/**
* slibc — Yet another C library
* Copyright © 2015, 2016 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <slibc/internals.h>
#include <alloca.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
/**
* Unless the stack can grow with `n` bytes
* without overflowing, the program shall
* either be killed by the kernel (SIGSEGV)
* or this function shall indicate that the
* stack cannot be grown.
*
* @param n The number of bytes the stack must be able to grow.
* @return 0 if the stack can grow, 1 otherwise.
*/
int stack_will_overflow(intptr_t n)
{
void* prev_brk;
/* TODO an alternative way is to fork and let the child
* do the test. */
/* TODO This function shall block calls to brk and sbrk. */
prev_brk = sbrk(n);
if (prev_brk == (void*)-1)
return 1;
if (brk(prev_brk))
return 1; /* Should not happen. */
{
/* TODO This function shall block calls to signal.h functions. */
sigset_t old_mask;
sigset_t new_mask;
void* old_sigsegv_handler;
if (sigemptyset(&new_mask) || sigaddset(&new_mask, SIGSEGV))
return 1;
old_sigsegv_handler = signal(SIGSEGV, SIG_DFL);
/* Sorry, we cannot have a signal handler, the OS kernel
* will make the CPU halt and catch fire until we die. */
if (old_sigsegv_handler == SIG_ERR)
return 1;
if (pthread_sigmask(SIG_UNBLOCK, &new_mask, &old_mask))
return 1;
(void) alloca((size_t)n);
if (pthread_sigmask(SIG_SETMASK, &old_mask, NULL))
return 1;
if (signal(SIGSEGV, old_sigsegv_handler) == SIG_ERR)
return 1;
}
return 0;
}
/**
* Check for execution stack overflow. If the stack of
* overflow, or will overflow, the program shall abort.
*
* It is possible that the process is killed by SIGSEGV
* instead of aborting.
*
* This is a Plan 9 from Bell Labs extension.
*
* @etymology I (need) addition (stack) space.
*
* @param n The number of bytes the stack will grow by.
* 0 can be used to check for a current stack
* overflow. Must be non-negative.
*
* @since Always.
*/
void (needstack)(int n)
{
int tty;
if (stack_will_overflow((intptr_t)n) == 0)
return;
tty = isatty(STDERR_FILENO);
fprintf(stderr,
_("%(\033[00;01m%)%s%(\033[00m%): "
"%(\033[31m%)%s%(\033[00m%)"
"%(: %(\033[31m%)hinted stack growth: %i bytes%(\033[00m%)%)\n"),
tty, program_invocation_name, tty,
tty, (n ? _("imminent stack overflow detected") : _("stack overflow detected")), tty,
n != 0, tty, n, tty);
fflush(NULL); /* Flush all streams. */
abort();
}
/**
* This function is called if the `needstack` macro is called.
* It enhances the `needstack` function with detail on where
* the program failed.
*
* You should not use this function directly.
*
* @param n The number of bytes the stack will grow by. 0 can be used
* to check for a current stack overflow. Must be non-negative.
* @param file The filename of the source cose whence the check was made.
* @param line The line in the source code whence the check was made.
* @param func The function in the source code whence the check was made,
* `NULL` if unknown (C99 is required.)
*/
void __needstack(int n, const char* file, int line, const char* func)
{
int tty;
if (stack_will_overflow((intptr_t)n) == 0)
return;
tty = isatty(STDERR_FILENO);
fprintf(stderr,
_("%(\033[00;01m%)%s%(\033[00m%): "
"%(\033[31m%)%s%(\033[00m%) "
"at line %(\033[33m%)%i%(\033[00m%) "
"of file %(\033[35m%)%s%(\033[00m%)"
"%(, function %(\033[1;34m%)%s%(\033[00m%)%)"
"%(: %(\033[31m%)hinted stack growth: %i bytes%(\033[00m%)%)\n"),
tty, program_invocation_name, tty,
tty, (n ? _("imminent stack overflow detected") : _("stack overflow detected")), tty,
tty, line, tty,
tty, file, tty,
func != NULL, tty, func, tty,
n != 0, tty, n, tty);
fflush(NULL); /* Flush all streams. */
abort();
}
