[Xenomai] [PATCH 3/3] lib/cobalt: wrap CXXABI One-time Constructor functions

Henning Schild henning.schild at siemens.com
Thu Mar 2 10:56:01 CET 2017


Am Wed, 25 Jan 2017 16:08:37 +0100
schrieb Henning Schild <henning.schild at siemens.com>:

> The implementation of these functions uses locks and has the potential
> to trigger a SIGXCPU when contended. Wrap them with assert_nrt so they
> reliably cause a switch when used in the rt context.
> 
> Signed-off-by: Henning Schild <henning.schild at siemens.com>
> ---
>  lib/cobalt/assert.wrappers  |  3 +++
>  lib/cobalt/assert_context.c | 19 +++++++++++++++++++
>  lib/cobalt/internal.h       | 12 ++++++++++++
>  lib/cobalt/wrappers.c       | 37
> +++++++++++++++++++++++++++++++++++++ 4 files changed, 71
> insertions(+)
> 
> diff --git a/lib/cobalt/assert.wrappers b/lib/cobalt/assert.wrappers
> index 7164858..65320ab 100644
> --- a/lib/cobalt/assert.wrappers
> +++ b/lib/cobalt/assert.wrappers
> @@ -1,2 +1,5 @@
>  --wrap malloc
>  --wrap free
> +--wrap __cxa_guard_acquire
> +--wrap __cxa_guard_release
> +--wrap __cxa_guard_abort
> diff --git a/lib/cobalt/assert_context.c b/lib/cobalt/assert_context.c
> index 2085953..fd18d6b 100644
> --- a/lib/cobalt/assert_context.c
> +++ b/lib/cobalt/assert_context.c
> @@ -66,3 +66,22 @@ COBALT_IMPL(void, free, (void *ptr))
>  	assert_nrt();
>  	__STD(free(ptr));
>  }
> +
> +/* CXXABI 3.3.2 One-time Construction API */
> +COBALT_IMPL(int, __cxa_guard_acquire, (__guard *g))
> +{
> +	assert_nrt();
> +	return __STD(__cxa_guard_acquire(g));
> +}
> +
> +COBALT_IMPL(void, __cxa_guard_release, (__guard *g))
> +{
> +	assert_nrt();
> +	__STD(__cxa_guard_release(g));
> +}
> +
> +COBALT_IMPL(void, __cxa_guard_abort, (__guard *g))
> +{
> +	assert_nrt();
> +	__STD(__cxa_guard_abort(g));
> +}
> diff --git a/lib/cobalt/internal.h b/lib/cobalt/internal.h
> index 1531901..8874f71 100644
> --- a/lib/cobalt/internal.h
> +++ b/lib/cobalt/internal.h
> @@ -93,4 +93,16 @@ extern int __cobalt_std_fifo_minpri,
>  extern int __cobalt_std_rr_minpri,
>  	   __cobalt_std_rr_maxpri;
>  
> +#ifdef __ARM_EABI__
> +typedef uint32_t __guard;
> +#else
> +typedef uint64_t __guard;
> +#endif
> +int __real___cxa_guard_acquire(__guard*);
> +void __real___cxa_guard_release(__guard*);
> +void __real___cxa_guard_abort(__guard*);
> +int __cxa_guard_acquire(__guard*);
> +void __cxa_guard_release(__guard*);
> +void __cxa_guard_abort(__guard*);
> +
>  #endif /* _LIB_COBALT_INTERNAL_H */
> diff --git a/lib/cobalt/wrappers.c b/lib/cobalt/wrappers.c
> index 43ca630..fa7fbcb 100644
> --- a/lib/cobalt/wrappers.c
> +++ b/lib/cobalt/wrappers.c
> @@ -43,6 +43,7 @@
>  #include <unistd.h>
>  #include <malloc.h>
>  #include <boilerplate/compiler.h>
> +#include <internal.h>
>  
>  /* sched */
>  __weak
> @@ -544,3 +545,39 @@ int __real_usleep(useconds_t usec)
>  {
>  	return usleep(usec);
>  }
> +
> +__weak
> +int __real___cxa_guard_acquire(__guard *g)
> +{
> +	return __cxa_guard_acquire(g);
> +}
> +
> +__weak
> +void __real___cxa_guard_release(__guard *g)
> +{
> +	return __cxa_guard_release(g);
> +}
> +
> +__weak
> +void __real___cxa_guard_abort(__guard *g)
> +{
> +	return __cxa_guard_abort(g);
> +}

The following weak symbols are not always replaced by the strong ones
from libstdc++. They are just here for C-code and can now break C++.

> +__weak
> +int __cxa_guard_acquire(__guard *g)
> +{
> +	return 0;
> +}
> +
> +__weak
> +void __cxa_guard_release(__guard *g)
> +{
> +	return;
> +}
> +
> +__weak
> +void __cxa_guard_abort(__guard *g)
> +{
> +	return;
> +}

For dynamically linked executables you do need "LD_DYNAMIC_WEAK" in
your env and for static linking "--whole-archive". Otherwise you might
end up using these weak dummies.

This patch introduced a critical bug! I will come up with a fix but
wanted to report the problem first.

Henning



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