sigaltstack - set or get signal alternate stack context
#include <signal.h>
int sigaltstack(
const stack_t *ss,
stack_t *oss );
The following function declaration does not conform to
current standards and is supported only for backward compatibility:
#include <signal.h>
int sigaltstack(
stack_t *ss,
stack_t *oss );
Interfaces documented on this reference page conform to
industry standards as follows:
sigaltstack(): XPG4-UNIX
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
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 alternate signal
stack that was in effect prior to the call to the sigaltstack
function.
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 follows: 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
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 allocating an alternate stack area. The value
MINSIGSTKSZ defines the minimum 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.
Upon successful completion, zero (0) is returned. On
error, the value -1 is returned and errno is set to indicate
the error.
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.
Functions: getcontext(2), sigaction(2)
Routines: sigsetjmp(3)
Files: ucontext(5)
Standards: standards(5)
sigaltstack(2)
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