sigaltstack(2)sigaltstack(2)NAMEsigaltstack - set or get signal alternate stack context
SYNOPSIS
#include <signal.h>
int sigaltstack(
const stack_t *ss,
stack_t *oss );
The following function declaration does not conform to current stan‐
dards and is supported only for backward compatibility: #include <sig‐
nal.h>
int sigaltstack(
stack_t *ss,
stack_t *oss );
STANDARDS
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
sigaltstack(): XPG4-UNIX
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
PARAMETERS
If valid, specifies a pointer to a structure that indicates what will
be in effect upon return from the call to the sigaltstack function. If
not NULL, specifies the pointer to a structure that contains the alter‐
nate signal stack that was in effect prior to the call to the sigalt‐
stack function.
DESCRIPTION
This function enables another stack area to be defined where signals
can be examined for their execution status and processed. If a signal's
action, specified by the sigaction(2) function, indicates that a signal
should execute on an alternate stack, that signal is examined for its
processing status. A process that is not currently executing on the
signal stack is switched to an alternate stack for the duration of the
handler's execution.
The sigaltstack structure is set up as follows:
void *ss_sp /* SVID3 uses caddr_t ss_sp int ss_flags
size_t ss_size
The values for the fields are: Signal stack pointer. Specifies the new
stack state and may be set to either SS_DISABLE or SS_ONSTACK as fol‐
lows: If ss is not NULL, the new state may be set to SS_DISABLE, which
specifies that the stack is to be disabled and ss_sp and ss_size are
ignored. If SS_DISABLE is not set, the stack will be enabled. If oss
is not NULL, the stack state may be either SS_ONSTACK or SS_DISABLE.
The value SS_ONSTACK indicates that the process is currently executing
on the alternate stack and that any attempt to modify it during execu‐
tion will fail. The value SS_DISABLE indicates that the current signal
stack is disabled. Specifies the size of the stack.
The value SIGSTKSZ defines the average number of bytes used when allo‐
cating an alternate stack area. The value MINSIGSTKSZ defines the min‐
imum stack size for a signal handler. When processing an alternate
stack size, your program should include these values in the stack
requirement to plan for the overhead of the operating system.
RETURN VALUES
Upon successful completion, zero (0) is returned. On error, the value
-1 is returned and errno is set to indicate the error.
ERRORS
The sigaltstack() function sets errno to the specified values for the
following conditions: The ss parameter is not a null pointer, and the
ss_flags member pointed to by ss contains flags other than SS_DISABLE.
The size of the alternate stack area is less than MINSIGSTKSZ. An
attempt was made to modify an active stack.
SEE ALSO
Functions: getcontext(2), sigaction(2)
Routines: sigsetjmp(3)
Files: ucontext(5)
Standards: standards(5)sigaltstack(2)
