/* $OpenBSD: atexit.c,v 1.14 2007/09/05 20:47:47 chl Exp $ */
/*
* Copyright (c) 2002 Daniel Hartmeier
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
*/
#include <sys/types.h>
#include <sys/mman.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "atexit.h"
#include "private/thread_private.h"
int __atexit_invalid = 1;
struct atexit *__atexit;
/*
* TODO: Read this before upstreaming:
*
* As of Apr 2014 there is a bug regaring function type detection logic in
* Free/Open/NetBSD implementations of __cxa_finalize().
*
* What it is about:
* First of all there are two kind of atexit handlers:
* 1) void handler(void) - this is the regular type
* available for to user via atexit(.) function call.
*
* 2) void internal_handler(void*) - this is the type
* __cxa_atexit() function expects. This handler is used
* by C++ compiler to register static destructor calls.
* Note that calling this function as the handler of type (1)
* results in incorrect this pointer in static d-tors.
*
* What is wrong with BSD implementations:
*
* They use dso argument to identify the handler type. The problem
* with it is dso is also used to identify the handlers associated
* with particular dynamic library and allow __cxa_finalize to call correct
* set of functions on dlclose(). And it cannot identify both.
*
* What is correct way to identify function type?
*
* Consider this:
* 1. __cxa_finalize and __cxa_atexit are part of libc and do not have access to hidden
* &__dso_handle.
* 2. __cxa_atexit has only 3 arguments: function pointer, function argument, dso.
* none of them can be reliably used to pass information about handler type.
* 3. following http://www.codesourcery.com/cxx-abi/abi.html#dso-dtor (3.3.5.3 - B)
* translation of user atexit -> __cxa_atexit(f, NULL, NULL) results in crashes
* on exit() after dlclose() of a library with an atexit() call.
*
* One way to resolve this is to always call second form of handler, which will
* result in storing unused argument in register/stack depending on architecture
* and should not present any problems.
*
* Another way is to make them dso-local in one way or the other.
*/
/*
* Function pointers are stored in a linked list of pages. The list
* is initially empty, and pages are allocated on demand. The first
* function pointer in the first allocated page (the last one in
* the linked list) was reserved for the cleanup function.
*
* Outside the following functions, all pages are mprotect()'ed
* to prevent unintentional/malicious corruption.
*/
/*
* Register a function to be performed at exit or when a shared object
* with the given dso handle is unloaded dynamically. Also used as
* the backend for atexit(). For more info on this API, see:
*
* http://www.codesourcery.com/cxx-abi/abi.html#dso-dtor
*/
int
__cxa_atexit(void (*func)(void *), void *arg, void *dso)
{
struct atexit *p = __atexit;
struct atexit_fn *fnp;
size_t pgsize = sysconf(_SC_PAGESIZE);
int ret = -1;
if (pgsize < sizeof(*p))
return (-1);
_ATEXIT_LOCK();
p = __atexit;
if (p != NULL) {
if (p->ind + 1 >= p->max)
p = NULL;
else if (mprotect(p, pgsize, PROT_READ | PROT_WRITE))
goto unlock;
}
if (p == NULL) {
p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE,
MAP_ANON | MAP_PRIVATE, -1, 0);
if (p == MAP_FAILED)
goto unlock;
if (__atexit == NULL) {
memset(&p->fns[0], 0, sizeof(p->fns[0]));
p->ind = 1;
} else
p->ind = 0;
p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) /
sizeof(p->fns[0]);
p->next = __atexit;
__atexit = p;
if (__atexit_invalid)
__atexit_invalid = 0;
}
fnp = &p->fns[p->ind++];
fnp->cxa_func = func;
fnp->fn_arg = arg;
fnp->fn_dso = dso;
if (mprotect(p, pgsize, PROT_READ))
goto unlock;
ret = 0;
unlock:
_ATEXIT_UNLOCK();
return (ret);
}
/*
* Call all handlers registered with __cxa_atexit() for the shared
* object owning 'dso'.
* Note: if 'dso' is NULL, then all remaining handlers are called.
*/
void
__cxa_finalize(void *dso)
{
struct atexit *p, *q, *original_atexit;
struct atexit_fn fn;
int n, pgsize = getpagesize(), original_ind;
static int call_depth;
if (__atexit_invalid)
return;
_ATEXIT_LOCK();
call_depth++;
p = original_atexit = __atexit;
n = original_ind = p != NULL ? p->ind : 0;
while (p != NULL) {
if (p->fns[n].cxa_func != NULL /* not called */
&& (dso == NULL || dso == p->fns[n].fn_dso)) { /* correct DSO */
/*
* Mark handler as having been already called to avoid
* dupes and loops, then call the appropriate function.
*/
fn = p->fns[n];
if (mprotect(p, pgsize, PROT_READ | PROT_WRITE) == 0) {
p->fns[n].cxa_func = NULL;
mprotect(p, pgsize, PROT_READ);
}
_ATEXIT_UNLOCK();
(*fn.cxa_func)(fn.fn_arg);
_ATEXIT_LOCK();
// check for new atexit handlers
if ((__atexit->ind != original_ind) || (__atexit != original_atexit)) {
// need to restart now to preserve correct
// call order - LIFO
p = original_atexit = __atexit;
n = original_ind = p->ind;
continue;
}
}
if (n == 0) {
p = p->next;
n = p != NULL ? p->ind : 0;
} else {
--n;
}
}
--call_depth;
/*
* If called via exit(), unmap the pages since we have now run
* all the handlers. We defer this until calldepth == 0 so that
* we don't unmap things prematurely if called recursively.
*/
if (dso == NULL && call_depth == 0) {
for (p = __atexit; p != NULL; ) {
q = p;
p = p->next;
munmap(q, pgsize);
}
__atexit = NULL;
}
_ATEXIT_UNLOCK();
}
/*
* Register the cleanup function
*/
void
__atexit_register_cleanup(void (*func)(void))
{
struct atexit *p;
size_t pgsize = sysconf(_SC_PAGESIZE);
if (pgsize < sizeof(*p))
return;
_ATEXIT_LOCK();
p = __atexit;
while (p != NULL && p->next != NULL)
p = p->next;
if (p == NULL) {
p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE,
MAP_ANON | MAP_PRIVATE, -1, 0);
if (p == MAP_FAILED)
goto unlock;
p->ind = 1;
p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) /
sizeof(p->fns[0]);
p->next = NULL;
__atexit = p;
} else {
if (mprotect(p, pgsize, PROT_READ | PROT_WRITE))
goto unlock;
}
p->fns[0].cxa_func = (void (*)(void*))func;
p->fns[0].fn_arg = NULL;
p->fns[0].fn_dso = NULL;
mprotect(p, pgsize, PROT_READ);
unlock:
_ATEXIT_UNLOCK();
}