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Date: Sat, 13 Jan 2018 11:20:08 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Andy Lutomirski <luto@kernel.org>
Cc: X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Borislav Petkov <bp@alien8.de>,
        Kees Cook <keescook@chromium.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Hugh Dickins <hughd@google.com>,
        stable <stable@vger.kernel.org>
Subject: Re: [PATCH] selftests/x86: Add test_vsyscall
Message-ID: <20180113102008.prnjjbzr27rjryxw@gmail.com>
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* Andy Lutomirski <luto@kernel.org> wrote:

> On Fri, Jan 12, 2018 at 4:57 AM, Ingo Molnar <mingo@kernel.org> wrote:
> >
> > * Andy Lutomirski <luto@kernel.org> wrote:
> >
> >> tools/testing/selftests/x86/Makefile        |   2 +-
> >>  tools/testing/selftests/x86/test_vsyscall.c | 500 ++++++++++++++++++++++++++++
> >>  2 files changed, 501 insertions(+), 1 deletion(-)
> >>  create mode 100644 tools/testing/selftests/x86/test_vsyscall.c
> >
> > Hm, it doesn't even build here, on Ubuntu latest (Artful):
> >
> > triton:~/tip/tools/testing/selftests/x86> make test_vsyscall
> > gcc -O2 -g -std=gnu99 -pthread -Wall -no-pie    test_vsyscall.c   -o test_vsyscall
> > /tmp/ccKyelfb.o: In function `init_vdso':
> > /home/mingo/tip/tools/testing/selftests/x86/test_vsyscall.c:68: undefined reference to `dlopen'
> > /home/mingo/tip/tools/testing/selftests/x86/test_vsyscall.c:76: undefined reference to `dlsym'
> > /home/mingo/tip/tools/testing/selftests/x86/test_vsyscall.c:80: undefined reference to `dlsym'
> > /home/mingo/tip/tools/testing/selftests/x86/test_vsyscall.c:84: undefined reference to `dlsym'
> > /home/mingo/tip/tools/testing/selftests/x86/test_vsyscall.c:88: undefined reference to `dlsym'
> > /home/mingo/tip/tools/testing/selftests/x86/test_vsyscall.c:70: undefined reference to `dlopen'
> > collect2: error: ld returned 1 exit status
> > <builtin>: recipe for target 'test_vsyscall' failed
> > make: *** [test_vsyscall] Error 1
> >
> 
> You're not supposed to do that :)  The targets are test_vsyscall_32
> and test_vsyscall_64 or just plain make.  I think you're just ending
> up with make's default rule to try to build it and it's not working.

D'oh, of course! :-)

> We could try adding something like:
> 
> # The x86 selftests have files like foo.c that don't produce binaries
> # called foo (they're foo_32 and foo_64 instead).  Prevent confusion
> # if someone types 'make foo'.
> % : %.c
> % : %.o
> 
> to tools/testing/selftests/x86/Makefile, but that's a bit gross.

Well, we could make it to produce the proper targets, which wouldn't be gross.

But it's probably overkill - I've applied your patch.

Thanks,

	Ingo