stack_violation(3c) [sunos man page]
stack_violation(3C) Standard C Library Functions stack_violation(3C) NAME
stack_violation - determine stack boundary violation event SYNOPSIS
#include <ucontext.h> int stack_violation(int sig, const siginfo_t *sip, const ucontext_t *ucp); DESCRIPTION
The stack_violation() function returns a boolean value indicating whether the signal, sig, and accompanying signal information, sip, and saved context, ucp, represent a stack boundary violation event or a stack overflow. RETURN VALUES
The stack_violation() function returns 0 if the signal does not represent a stack boundary violation event and 1 if the signal does repre- sent a stack boundary violation event. ERRORS
No errors are defined. EXAMPLES
Example 1: Set up a signal handler to run on an alternate stack. The following example sets up a signal handler for SIGSEGV to run on an alternate signal stack. For each signal it handles, the handler emits a message to indicate if the signal was produced due to a stack boundary violation. #include <stdlib.h> #include <unistd.h> #include <ucontext.h> #include <signal.h> static void handler(int sig, siginfo_t *sip, void *p) { ucontext_t *ucp = p; const char *str; if (stack_violation(sig, sip, ucp)) str = "stack violation. "; else str = "no stack violation. "; (void) write(STDERR_FILENO, str, strlen(str)); exit(1); } int main(int argc, char **argv) { struct sigaction sa; stack_t altstack; altstack.ss_size = SIGSTKSZ; altstack.ss_sp = malloc(SIGSTKSZ); altstack.ss_flags = 0; (void) sigaltstack(&altstack, NULL); sa.sa_sigaction = handler; (void) sigfillset(&sa.sa_mask); sa.sa_flags = SA_ONSTACK | SA_SIGINFO; (void) sigaction(SIGSEGV, &sa, NULL); /* * The application is now set up to use stack_violation(3C). */ return(0); } USAGE
An application typically uses stack_violation() in a signal handler that has been installed for SIGSEGV using sigaction(2) with the SA_SIG- INFO flag set and is configured to run on an alternate signal stack. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Evolving | +-----------------------------+-----------------------------+ |MT-Level |Async-Signal-Safe | +-----------------------------+-----------------------------+ SEE ALSO
sigaction(2), sigaltstack(2), stack_getbounds(3C), stack_inbounds(3C), stack_setbounds(3C), attributes(5) SunOS 5.10 18 Jul 2002 stack_violation(3C)
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sigaltstack(2) System Calls sigaltstack(2) NAME
sigaltstack - set or get signal alternate stack context SYNOPSIS
#include <signal.h> int sigaltstack(const stack_t *restrict ss, stack_t *restrict oss); DESCRIPTION
The sigaltstack() function allows a thread to define and examine the state of an alternate stack area on which signals are processed. If ss is non-zero, it specifies a pointer to and the size of a stack area on which to deliver signals, and informs the system whether the thread is currently executing on that stack. When a signal's action indicates its handler should execute on the alternate signal stack (speci- fied with a sigaction(2) call), the system checks whether the thread chosen to execute the signal handler is currently executing on that stack. If the thread is not currently executing on the signal stack, the system arranges a switch to the alternate signal stack for the duration of the signal handler's execution. The stack_t structure includes the following members: int *ss_sp long ss_size int ss_flags If ss is not NULL, it points to a structure specifying the alternate signal stack that will take effect upon successful return from sigalt- stack(). The ss_sp and ss_size members specify the new base and size of the stack, which is automatically adjusted for direction of growth and alignment. The ss_flags member specifies the new stack state and may be set to the following: SS_DISABLE 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, it points to a structure specifying the alternate signal stack that was in effect prior to the call to sigaltstack(). The ss_sp and ss_size members specify the base and size of that stack. The ss_flags member specifies the stack's state, and may contain the following values: SS_ONSTACK The thread is currently executing on the alternate signal stack. Attempts to modify the alternate signal stack while the thread is executing on it will fail. SS_DISABLE The alternate signal stack is currently disabled. RETURN VALUES
Upon successful completion, 0 is return. Otherwise, -1 is returned and errno is set to indicate the error. ERRORS
The sigaltstack() function will fail if: EFAULT The ss or oss argument points to an illegal address. EINVAL The ss argument is not a null pointer, and 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. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |Async-Signal-Safe | +-----------------------------+-----------------------------+ SEE ALSO
getcontext(2), mmap(2), sigaction(2), ucontext.h(3HEAD), attributes(5), standards(5) NOTES
The value SIGSTKSZ is defined to be the number of bytes that would be used to cover the usual case when allocating an alternate stack area. The value MINSIGSTKSZ is defined to be the minimum stack size for a signal handler. In computing an alternate stack size, a program should add that amount to its stack requirements to allow for the operating system overhead. The following code fragment is typically used to allocate an alternate stack with an adjacent red zone (an unmapped page) to guard against stack overflow, as with default stacks: #include <signal.h> #include <sys/mman.h> stack_t sigstk; sigstk.ss_sp = mmap(NULL, SIGSTKSZ, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); if (sigstk.ss_sp == MAP_FAILED) /* error return */; sigstk.ss_size = SIGSTKSZ; sigstk.ss_flags = 0; if (sigaltstack(&sigstk, NULL) < 0) perror("sigaltstack"); SunOS 5.11 1 Nov 2003 sigaltstack(2)