core(4) manual page
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core - core image file
The operating system writes out
a core image of a process when it is terminated due to the receipt of some
signals. The core image is called core and is written in the process’s working
directory (provided it can be; normal access controls apply). A process
with an effective user ID
different from the real user ID
will not produce
a core image.
The core file contains all the process information pertinent
to debugging: contents of hardware registers, process status and process
data. The format of a core file is object file specific.
For ELF
executable
programs (see a.out(4)
), the core file generated is also an ELF
file, containing
ELF
program and file headers. The e_type field in the file header has type
ET_CORE
. The program header contains an entry for every loadable and writable
segment that was part of the process address space, including shared library
segments. The contents of the segments themselves are also part of the
core image.
The program header of an ELF
core file also contains a NOTE
segment. This segment may contain the following entries. Each has entry
name "CORE"
and presents the contents of a system structure:
- prstatus_t
- The entry containing this structure has a NOTE
type of 1. This structure
contains things of interest to a debugger from the operating system’s u-area,
such as the general registers, signal dispositions, state, reason for stopping,
process ID and so forth. The prstatus_t structure is defined in <sys/procfs.h>.
- prfpregset_t
- This entry is present only if the process used the floating-point
hardware. It has a NOTE
type of 2 and contains the floating-point registers.
The prfpregset_t structure is defined in <sys/procfs.h>.
- prpsinfo_t
- The entry
containing this structure has a NOTE
type of 3. It contains information
of interest to the ps(1)
command, such as process status, cpu usage, "nice"
value, controlling terminal, user ID, process ID, the name of the executable
and so forth. The prpsinfo_t structure is defined in <sys/procfs.h>.
- prxregset_t
- This entry is present only if the process has extra register state associated
with it. It has a NOTE
type of 4 and contains the extra register state.
The prxregset_t structure is defined in <sys/procfs.h>.
- char *
- The entry containing
this structure has a NOTE
type of 5 and contains a string describing
the specific model of the hardware platform on which this core file was
created. This information is the same as provided by sysinfo(2)
when invoked
with the command SI_PLATFORM
.
- auxv_t array
- The entry containing this structure
has a NOTE
type of 6. It contains values of entries in the auxiliary vector
that is passed by the operating system as startup information to the dynamic
linker. Auxiliary vector information is defined in <sys/auxv.h>.
The size of
the core file created by a process may be controlled by the user (see getrlimit(2)
).
adb(1)
, gcore(1)
, ps(1)
, crash(1M)
, getrlimit(2)
, setuid(2)
, sysinfo(2)
,
elf(3E)
, a.out(4)
, proc(4)
, signal(5)
ANSI C Programmer’s Guide
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