Function malloc_dbg

freebsd/kern/kern_malloc.c:500–561

#ifdef MALLOC_DEBUG
static int
malloc_dbg(caddr_t *vap, size_t *sizep, struct malloc_type *mtp,
    int flags)
{
#ifdef INVARIANTS
	int indx;

	KASSERT(mtp->ks_version == M_VERSION, ("malloc: bad malloc type version"));
	/*
	 * Check that exactly one of M_WAITOK or M_NOWAIT is specified.
	 */
	indx = flags & (M_WAITOK | M_NOWAIT);
	if (indx != M_NOWAIT && indx != M_WAITOK) {
		static	struct timeval lasterr;
		static	int curerr, once;
		if (once == 0 && ppsratecheck(&lasterr, &curerr, 1)) {
			printf("Bad malloc flags: %x\n", indx);
			kdb_backtrace();
			flags |= M_WAITOK;
			once++;
		}
	}
#endif
#ifdef MALLOC_MAKE_FAILURES
	if ((flags & M_NOWAIT) && (malloc_failure_rate != 0)) {
		atomic_add_int(&malloc_nowait_count, 1);
		if ((malloc_nowait_count % malloc_failure_rate) == 0) {
			atomic_add_int(&malloc_failure_count, 1);
			*vap = NULL;
			return (EJUSTRETURN);
		}
	}
#endif
	if (flags & M_WAITOK) {
		KASSERT(curthread->td_intr_nesting_level == 0,
		   ("malloc(M_WAITOK) in interrupt context"));
		if (__predict_false(!THREAD_CAN_SLEEP())) {
#ifdef EPOCH_TRACE
			epoch_trace_list(curthread);
#endif
			KASSERT(1, 
			    ("malloc(M_WAITOK) with sleeping prohibited"));
		}
	}
	KASSERT(curthread->td_critnest == 0 || SCHEDULER_STOPPED(),
	    ("malloc: called with spinlock or critical section held"));

#ifdef DEBUG_MEMGUARD
	if (memguard_cmp_mtp(mtp, *sizep)) {
		*vap = memguard_alloc(*sizep, flags);
		if (*vap != NULL)
			return (EJUSTRETURN);
		/* This is unfortunate but should not be fatal. */
	}
#endif

#ifdef DEBUG_REDZONE
	*sizep = redzone_size_ntor(*sizep);