linux-kernel - Re: [PATCH] selftests/seccomp: fix build on older kernels

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Date:   Fri, 30 Aug 2019 09:19:00 -0600
From:   shuah <shuah@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Tycho Andersen <tycho@...ho.ws>, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Alakesh Haloi <alakesh.haloi@...il.com>,
        shuah <shuah@...nel.org>
Subject: Re: [PATCH] selftests/seccomp: fix build on older kernels

On 8/29/19 6:45 PM, shuah wrote:
> On 8/29/19 11:06 AM, Kees Cook wrote:
>> On Mon, Aug 26, 2019 at 08:43:02AM -0600, Tycho Andersen wrote:
>>> The seccomp selftest goes to some length to build against older kernel
>>> headers, viz. all the #ifdefs at the beginning of the file. 201766a20e30
>>> ("ptrace: add PTRACE_GET_SYSCALL_INFO request") introduces some 
>>> additional
>>> macros, but doesn't do the #ifdef dance. Let's add that dance here to
>>> avoid:
>>>
>>> gcc -Wl,-no-as-needed -Wall  seccomp_bpf.c -lpthread -o seccomp_bpf
>>> In file included from seccomp_bpf.c:51:
>>> seccomp_bpf.c: In function ‘tracer_ptrace’:
>>> seccomp_bpf.c:1787:20: error: ‘PTRACE_EVENTMSG_SYSCALL_ENTRY’ 
>>> undeclared (first use in this function); did you mean 
>>> ‘PTRACE_EVENT_CLONE’?
>>>    EXPECT_EQ(entry ? PTRACE_EVENTMSG_SYSCALL_ENTRY
>>>                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>> ../kselftest_harness.h:608:13: note: in definition of macro ‘__EXPECT’
>>>    __typeof__(_expected) __exp = (_expected); \
>>>               ^~~~~~~~~
>>> seccomp_bpf.c:1787:2: note: in expansion of macro ‘EXPECT_EQ’
>>>    EXPECT_EQ(entry ? PTRACE_EVENTMSG_SYSCALL_ENTRY
>>>    ^~~~~~~~~
>>> seccomp_bpf.c:1787:20: note: each undeclared identifier is reported 
>>> only once for each function it appears in
>>>    EXPECT_EQ(entry ? PTRACE_EVENTMSG_SYSCALL_ENTRY
>>>                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>> ../kselftest_harness.h:608:13: note: in definition of macro ‘__EXPECT’
>>>    __typeof__(_expected) __exp = (_expected); \
>>>               ^~~~~~~~~
>>> seccomp_bpf.c:1787:2: note: in expansion of macro ‘EXPECT_EQ’
>>>    EXPECT_EQ(entry ? PTRACE_EVENTMSG_SYSCALL_ENTRY
>>>    ^~~~~~~~~
>>> seccomp_bpf.c:1788:6: error: ‘PTRACE_EVENTMSG_SYSCALL_EXIT’ 
>>> undeclared (first use in this function); did you mean 
>>> ‘PTRACE_EVENT_EXIT’?
>>>      : PTRACE_EVENTMSG_SYSCALL_EXIT, msg);
>>>        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>> ../kselftest_harness.h:608:13: note: in definition of macro ‘__EXPECT’
>>>    __typeof__(_expected) __exp = (_expected); \
>>>               ^~~~~~~~~
>>> seccomp_bpf.c:1787:2: note: in expansion of macro ‘EXPECT_EQ’
>>>    EXPECT_EQ(entry ? PTRACE_EVENTMSG_SYSCALL_ENTRY
>>>    ^~~~~~~~~
>>> make: *** [Makefile:12: seccomp_bpf] Error 1
>>>
>>> Signed-off-by: Tycho Andersen <tycho@...ho.ws>
>>> Fixes: 201766a20e30 ("ptrace: add PTRACE_GET_SYSCALL_INFO request")
>>
>> Acked-by: Kees Cook <keescook@...omium.org>
>>
>> Alakesh Haloi also sent a fix[1] for this. I prefer Tycho's solution
>> (one #ifndef and a Fixes line). Shuah, can you please apply this?
>>
> 
> Kees,
> 
> Yes I will pick this up.
> 
> thanks,
> -- Shuah
> 

Applied after fixing the following checkpatch error in the commit log:

ERROR: Please use git commit description style 'commit <12+ chars of 
sha1> ("<title line>")' - ie: 'commit 201766a20e30 ("ptrace: add 
PTRACE_GET_SYSCALL_INFO request")'
#82:

Now reads as follows:

Commit 201766a20e30 ("ptrace: add PTRACE_GET_SYSCALL_INFO request")
     introduces some additional macros, but doesn't do the #ifdef dance.
     Let's add that dance here to avoid:

thanks,
-- Shuah