CORE(5)                   NetBSD File Formats Manual                   CORE(5)

NAME
     core -- memory image file format

SYNOPSIS
     #include <sys/param.h>

     For a.out-format core files:

     #include <sys/core.h>

     For ELF-format core files:

     #include <sys/exec.h>
     #include <sys/exec_elf.h>

DESCRIPTION
     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 signal(7)).

     This memory image is written to a file named from a per-process template;
     provided the terminated process had write permission, 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 file is named
     from a per-process template, mapped to the sysctl variable
     proc.<pid>.corename (where <pid> has to be replaced by the pid in decimal
     format of the process).  This template is either an absolute or relative
     path name, in which format characters can be used, preceded by the per-
     cent character (``%'').  The following characters are recognized as for-
     mat and substituted:
           n     The process's name
           p     The PID of the process (in decimal)
           t     The process's creation date (a la time(3), in decimal)
           u     The login name, as returned by getlogin(2)

     By default, the per-process template string points to the default core
     name template, which is mapped to the sysctl variable kern.defcorename.
     Changing this value on a live system will change the core name template
     for all processes which didn't have a per-process template set.  The
     default value of the default core name template is %n.core and can be
     changed at compile-time with the kernel configuration option options
     DEFCORENAME (see options(4))

     The per-process template string is inherited on process creation, but is
     reset to point to the default core name template on execution of a set-id
     binary.

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

   ELF CORE FORMAT
     ELF-format core files are described by a standard ELF exec header and a
     series of ELF program headers.  Each program header describes a range of
     the virtual address space of the process.

     In addition, NetBSD ELF core files include an ELF note section which pro-
     vides additional information about the process.  The first note in the
     note section has a note name of ``NetBSD-CORE'' and a note type of
     ELF_NOTE_NETBSD_CORE_PROCINFO (1), and contains the following structure:

     struct netbsd_elfcore_procinfo {
        /* Version 1 fields start here. */
         uint32_t cpi_version;      /* netbsd_elfcore_procinfo version */
         uint32_t cpi_cpisize;      /* sizeof(netbsd_elfcore_procinfo) */
         uint32_t cpi_signo;        /* killing signal */
         uint32_t cpi_sigcode;      /* signal code */
         uint32_t cpi_sigpend[4];   /* pending signals */
         uint32_t cpi_sigmask[4];   /* blocked signals */
         uint32_t cpi_sigignore[4]; /* blocked signals */
         uint32_t cpi_sigcatch[4];  /* blocked signals */
         int32_t  cpi_pid;          /* process ID */
         int32_t  cpi_ppid;         /* parent process ID */
         int32_t  cpi_pgrp;         /* process group ID */
         int32_t  cpi_sid;          /* session ID */
         uint32_t cpi_ruid;         /* real user ID */
         uint32_t cpi_euid;         /* effective user ID */
         uint32_t cpi_svuid;        /* saved user ID */
         uint32_t cpi_rgid;         /* real group ID */
         uint32_t cpi_egid;         /* effective group ID */
         uint32_t cpi_svgid;        /* saved group ID */
         uint32_t cpi_nlwps;        /* number of LWPs */
         int8_t   cpi_name[32];     /* copy of p->p_comm */
         /* Add version 2 fields below here. */
     };

     The fields of struct netbsd_elfcore_procinfo are as follows:

     cpi_version      The version of this structure.  The current version is
                      defined by the NETBSD_ELFCORE_PROCINFO_VERSION constant.

     cpi_cpisize      The size of this structure.

     cpi_signo        Signal that caused the process to dump core.

     cpi_sigcode      Signal-specific code, if any, corresponding to
                      cpi_signo.

     cpi_sigpend      A mask of signals pending delivery to the process.  This
                      may be examined by copying it to a sigset_t.

     cpi_sigmask      The set of signals currently blocked by the process.
                      This may be examined by copying it to a sigset_t.

     cpi_sigignore    The set of signals currently being ignored by the
                      process.  This may be examined by copying it to a
                      sigset_t.

     cpi_sigcatch     The set of signals with registers signals handlers for
                      the process.  This may be examined by copying it to a
                      sigset_t.

     cpi_pid          Process ID of the process.

     cpi_ppid         Process ID of the parent process.

     cpi_pgrp         Process group ID of the process.

     cpi_sid          Session ID of the process.

     cpi_ruid         Real user ID of the process.

     cpi_euid         Effective user ID of the process.

     cpi_svuid        Saved user ID of the process.

     cpi_rgid         Real group ID of the process.

     cpi_egid         Effective group ID of the process.

     cpi_svgid        Saved group ID of the process.

     cpi_nlwps        Number of kernel-visible execution contexts (LWPs) of
                      the process.

     cpi_name         Process name, copied from the p_comm field of struct
                      proc.

