NAME

core − format of memory image file

SYNOPSIS

#include <sys/core.h>

DESCRIPTION

The operating system writes out a memory image of a terminated process when any of various errors occur.  See sigvec(2) for the list of reasons; the most common are memory violations, illegal instructions, bus errors, and user-generated quit signals.  The memory image is called core and is written in the process’s working directory (provided it can be; normal access controls apply).  Set-user-ID and set-group-ID programs do not produce core files when they terminate as this would cause a security loophole. 

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

The core file consists of a core structure, as defined in the <sys/core.h> file, followed by the data pages and then the stack pages of the process image.  The core structure includes the program’s header, the size of the text, data, and stack segments, the name of the program and the number of the signal that terminated the process.  The program’s header is described by the exec structure defined in the <sys/exec.h> file. 

struct core {
intc_magic;/∗ Corefile magic number ∗/
intc_len;/∗ Sizeof (struct core) ∗/
structregs c_regs; /∗ General purpose registers ∗/
struct exec c_aouthdr; /∗ A.out header ∗/
intc_signo;/∗ Killing signal, if any ∗/
intc_tsize;/∗ Text size (bytes) ∗/
intc_dsize;/∗ Data size (bytes) ∗/
intc_ssize;/∗ Stack size (bytes) ∗/
charc_cmdname[CORE_NAMELEN + 1]; /∗ Command name ∗/
structfpu c_fpu;/∗ external FPU state ∗/
intc_ucode;/∗ Exception no. from u_code ∗/
};

The members of the structure are:

c_magic The magic number CORE_MAGIC , as defined in <sys/core.h>. 

c_len The length of the core structure in the core file.  This need not be equal to the current size of a core structure as defined in <sys/core.h>, as the core file may have been produced on a different release of the OS/MP operating system. 

c_regs The general purpose registers at the time the core file was produced.  This structure is machine-dependent. 

c_aouthdr The executable image header of the program. 

c_signo The number of the signal that terminated the process; see sigvec(2). 

c_tsize The size of the text segment of the process at the time the core file was produced. 

c_dsize The size of the data segment of the process at the time the core file was produced.  This gives the amount of data space image in the core file. 

c_ssize The size of the stack segment of the process at the time the core file was produced.  This gives the amount of stack space image in the core file. 

c_cmdname The first CORE_NAMELEN characters of the last component of the path name of the program. 

c_fpu The status of the floating point hardware at the time the core file was produced. 

c_ucode The signal code of the signal that terminated the process, if any.  See sigvec(2). 

SEE ALSO

adb(1), dbx(1), getrlimit(2), sigvec(2)

Solbourne Computer, Inc.  —  18 February 1988