linux-kernel - Re: [PATCH] samples/seccomp/Makefile: Do not build tests if cross-compiling for MIPS

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Date:	Thu, 13 Feb 2014 17:30:25 +0000
From:	Markos Chandras <Markos.Chandras@...tec.com>
To:	<linux-mips@...ux-mips.org>
CC:	<linux-next@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] samples/seccomp/Makefile: Do not build tests if cross-compiling
 for MIPS

On 02/13/2014 05:27 PM, Markos Chandras wrote:
> The Makefile is designed to use the host toolchain so it may be
> unsafe to build the tests if the kernel has been configured and built
> for another architecture. This fixes a build problem when the kernel has
> been configured and built for the MIPS architecture but the host is
> not MIPS (cross-compiled). The MIPS syscalls are only defined
> if one of the following is true:
>
> 1) _MIPS_SIM == _MIPS_SIM_ABI64
> 2) _MIPS_SIM == _MIPS_SIM_ABI32
> 3) _MIPS_SIM == _MIPS_SIM_NABI32
>
> Of course, none of these make sense on a non-MIPS toolchain and the
> following build problem occurs when building on a non-MIPS host.
>
> linux/usr/include/linux/kexec.h:50:
> userspace cannot reference function or variable defined in the kernel
> samples/seccomp/bpf-direct.c: In function ‘emulator’:
> samples/seccomp/bpf-direct.c:76:17: error:
> ‘__NR_write’ undeclared (first use in this function)
>
> Cc: linux-next@...r.kernel.org
> Cc: linux-kernel@...ux-mips.org
> Reported-by: Paul Gortmaker <paul.gortmaker@...driver.com>
> Signed-off-by: Markos Chandras <markos.chandras@...tec.com>
> ---
> This problem is only reproducible on the linux-next tree at the moment
> ---
>   samples/seccomp/Makefile | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/samples/seccomp/Makefile b/samples/seccomp/Makefile
> index 7203e66..f6bda1c 100644
> --- a/samples/seccomp/Makefile
> +++ b/samples/seccomp/Makefile
> @@ -17,9 +17,14 @@ HOSTCFLAGS_bpf-direct.o += -I$(objtree)/usr/include
>   HOSTCFLAGS_bpf-direct.o += -idirafter $(objtree)/include
>   bpf-direct-objs := bpf-direct.o
>
> +# MIPS system calls are defined based on the -mabi that is passed
> +# to the toolchain which may or may not be a valid option
> +# for the host toolchain. So disable tests if target architecture
> +# is mips but the host isn't.
> +ifndef CONFIG_MIPS
>   # Try to match the kernel target.
> -ifndef CONFIG_64BIT
>   ifndef CROSS_COMPILE
> +ifndef CONFIG_64BIT
>
>   # s390 has -m31 flag to build 31 bit binaries
>   ifndef CONFIG_S390
> @@ -40,3 +45,4 @@ endif
>
>   # Tell kbuild to always build the programs
>   always := $(hostprogs-y)
> +endif
>

CC'ing the correct linux-kernel address. Sorry about that.

-- 
markos

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