     The note section also contains additional notes for each kernel-visible
     execution context of the process (LWP).  These notes have names of the
     form ``NetBSD-CORE@nn'' where ``nn'' is the LWP ID of the execution con-
     text, for example: ``NetBSD-CORE@1''.  These notes contain register and
     other per-execution context data in the same format as is used by the
     ptrace(2) system call.  The note types correspond to the ptrace(2)
     request numbers that return the same data.  For example, a note with a
     note type of PT_GETREGS would contain a struct reg with the register con-
     tents of the execution context.  For a complete list of available
     ptrace(2) request types for a given architecture, refer to that architec-
     ture's <machine/ptrace.h> header file.

   A.OUT CORE FORMAT
     The core file consists of a core header followed by a number of segments.
     Each segment is preceded by a core segment header.  Both the core header
     and core segment header are defined in <sys/core.h>.

     The core header, struct core, 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 core {
         uint32_t c_midmag;         /* magic, id, flags */
         uint16_t c_hdrsize;        /* Size of this header (machdep algn) */
         uint16_t c_seghdrsize;     /* Size of a segment header */
         uint32_t c_nseg;           /* # of core segments */
         char      c_name[MAXCOMLEN+1];      /* Copy of p->p_comm */
         uint32_t c_signo;          /* Killing signal */
         u_long    c_ucode;          /* Signal code */
         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 fields of struct core are as follows:

     c_midmag         Core file machine ID, magic value, and flags.  These
                      values may be extracted with the CORE_GETMID(),
                      CORE_GETMAGIC(), and CORE_GETFLAG() macros. The machine
                      ID values are listed in <sys/exec_aout.h>.  For a valid
                      core file, the magic value in the header must be
                      COREMAGIC.  No flags are defined for the core header.

     c_hdrsize        Size of this data structure.

     c_seghdrsize     Size of a segment header.

     c_nseg           Number of segments that follow this header.

     c_name           Process name, copied from the p_comm field of struct
                      proc.

     c_signo          Signal that caused the process to dump core.

     c_ucode          Code associated with the signal.

     c_cpusize        Size of the segment containing CPU-specific information.
                      This segment will have the CORE_CPU flag set.

     c_tsize          Size of the segment containing the program text.

     c_dsize          Size of the segment containing the program's traditional
                      data area.

     c_ssize          Size of the segment containing the program's traditional
                      stack area.  This segment will have the CORE_STACK flag
                      set.
     The header is followed by c_nseg segments, each of which is preceded with
     a segment header, struct coreseg:

     struct coreseg {
        uint32_t c_midmag;  /* magic, id, flags */
        u_long    c_addr;    /* Virtual address of segment */
        u_long    c_size;    /* Size of this segment */
     };

     The fields of struct coreseg are as follows:

     c_midmag     Core segment magic value and flags.  These values may be
                  extracted with the CORE_GETMAGIC() and CORE_GETFLAG()
                  macros.  The magic value in the segment header must be
                  CORESEGMAGIC.  Exactly one of the flags CORE_CPU, CORE_DATA,
                  or CORE_STACK will be set to indicate the segment type.

     c_addr       Virtual address of the segment in the program image.  Mean-
                  ingless if the segment type is CORE_CPU.

     c_size       Size of the segment, not including this header.

SEE ALSO
     a.out(5), elf(5), gdb(1), setrlimit(2), sysctl(3), signal(7), sysctl(8)

HISTORY
     A core file format appeared in Version 6 AT&T UNIX.  The NetBSD a.out
     core file format was introduced in NetBSD 1.0.  The NetBSD ELF core file
     format was introduced in NetBSD 1.6.

     In releases previous to NetBSD 1.6, ELF program images produced a.out-
     format core files.

BUGS
     There is no standard location or name for the CPU-dependent data struc-
     ture stored in the CORE_CPU segment.

NetBSD 5.0.1                     July 8, 2002                     NetBSD 5.0.1

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