siginfo(5) siginfo(5)
NAME
siginfo - signal generation information
SYNOPSIS
#include <siginfo.h>
DESCRIPTION
If a process is catching a signal, it may request information that
tells why the system generated that signal [see sigaction(2)]. If a
process is monitoring its children, it may receive information that
tells why a child changed state [see waitid(2)]. In either case, the
system returns the information in a structure of type siginfot,
which includes the following information:
int sisigno /* signal number */
int sierrno /* error number */
int sicode /* signal code */
int simachinexcep /* signal generated as
* a result of hardware exception */
sisigno contains the system-generated signal number. (For the
waitid(2) function, sisigno is always SIGCHLD.)
If sierrno is non-zero, it contains an error number associated with
this signal, as defined in errno.h.
sicode contains a code identifying the cause of the signal. If the
value of sicode is less than or equal to 0, then the signal was
generated by a user process [see kill(2) and sigsend(2)] and the
siginfo structure contains the following additional information:
pidt sipid /* sending process ID */
uidt siuid /* sending user ID */
Otherwise, sicode contains a signal-specific reason why the signal
was generated, as follows:
Signal Code Reason
__________________________________________________________
SIGILL ILLILLOPC illegal opcode
ILLPRVOPC privileged opcode
__________________________________________________________
SIGFPE FPEINTDIV integer divide by zero
FPEINTOVF integer overflow
FPEFLTDIV floating point divide by zero
FPEFLTOVF floating point overflow
FPEFLTUND floating point underflow
FPEFLTRES floating point inexact result
FPEFLTINV invalid floating point operation
FPEFLTSUB subscript out of range
FPEPRIVIO FP privilege violation
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siginfo(5) siginfo(5)
FPEUNIMPL FP unimplemented opcode
FPEFTLNAN FP NaN operand
__________________________________________________________
SIGSEGV SEGVCODE code access
SEGVDATA data access
__________________________________________________________
SIGBUS BUSALIGN misaligned data access
BUSPROT protection violation
__________________________________________________________
SIGTRAP TRAPBRKPT process breakpoint
TRAPTRACE process trace trap
__________________________________________________________
SIGCHLD CLDEXITED child has exited
CLDKILLED child was killed
CLDDUMPED child terminated abnormally
CLDTRAPPED traced child has trapped
CLDSTOPPED child has stopped
CLDCONTINUED stopped child had continued
__________________________________________________________
SIGPOLL POLLIN data input available
POLLOUT output buffers available
POLLMSG input message available
POLLERR I/O error
POLLPRI high priority input available
POLLHUP device disconnected
In addition, the following signal-dependent information is available
for kernel-generated signals:
Signal Field Value
______________________________________________________________
SIGCHLD pidt sipid child process ID
int sistatus exit value or signal
______________________________________________________________
SIGPOLL long siband band event for POLLIN, POLLOUT, or
POLLMSG
NOTES
For SIGCHLD signals, if sicode is equal to CLDEXITED, then
sistatus is equal to the exit value of the process; otherwise, it is
equal to the signal that caused the process to change state. If
simachinexcep is non zero, the signal was generated as a result of a
machine exception. The signals that an exception may give rise to
are SIGSEGV, SIGILL, SIGBUS, SIGTRAP and SIGFPE. When one of these
signals delivered as a result of a machine exception, one or more
exception blocks containing relevant information is also made
available through the siginfo structure. sincodes contains the
number of exception blocks available, and siexblks points to an
array of exception blocks containing sincodes elements. The
contents of an exception block are the signal number, ebsigno (the
same as sisigno), the exception code, ebcode (one of those listed
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siginfo(5) siginfo(5)
above), and signal-specific information, ebregisters. ebregister
contains valid information only for SIGSEGV, SIGBUS and SIGFPE.
For SIGSEGV and SIGBUS, the address, transaction and data registers
of the faulting data-pipe stage are available in ebdma, ebdmt and
ebdmd, respectively.
For SIGFPE imprecise exception codes, the high and low words of the
floating point result are available in ebfprh and ebfprl, and the
floating point imprecise operation type register is available in
ebfpit.
SEE ALSO
sigaction(2), waitid(2), signal(5).
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