Re: [Xenomai-core] [PATCH 2/2] rtdk: Add assert_context helpers

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Jan Kiszka wrote:
> Provide assert_nrt helper that checks if the caller is either not a
> shadow thread or is currently running in relaxed mode. If not, SIG_XCPU
> is raised.
> 
> This service is then used to provide wrappers for glibc functions that
> are not realtime-safe but do not always trigger a syscall. Such
> functions may therefore be used by RT threads in primary mode for quite
> a while without being detected via some Xenomai mode switch. Moreover,
> some functions that go through the vsyscall page even to raise an
> ordinary syscall may not allow proper stack backtraces, making it harder
> to find their callers.
> 
> So far we provide wrappers (for use with the --wrap linker switch) for
> malloc/free, gettimeofday and clock_gettime. Adding more (if there
> are/will be more) is trivial.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@domain.hid>
> ---
> 
>  src/rtdk/Makefile.am      |    5 +-
>  src/rtdk/assert_context.c |   97 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 100 insertions(+), 2 deletions(-)
>  create mode 100644 src/rtdk/assert_context.c
> 
> diff --git a/src/rtdk/Makefile.am b/src/rtdk/Makefile.am
> index cb80262..5b76b5d 100644
> --- a/src/rtdk/Makefile.am
> +++ b/src/rtdk/Makefile.am
> @@ -1,10 +1,11 @@
>  lib_LTLIBRARIES = librtdk.la
>  
> -librtdk_la_LDFLAGS = -version-info 0:0:0 -lpthread
> +librtdk_la_LDFLAGS = -version-info 0:0:0 -lpthread -lrt
>  
>  librtdk_la_SOURCES = \
>  	init.c \
> -	rt_print.c
> +	rt_print.c \
> +	assert_context.c
>  
>  librtdk_la_CPPFLAGS = \
>  	@XENO_USER_CFLAGS@ \
> diff --git a/src/rtdk/assert_context.c b/src/rtdk/assert_context.c
> new file mode 100644
> index 0000000..e01fc93
> --- /dev/null
> +++ b/src/rtdk/assert_context.c
> @@ -0,0 +1,97 @@
> +/*
> + * Copyright (C) 2008 Jan Kiszka <jan.kiszka@domain.hid>.
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> +
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, write to the Free Software
> + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
> + */
> +
> +#include <signal.h>
> +#include <stdlib.h>
> +#include <time.h>
> +#include <sys/time.h>
> +
> +#include <nucleus/thread.h>
> +#include <asm-generic/syscall.h>
> +#include <asm-generic/bits/current.h>
> +
> +void assert_nrt(void)
> +{
> +	xnthread_info_t info;
> +	int err;
> +
> +	if (unlikely(xeno_get_current() != XN_NO_HANDLE &&
> +		     !(xeno_get_current_mode() & XNRELAX))) {
> +
> +		err = XENOMAI_SYSCALL1(__xn_sys_current_info, &info);
> +
> +		if (err) {
> +			fprintf(stderr, "__xn_sys_current_info failed: %s\n",
> +				strerror(-err));
> +			return;
> +		}
> +
> +		if (info.state & XNTRAPSW)
> +			pthread_kill(pthread_self(), SIGXCPU);
> +	}
> +}
> +
> +/* Memory allocation services */
> +__attribute__ ((weak))
> +void *__real_malloc(size_t size)
> +{
> +	return malloc(size);
> +}
> +
> +void *__warp_malloc(size_t size)
> +{
> +	assert_nrt();
> +	return __real_malloc(size);
> +}

It is wrap not warp, and the __real functions should not be put in the
same compilation unit as the __wrap functions.

-- 
                                                 Gilles.