Rewrite description of core dump format to reflect reality.
Addresses PR#11145 by me.
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nathanw
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@ -1,4 +1,4 @@
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.\" $NetBSD: core.5,v 1.11 1999/10/10 15:17:43 jdolecek Exp $
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.\" $NetBSD: core.5,v 1.12 2000/10/07 17:45:26 nathanw Exp $
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.\"
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.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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@ -33,7 +33,7 @@
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.\"
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.\" @(#)core.5 8.3 (Berkeley) 12/11/93
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.\"
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.Dd December 11, 1993
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.Dd October 7, 2000
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.Dt CORE 5
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.Os
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.Sh NAME
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@ -89,34 +89,114 @@ The maximum size of a core file is limited by
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.Xr setrlimit 2 .
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Files which would be larger than the limit are not created.
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.Pp
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The core file consists of the
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.Fa u. area ,
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whose size (in pages) is defined by the
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.Dv UPAGES
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manifest in the
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.Aq Pa sys/param.h
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file. The
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.Fa u. area
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starts with a
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.Fa user
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structure as given in
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.Aq Pa sys/user.h .
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The remainder of the core file consists of the data pages followed by
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the stack pages of the process image.
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The amount of data space image in the core file is given (in pages) by the
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variable
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.Fa u_dsize
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in the
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.Fa u. area .
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The amount of stack image in the core file is given (in pages) by the
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variable
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.Fa u_ssize
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in the
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.Fa u. area .
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The size of a ``page'' is given by the constant
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.Dv NBPG
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(also from
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.Aq Pa sys/param.h ) .
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The core file contains of a core header followed by a number of
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segments. Each segment is preceded by a core segment header.
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Both the core header and core segment header are defined in
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.Aq Pa sys/core.h .
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The core header,
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.Fa struct core ,
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specifies the lengths of the core header itself and
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each of the following core segment headers to allow for any machine
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dependent alignment requirements.
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.Bd -literal
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struct core {
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u_int32_t c_midmag; /* magic, id, flags */
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u_int16_t c_hdrsize; /* Size of this header (machdep algn) */
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u_int16_t c_seghdrsize; /* Size of a segment header */
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u_int32_t c_nseg; /* # of core segments */
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char c_name[MAXCOMLEN+1]; /* Copy of p->p_comm */
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u_int32_t c_signo; /* Killing signal */
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u_long c_ucode; /* Signal code */
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u_long c_cpusize; /* Size of machine dependent segment */
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u_long c_tsize; /* Size of traditional text segment */
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u_long c_dsize; /* Size of traditional data segment */
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u_long c_ssize; /* Size of traditional stack segment */
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};
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.Ed
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.Pp
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The fields of
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.Fa struct core
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are as follows:
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.Bl -tag -width XXXc_seghdrsize
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.It c_midmag
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Core file machine ID, magic value, and flags.
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These values may be extracted with the
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.Fn CORE_GETMID ,
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.Fn CORE_GETMAGIC ,
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and
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.Fn CORE_GETFLAG
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macros. The machine ID values are listed in
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.Aq Pa sys/exec_aout.h .
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For a valid core file, the magic value in the header must be
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.Dv COREMAGIC .
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No flags are defined for the core header.
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.It c_hdrsize
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Size of this data structure.
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.It c_seghdrsize
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Size of a segment header.
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.It c_nseg
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Number of segments that follow this header.
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.It c_name
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Process name, copied from the p_comm field of
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.Fa struct proc .
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.It c_signo
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Signal that caused the process to dump core.
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.It c_ucode
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Code associated with the signal.
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.It c_cpusize
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Size of the segment containing CPU-specific information.
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This segment will have the
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.Dv CORE_CPU
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flag set.
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.It c_tsize
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Size of the segment containing the program text.
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.It c_dsize
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Size of the segment containing the program's traditional data area.
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.It c_ssize
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Size of the segment containing the program's traditional stack area.
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This segment will have the
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.Dv CORE_STACK
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flag set.
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.El
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The header is followed by
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.Fa c_nseg
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segments, each of which is preceded with a segment header,
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.Fa struct coreseg :
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.Bd -literal
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struct coreseg {
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u_int32_t c_midmag; /* magic, id, flags */
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u_long c_addr; /* Virtual address of segment */
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u_long c_size; /* Size of this segment */
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};
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.Ed
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.Pp
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The fields of
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.Fa struct coreseg
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are as follows:
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.Bl -tag -width XXXc_midmag
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.It c_midmag
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Core segment magic value and flags.
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These values may be extracted with the
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.Fn CORE_GETMAGIC
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and
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.Fn CORE_GETFLAG
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macros.
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The magic value in the segment header must be
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.Dv CORESEGMAGIC .
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Exactly one of of the flags
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.Dv CORE_CPU ,
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.Dv CORE_DATA,
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or
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.Dv CORE_STACK
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will be set to indicate the segment type.
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.It c_addr
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Virtual address of the segment in the program image.
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Meaningless if the segment type is
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.Dv CORE_CPU .
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.It c_size
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Size of the segment, not including this header.
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.El
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.Sh SEE ALSO
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.Xr gdb 1 ,
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.Xr setrlimit 2 ,
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@ -128,3 +208,8 @@ A
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.Nm core
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file format appeared in
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.At v6 .
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.Sh BUGS
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There is no standard location or name for the
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CPU-dependant data structure stored in the
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.Dv CORE_CPU
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segment.
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