[ECOS] Fedora Core 3 - Ecos synth crashes.

[John Carter <john.carter@tait.co.nz>]

I'm seeing a case on fedora core 3 where...
  * exactly the same executable whether built under fedora or built under debian (both built using the
    ecosV2.0 gnutools i386-elf-gcc)
  * seg faults under Fedora (on two different machines) (linux-2.6.9)
  * Works under debian unstable / Mandrake 9.1 / Mandrake 10 linux-2.4, 2.6.10&12

My current guess, following things around in the debugger is it is during 
running the __CTOR__ list, in particular setting up the sigactions.

Initially I thought it is due to a mismatch between the current linux
sigaction struct and the cyg_hal_sys_action struct. (Valgrind
certinaly suggested that this may be the case.) I tried fixing that
but it didn't resolve the problem.

My current best guess is things turn to custard when the SIGALRM's
start firing.

Looking ecos CVS I note 7 weeks ago Bart Veer was doing something in
relation with sigreturn so I wonder if it is worth back patching that,
and if so how much do I need? (Curiosly enough this all works under Linux 
2.6.12-rc3, 2.610  but not underfedora 2.6.9)


----------------------------------------------------------------------


Here is a description of the difference between the linux and the
cyg_hal_sys_sigaction structs....

http://ecos.sourceware.org/cgi-bin/cvsweb.cgi/ecos/packages/hal/synth/arch/current/include/hal_io.h?rev=1.13&content-type=text/x-cvsweb-markup&cvsroot=ecos
// The kernel sigaction structure has changed, to allow for >32
// signals. This is the old version, i.e. a struct old_sigaction, for
// use with the sigaction() system call rather than rt_sigaction(). It
// is preferred to the more modern version because gdb knows about
// rt_sigaction() and will start intercepting signals, but it seems to
// ignore sigaction().
struct cyg_hal_sys_sigaction {
     void        (*hal_handler)(int);
     long        hal_mask;
     int         hal_flags;
     void        (*hal_restorer)(void);
};

However, looking in /usr/include/bits/sigaction.h

struct sigaction
   {
     /* Signal handler.  */
#ifdef __USE_POSIX199309
     union
       {
 	/* Used if SA_SIGINFO is not set.  */
 	__sighandler_t sa_handler;
 	/* Used if SA_SIGINFO is set.  */
 	void (*sa_sigaction) (int, siginfo_t *, void *);
       }
     __sigaction_handler;
# define sa_handler	__sigaction_handler.sa_handler
# define sa_sigaction	__sigaction_handler.sa_sigaction
#else
     __sighandler_t sa_handler;
#endif

     /* Additional set of signals to be blocked.  */
     __sigset_t sa_mask;

     /* Special flags.  */
     int sa_flags;

     /* Restore handler.  */
     void (*sa_restorer) (void);
   };

Where, and this is the interesting bit...
/usr/include/bits/sigset.h says

# define _SIGSET_NWORDS	(1024 / (8 * sizeof (unsigned long int)))
typedef struct
   {
     unsigned long int __val[_SIGSET_NWORDS];
   } __sigset_t;


ie. Ecos thinks sa_mask is one int, linux thinks it's 32 int's in a
row. If a sigaction is near the edge of available VM a call to
sigaction crashes, otherwise it magically (sort of) works.





John Carter                             Phone : (64)(3) 358 6639
Tait Electronics                        Fax   : (64)(3) 359 4632
PO Box 1645 Christchurch                Email : john.carter@tait.co.nz
New Zealand


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