NAME    [Toc]    [Back]

     core - memory image file format

SYNOPSIS    [Toc]    [Back]

     #include <sys/param.h>
     #include <sys/core.h>

DESCRIPTION    [Toc]    [Back]

     A small number of signals which cause  abnormal  termination
of a process
     also  cause  a  record  of the process's in-core state to be
written to disk
     for later examination by one of the available debuggers (see
     sigaction(2)).  This memory image is written to a file named
     programname.core in the working directory, provided the terminated process
 had write permission in the directory, and provided the
abnormality
     did not cause a system crash.  (In this event, the  decision
to save the
     core file is arbitrary, see savecore(8).)

     The  maximum  size  of a programname.core file is limited by
setrlimit(2).
     Files which would be larger than the limit are not  created.

     The programname.core file consists of the u-area, whose size
(in pages)
     is defined by the UPAGES manifest in  the  <machine/param.h>
file.  The uarea
  starts with a user structure as given in <sys/user.h>.
The remainder
 of the programname.core file consists of the data  pages
followed by
     the  stack  pages  of the process image.  The amount of data
space image in
     the programname.core file is given (in pages) by  the  variable u_dsize in
     the  u-area.   The amount of stack image in the core file is
given (in
     pages) by the variable u_ssize in the u-area.  The size of a
``page'' is
     given    by    the    constant    PAGE_SIZE,    defined   in
<machine/param.h>.  The user
     structure is defined as:

           struct    user {
                struct    pcb u_pcb;

                struct    pstats u_stats;

                /*
                 * Remaining fields only  for  core  dump  and/or
ptrace--
                 * not valid at other times!
                 */
                struct    kinfo_proc u_kproc;
                struct    md_coredump u_md;
           };

     md_coredump is defined in the header file <machine/pcb.h>.

     The  on-disk  core  file  consists of a header followed by a
number of segments.
  Each segment is preceded by a coreseg structure giving the segment's
  type,  the virtual address where the bits resided in
process address
 space and the size of the segment.

     The core header specifies the lengths of the core header itself and each
     of  the  following core segment headers to allow for any machine dependent
     alignment requirements.

           struct coreseg {
                u_int32_t c_midmag;      /* magic, id, flags */
                u_long    c_addr;        /*  Virtual  address  of
segment */
                u_long     c_size;        /* Size of this segment
*/
           };

           struct core {
                u_int32_t c_midmag;      /* magic, id, flags */
                u_int16_t c_hdrsize;   /*  Size  of  this  header
(machdep algn) */
                u_int16_t  c_seghdrsize;   /*  Size  of a segment
header */
                u_int32_t c_nseg;        /* # of core segments */
                char    c_name[MAXCOMLEN+1];       /*   Copy   of
p->p_comm */
                u_int32_t c_signo;       /* Killing signal */
                u_long    c_ucode;       /* Hmm ? */
                u_long    c_cpusize;     /* Size of  machine  dependent segment */
                u_long     c_tsize;        /* Size of traditional
text segment */
                u_long    c_dsize;       /* Size  of  traditional
data segment */
                u_long     c_ssize;        /* Size of traditional
stack segment */
           };

     The core structure's c_midmag field is an a.out midmag  number with a
     COREMAGIC  magic  number  (see  a.out(5)) and flags from the
following list:

           #define CORE_CPU    1
           #define CORE_DATA   2
           #define CORE_STACK  4

SEE ALSO    [Toc]    [Back]

     gdb(1), pmdb(1), setrlimit(2), sigaction(2)

HISTORY    [Toc]    [Back]

     A core file format appeared in Version 3 AT&T UNIX.

OpenBSD     3.6                        December     11,      1993