZSBwYXRj aCBpcwoKUmV2aWV3ZWQtYnk6IEphbmkgTmlrdWxhIDxqYW5pLm5pa3VsYUBpbnRlbC5jb20+Cgph bmQgdGhlIGRyaXZlcnMvZ3B1L2RybS9pOTE1LyogcGFydHMgYXJlCgpBY2tlZC1ieTogSmFuaSBO aWt1bGEgPGphbmkubmlrdWxhQGludGVsLmNvbT4KCmZvciBtZXJnaW5nIHZpYSB3aGljaGV2ZXIg dHJlZSBpcyBhcHByb3ByaWF0ZS4gKFRoZXJlJ2xsIGJlIG1pbm9yCmNvbmZsaWN0cyB3aXRoIGlu LWZsaWdodCB3b3JrIGluIG91ciAtbmV4dCB0cmVlLCBidXQgbm8gYmlnZ2llLikK