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Message-Id: <20080611132227.593b13ea.akpm@linux-foundation.org> Date: Wed, 11 Jun 2008 13:22:27 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: Peter Oberparleiter <peter.oberparleiter@...ibm.com> Cc: oberparleiter@...glemail.com, linux-kernel@...r.kernel.org, ltp-coverage@...ts.sourceforge.net, sam@...nborg.org Subject: Re: [PATCH 0/6] gcov kernel support On Wed, 11 Jun 2008 14:59:54 +0200 Peter Oberparleiter <peter.oberparleiter@...ibm.com> wrote: > Andrew Morton wrote: > > On Mon, 09 Jun 2008 15:49:16 +0200 Peter Oberparleiter <peter.oberparleiter@...ibm.com> wrote: > > > >> Andrew Morton wrote: > >> > On Mon, 02 Jun 2008 15:33:51 +0200 Peter Oberparleiter <peter.oberparleiter@...ibm.com> wrote: > >> > > >> >> This is version #3 of the gcov kernel support patch set > >> > > >> > My build tree is now filled with dead symlinks, like > >> > > >> > lrwxrwxrwx 1 akpm akpm 64 Jun 9 00:06 security/selinux/nlmsgtab.gcda -> /sys/kernel/debug/gcov/usr/src/25/security/selinux/nlmsgtab.gcda > >> > >> Unfortunately a necessary evil of this approach: symlinks are created > >> for all compiled source files while link targets are only available when > >> the corresponding code is executed. In other words: those links will be > >> dead for source files which don't compile to actual code and for modules > >> as long as they are not loaded. > > > > It doesn't seem awfully useful. I don't run kernels on my build > > machines and I'm sure many are in the same situation. So gcov is going > > to need a way of locating these files on the *target* machine. And > > once that is available, there is no need to add all these symlinks into > > the build directory. > > I don't see any other feasibly way to do it if we want the kernel to > work out-of-the-box with gcov. If the kernel was a user-space > application, gcc/libgcov would create the .gcda files in exactly the > same place where the symbolic links are now. > > If we removed those symlinks, users would have to manually copy files > from /sys on the test machine to the correct position in /objtree on the > build machine before being able to get any kind of result. This would > IMO reduce the usefulness of the gcov kernel infrastructure noticeably > (though gcov-wrappers such as lcov could be modified to hide the > additional effort). gcov needs both the .gcda files and the source tree available to do its work, I assume. So a sensible scenario would be to copy the entire build tree, including the .gcda symlinks over to the target system, yes? tar+scp+untar? If so, it'd be good to get that tested and documented... > How about a CONFIG_GCOV_PROFILE_SYMLINKS configuration option? What use would that be? > >> > Which causes (at least) > >> > > >> > ctags: Warning: cannot open source file "security/selinux/ss/conditional.gcda" : No such file or directory > >> > ctags: Warning: cannot open source file "security/selinux/netlink.gcda" : No such file or directory > >> > ctags: Warning: cannot open source file "security/selinux/netlabel.gcda" : No such file or directory > >> > >> > and probably other thing which I haven't discovered yet. > > I would argue that any mechanism that tries to access all files in > /objtree regardless of filename extension is brave at best, if not > broken. Well, these things happen. You'll probably need to add these to .gitignore. <does Samsummoning dance> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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