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Date:   Wed, 7 Apr 2021 15:26:21 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     Peter Oberparleiter <oberpar@linux.ibm.com>,
        Nathan Chancellor <nathan@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        Fangrui Song <maskray@google.com>,
        Prasad Sodagudi <psodagud@quicinc.com>,
        "# 3.4.x" <stable@vger.kernel.org>
Subject: Re: [PATCH 1/2] gcov: re-fix clang-11+ support
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On Wed, 7 Apr 2021 14:28:21 -0700 Nick Desaulniers <ndesaulniers@google.com> wrote:

> On Wed, Apr 7, 2021 at 2:21 PM Andrew Morton <akpm@linux-foundation.org> wrote:
> >
> > On Wed,  7 Apr 2021 11:54:55 -0700 Nick Desaulniers <ndesaulniers@google.com> wrote:
> >
> > > LLVM changed the expected function signature for
> > > llvm_gcda_emit_function() in the clang-11 release.  Users of clang-11 or
> > > newer may have noticed their kernels producing invalid coverage
> > > information:
> > >
> > > $ llvm-cov gcov -a -c -u -f -b <input>.gcda -- gcno=<input>.gcno
> > > 1 <func>: checksum mismatch, \
> > >   (<lineno chksum A>, <cfg chksum B>) != (<lineno chksum A>, <cfg chksum C>)
> > > 2 Invalid .gcda File!
> > > ...
> > >
> > > Fix up the function signatures so calling this function interprets its
> > > parameters correctly and computes the correct cfg checksum. In
> > > particular, in clang-11, the additional checksum is no longer optional.
> >
> > Which tree is this against?  I'm seeing quite a lot of rejects against
> > Linus's current.
> 
> Today's linux-next; the only recent changes to this single source file
> since my last patches were:
> 
> commit b3c4e66c908b ("gcov: combine common code")
> commit 17d0508a080d ("gcov: use kvmalloc()")
> 
> both have your sign off, so I assume those are in your tree?

Yes, I presently have

gcov-clang-drop-support-for-clang-10-and-older.patch
gcov-combine-common-code.patch
gcov-simplify-buffer-allocation.patch
gcov-use-kvmalloc.patch

But this patch ("gcov: re-fix clang-11+ support") has cc:stable, so it
should be against Linus's tree, to give the -stable trees something
more mergeable.