SIGALTSTACK(2) Linux Programmer's Manual SIGALTSTACK(2)
sigaltstack - get or set alternate signal stack content
int sigaltstack(const stack_t *ss, stack_t *oss);
ss points to a signalstack structure defined in <signal.h> contain-
ing stack content after the call.
oss if not NULL, points to a signalstack structure containing stack
content before the call.
sigaction(2) may indicate that a signal should execute on an alternate
stack. Where this is the case, sigaltstack(2) stores the signal in an
alternate stack structure ss where its execution status may be examined
prior to processing.
The sigaltstack struct is defined in <signal.h> as follows:
void *ss_sp /* SVID3 uses caddr_t ss_sp
ss_sp points to the stack structure.
specifies the stack state to SS_DISABLE or SS_ONSTACK as fol-
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
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 execution 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.
sigaltstack(2) returns 0 on success and -1 on failure.
sigaltstack(2) sets errno for the following conditions:
EINVAL ss is not a null pointer the ss_flags member pointed to by ss
contains flags other than SS_DISABLE.
ENOMEM The size of the alternate stack area is less than MINSIGSTKSZ.
EPERM An attempt was made to modify an active stack.
This function comforms to: XPG4-UNIX.
getcontext(2), sigaction(2), sigsetjmp(3).
Red Hat Linux 6.1 20 September 1999 SIGALTSTACK(2)