linux-kernel - Re: [PATCH] selftests/seccomp: sh: Fix register names

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Date:   Tue, 17 Nov 2020 23:57:20 +0100
From:   John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To:     Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org
Cc:     Michael Karcher <kernel@...rcher.dialup.fu-berlin.de>,
        Rich Felker <dalias@...c.org>,
        Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH] selftests/seccomp: sh: Fix register names

On 11/17/20 9:56 PM, Kees Cook wrote:
> It looks like the seccomp selftests were never actually built for sh.
> This fixes it, though I don't have an environment to do a runtime test
> of it yet.
> 
> Fixes: 0bb605c2c7f2b4b3 ("sh: Add SECCOMP_FILTER")
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  tools/testing/selftests/seccomp/seccomp_bpf.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
> index 7f7ecfcd66db..26c72f2b61b1 100644
> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
> @@ -1804,8 +1804,8 @@ TEST_F(TRACE_poke, getpid_runs_normally)
>  #define SYSCALL_RET(_regs)	(_regs).a[(_regs).windowbase * 4 + 2]
>  #elif defined(__sh__)
>  # define ARCH_REGS		struct pt_regs
> -# define SYSCALL_NUM(_regs)	(_regs).gpr[3]
> -# define SYSCALL_RET(_regs)	(_regs).gpr[0]
> +# define SYSCALL_NUM(_regs)	(_regs).regs[3]
> +# define SYSCALL_RET(_regs)	(_regs).regs[0]
>  #else
>  # error "Do not know how to find your architecture's registers and syscalls"
>  #endif

Yes, this fix is indeed necessary. However, there is another build issue that I ran into
and I'm not sure why it happens, but commenting out "#include <linux/sched.h>" in
../clone3/clone3_selftests.h fixes it.

root@...pitz:..selftests/seccomp> make
gcc -Wl,-no-as-needed -Wall  -lpthread  seccomp_bpf.c /usr/src/linux-5.9.8/tools/testing/selftests/kselftest_harness.h /usr/src/linux-5.9.8/tools/testing/selftests/kselftest.h  -o /usr/src/linux-5.9.8/tools/testing/selftests/seccomp/seccomp_bpf
In file included from seccomp_bpf.c:55:
../clone3/clone3_selftests.h:28:8: error: redefinition of ‘struct clone_args’
   28 | struct clone_args {
      |        ^~~~~~~~~~
In file included from ../clone3/clone3_selftests.h:8,
                 from seccomp_bpf.c:55:
/usr/include/linux/sched.h:92:8: note: originally defined here
   92 | struct clone_args {
      |        ^~~~~~~~~~
make: *** [../lib.mk:140: /usr/src/linux-5.9.8/tools/testing/selftests/seccomp/seccomp_bpf] Error 1
root@...pitz:..selftests/seccomp>

Your actual register naming fix is correct in any case as without your patch, building the seccomp
selftest fails with:

seccomp_bpf.c: In function ‘get_syscall’:
seccomp_bpf.c:1741:37: error: ‘struct pt_regs’ has no member named ‘gpr’; did you mean ‘pr’?
 1741 | # define SYSCALL_NUM(_regs) (_regs).gpr[3]
      |                                     ^~~
seccomp_bpf.c:1794:9: note: in expansion of macro ‘SYSCALL_NUM’
 1794 |  return SYSCALL_NUM(regs);
      |         ^~~~~~~~~~~
seccomp_bpf.c: In function ‘change_syscall’:
seccomp_bpf.c:1741:37: error: ‘struct pt_regs’ has no member named ‘gpr’; did you mean ‘pr’?
 1741 | # define SYSCALL_NUM(_regs) (_regs).gpr[3]
      |                                     ^~~
seccomp_bpf.c:1817:3: note: in expansion of macro ‘SYSCALL_NUM’
 1817 |   SYSCALL_NUM(regs) = syscall;
      |   ^~~~~~~~~~~
seccomp_bpf.c:1742:37: error: ‘struct pt_regs’ has no member named ‘gpr’; did you mean ‘pr’?
 1742 | # define SYSCALL_RET(_regs) (_regs).gpr[0]
      |                                     ^~~
seccomp_bpf.c:1859:3: note: in expansion of macro ‘SYSCALL_RET’
 1859 |   SYSCALL_RET(regs) = result;
      |   ^~~~~~~~~~~
seccomp_bpf.c: In function ‘get_syscall’:
seccomp_bpf.c:1795:1: warning: control reaches end of non-void function [-Wreturn-type]
 1795 | }
      | ^
make: *** [../lib.mk:140: /usr/src/linux-5.9.8/tools/testing/selftests/seccomp/seccomp_bpf] Error 1

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@...ian.org
`. `'   Freie Universitaet Berlin - glaubitz@...sik.fu-berlin.de
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