/*
* Null exception - catches bad memory accesses.
*/
static void
nullException(SIGNAL_ARGS(sig, ctx))
{
void *stackptr;
DEFINEFRAME();
/* Restore the signal handler if necessary */
restoreSyncSignalHandler(sig, nullException);
/* Clean up the synchronous signal state (just unblock this signal) */
unblockSignal(sig);
EXCEPTIONFRAME(frame, ctx);
#if defined(STACK_POINTER)
stackptr = (void *)STACK_POINTER(GET_SIGNAL_CONTEXT_POINTER(ctx));
#if defined(STACK_GROWS_UP)
if (currentJThread != NULL && stackptr >= currentJThread->stackEnd)
#else
if (currentJThread != NULL && stackptr <= currentJThread->stackBase)
#endif
stackOverflowHandler(EXCEPTIONFRAMEPTR);
else
#endif // STACK_POINTER
nullHandler(EXCEPTIONFRAMEPTR);
}
void *
malloc(size_t len)
{
struct __freelist *fp1, *fp2, *sfp1, *sfp2;
char *cp;
size_t s, avail;
/*
* Our minimum chunk size is the size of a pointer (plus the
* size of the "sz" field, but we don't need to account for
* this), otherwise we could not possibly fit a freelist entry
* into the chunk later.
*/
if (len < sizeof(struct __freelist) - sizeof(size_t))
len = sizeof(struct __freelist) - sizeof(size_t);
/*
* First, walk the free list and try finding a chunk that
* would match exactly. If we found one, we are done. While
* walking, note down the smallest chunk we found that would
* still fit the request -- we need it for step 2.
*
*/
for (s = 0, fp1 = __flp, fp2 = 0;
fp1;
fp2 = fp1, fp1 = fp1->nx) {
if (fp1->sz < len)
continue;
if (fp1->sz == len) {
/*
* Found it. Disconnect the chunk from the
* freelist, and return it.
*/
if (fp2)
fp2->nx = fp1->nx;
else
__flp = fp1->nx;
return &(fp1->nx);
}
else {
if (s == 0 || fp1->sz < s) {
/* this is the smallest chunk found so far */
s = fp1->sz;
sfp1 = fp1;
sfp2 = fp2;
}
}
}
/*
* Step 2: If we found a chunk on the freelist that would fit
* (but was too large), look it up again and use it, since it
* is our closest match now. Since the freelist entry needs
* to be split into two entries then, watch out that the
* difference between the requested size and the size of the
* chunk found is large enough for another freelist entry; if
* not, just enlarge the request size to what we have found,
* and use the entire chunk.
*/
if (s) {
if (s - len < sizeof(struct __freelist)) {
/* Disconnect it from freelist and return it. */
if (sfp2)
sfp2->nx = sfp1->nx;
else
__flp = sfp1->nx;
return &(sfp1->nx);
}
/*
* Split them up. Note that we leave the first part
* as the new (smaller) freelist entry, and return the
* upper portion to the caller. This saves us the
* work to fix up the freelist chain; we just need to
* fixup the size of the current entry, and note down
* the size of the new chunk before returning it to
* the caller.
*/
cp = (char *)sfp1;
s -= len;
cp += s;
sfp2 = (struct __freelist *)cp;
sfp2->sz = len;
sfp1->sz = s - sizeof(size_t);
return &(sfp2->nx);
}
/*
* Step 3: If the request could not be satisfied from a
* freelist entry, just prepare a new chunk. This means we
* need to obtain more memory first. The largest address just
* not allocated so far is remembered in the brkval variable.
* Under Unix, the "break value" was the end of the data
* segment as dynamically requested from the operating system.
* Since we don't have an operating system, just make sure
* that we don't collide with the stack.
*/
if (__brkval == 0)
__brkval = __malloc_heap_start;
cp = __malloc_heap_end;
if (cp == 0)
cp = STACK_POINTER() - __malloc_margin;
if (cp <= __brkval)
/*
* Memory exhausted.
*/
return 0;
avail = cp - __brkval;
/*
* Both tests below are needed to catch the case len >= 0xfffe.
*/
if (avail >= len && avail >= len + sizeof(size_t)) {
fp1 = (struct __freelist *)__brkval;
__brkval += len + sizeof(size_t);
//__brkval_maximum = __brkval;
fp1->sz = len;
return &(fp1->nx);
}
/*
* Step 4: There's no help, just fail. :-/
*/
return 0;
}
void *
realloc(void *ptr, size_t len)
{
struct __freelist *fp1, *fp2, *fp3, *ofp3;
char *cp, *cp1;
void *memp;
size_t s, incr;
/* Trivial case, required by C standard. */
if (ptr == 0)
return malloc(len);
cp1 = (char *)ptr;
cp1 -= sizeof(size_t);
fp1 = (struct __freelist *)cp1;
cp = (char *)ptr + len; /* new next pointer */
if (cp < cp1)
/* Pointer wrapped across top of RAM, fail. */
return 0;
/*
* See whether we are growing or shrinking. When shrinking,
* we split off a chunk for the released portion, and call
* free() on it. Therefore, we can only shrink if the new
* size is at least sizeof(struct __freelist) smaller than the
* previous size.
*/
if (len <= fp1->sz) {
/* The first test catches a possible unsigned int
* rollover condition. */
if (fp1->sz <= sizeof(struct __freelist) ||
len > fp1->sz - sizeof(struct __freelist))
return ptr;
fp2 = (struct __freelist *)cp;
fp2->sz = fp1->sz - len - sizeof(size_t);
fp1->sz = len;
free(&(fp2->nx));
return ptr;
}
/*
* If we get here, we are growing. First, see whether there
* is space in the free list on top of our current chunk.
*/
incr = len - fp1->sz;
cp = (char *)ptr + fp1->sz;
fp2 = (struct __freelist *)cp;
for (s = 0, ofp3 = 0, fp3 = __flp;
fp3;
ofp3 = fp3, fp3 = fp3->nx) {
if (fp3 == fp2 && fp3->sz + sizeof(size_t) >= incr) {
/* found something that fits */
if (fp3->sz + sizeof(size_t) - incr > sizeof(struct __freelist)) {
/* split off a new freelist entry */
cp = (char *)ptr + len;
fp2 = (struct __freelist *)cp;
fp2->nx = fp3->nx;
fp2->sz = fp3->sz - incr;
fp1->sz = len;
} else {
/* it just fits, so use it entirely */
fp1->sz += fp3->sz + sizeof(size_t);
fp2 = fp3->nx;
}
if (ofp3)
ofp3->nx = fp2;
else
__flp = fp2;
return ptr;
}
/*
* Find the largest chunk on the freelist while
* walking it.
*/
if (fp3->sz > s)
s = fp3->sz;
}
/*
* If we are the topmost chunk in memory, and there was no
* large enough chunk on the freelist that could be re-used
* (by a call to malloc() below), quickly extend the
* allocation area if possible, without need to copy the old
* data.
*/
if (__brkval == (char *)ptr + fp1->sz && len > s) {
cp = (char *)ptr + len;
cp1 = STACK_POINTER() - __malloc_margin;
if (cp < cp1) {
__brkval = cp;
//__brkval_maximum = cp;
fp1->sz = len;
return ptr;
}
/* If that failed, we are out of luck. */
return 0;
}
/*
* Call malloc() for a new chunk, then copy over the data, and
* release the old region.
*/
if ((memp = malloc(len)) == 0)
return 0;
memcpy(memp, ptr, fp1->sz);
free(ptr);
return memp;
}
