On Thu, May 27, 2021 at 02:31:12PM -0700, Kees Cook wrote: > On Wed, May 26, 2021 at 02:16:24PM -0700, Darrick J. Wong wrote: > > On Wed, May 26, 2021 at 01:21:06PM -0500, Gustavo A. R. Silva wrote: > > > > > > > > > On 4/20/21 18:56, Gustavo A. R. Silva wrote: > > > > > > > > > > > > On 4/20/21 18:38, Darrick J. Wong wrote: > > > >> On Tue, Apr 20, 2021 at 06:06:52PM -0500, Gustavo A. R. Silva wrote: > > > >>> In preparation to enable -Wimplicit-fallthrough for Clang, fix > > > >>> the following warnings by replacing /* fall through */ comments, > > > >>> and its variants, with the new pseudo-keyword macro fallthrough: > > > >>> > > > >>> fs/xfs/libxfs/xfs_alloc.c:3167:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/libxfs/xfs_da_btree.c:286:3: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/libxfs/xfs_ag_resv.c:346:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/libxfs/xfs_ag_resv.c:388:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/xfs_bmap_util.c:246:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/xfs_export.c:88:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/xfs_export.c:96:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/xfs_file.c:867:3: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/xfs_ioctl.c:562:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/xfs_ioctl.c:1548:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/xfs_iomap.c:1040:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/xfs_inode.c:852:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/xfs_log.c:2627:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/xfs_trans_buf.c:298:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/scrub/bmap.c:275:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/scrub/btree.c:48:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/scrub/common.c:85:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/scrub/common.c:138:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/scrub/common.c:698:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/scrub/dabtree.c:51:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> fs/xfs/scrub/repair.c:951:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] > > > >>> > > > >>> Notice that Clang doesn't recognize /* fall through */ comments as > > > >>> implicit fall-through markings, so in order to globally enable > > > >>> -Wimplicit-fallthrough for Clang, these comments need to be > > > >>> replaced with fallthrough; in the whole codebase. > > > >>> > > > >>> Link: https://github.com/KSPP/linux/issues/115 > > > >>> Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx> > > > >> > > > >> I've already NAKd this twice, so I guess I'll NAK it a third time. > > > > > > > > Darrick, > > > > > > > > The adoption of fallthrough; has been already accepted and in use since Linux v5.7: > > > > > > > > https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through > > > > > > > > This change is needed, and I would really prefer if this goes upstream through your tree. > > > > > > > > Linus has taken these patches directly for a while, now. > > > > > > > > Could you consider taking it this time? :) > > > > > > > > > > Hi Darrick, > > > > > > If you don't mind, I will take this in my -next[1] branch for v5.14, so we can globally enable > > > -Wimplicit-fallthrough for Clang in that release. > > > > > > We had thousands of these warnings and now we are down to 47 in next-20210526, > > > 22 of which are fixed with this patch. > > > > I guess we're all required to kowtow to a bunch of effing bots now. > > Hooray for having to have a macro to code-switch for the sake of > > stupid compiler writers who refuse to give the rest of us a single > > workable way to signal "this switch code block should not end here": > > > > /* fall through */ > > __attribute__((fallthrough)); > > do { } while (0) /* fall through */ > > > > and soon the ISO geniuses will make it worse by adding to C2x: > > > > [[fallthrough]]; > > > > Hooray! Macros to abstractify stupidity!!!! > > > > Dave and I have told you and Miaohe several[1] times[2] to fix[3] the > > compiler, but clearly you don't care what we think and have decided to > > ram this in through Linus anyway. > > To clarify, we certainly _do_ care what you think. It's just that > when faced with the difficulties of the compiler's implementations of > handling this, the kernel had to get creative and pick the least-bad of > many bad choices. The choices are bad, so **turn it off** in fs/xfs/Makefile and don't go making us clutter up shared library code that will then have to be ported to userspace. --D > We're trying to make the kernel safer for everyone, > and this particular C language weakness has caused us a significant > number of bugs. Eradicating it is worth the effort. > All that said, as you pointed out, you _have_ asked before[1] to just > have Linus take it without bothering you directly, so okay, that can be > done. Generally maintainers have wanted these changes to go through their > trees so it doesn't cause them merge pain, but it seems you'd prefer it > the other way around. > > -Kees > > [1] https://lore.kernel.org/linux-xfs/20200820191237.GK6096@magnolia/ > "If you feel really passionate about ramming a bunch of pointless churn > into the kernel tree to make my life more painful, send this to Linus > and let him make the change." > > > Since that is what you choose, do not send me email again. > > > > NAKed-by: Darrick J. Wong <djwong@xxxxxxxxxx> > > > > --D > > > > [1] https://lore.kernel.org/linux-xfs/20200820191237.GK6096@magnolia/ > > [2] https://lore.kernel.org/linux-xfs/20210420230652.GA70650@embeddedor/ > > [3] https://lore.kernel.org/linux-xfs/20200708065512.GN2005@xxxxxxxxxxxxxxxxxxx/ > > > > > > > > Thanks > > > -- > > > Gustavo > > > > > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux.git/log/?h=for-next/kspp > > -- > Kees Cook
