+struct bus_body_part *message_append_part(sd_bus_message *m) {
+ struct bus_body_part *part;
+
+ assert(m);
+
+ if (m->poisoned)
+ return NULL;
+
+ if (m->n_body_parts <= 0) {
+ part = &m->body;
+ zero(*part);
+ } else {
+ assert(m->body_end);
+
+ part = new0(struct bus_body_part, 1);
+ if (!part) {
+ m->poisoned = true;
+ return NULL;
+ }
+
+ m->body_end->next = part;
+ }
+
+ part->memfd = -1;
+ m->body_end = part;
+ m->n_body_parts ++;
+
+ return part;
+}
+
+static void part_zero(struct bus_body_part *part, size_t sz) {
+ assert(part);
+ assert(sz > 0);
+ assert(sz < 8);
+
+ part->data = NULL;
+ part->size = sz;
+}
+
+static int part_make_space(
+ struct sd_bus_message *m,
+ struct bus_body_part *part,
+ size_t sz,
+ void **q) {
+
+ void *n;
+ int r;
+
+ assert(m);
+ assert(part);
+ assert(!part->sealed);
+
+ if (m->poisoned)
+ return -ENOMEM;
+
+ if (!part->data && part->memfd < 0)
+ part->memfd = bus_kernel_pop_memfd(m->bus, &part->data, &part->mapped);
+
+ if (part->memfd >= 0) {
+ uint64_t u = sz;
+
+ r = ioctl(part->memfd, KDBUS_CMD_MEMFD_SIZE_SET, &u);
+ if (r < 0) {
+ m->poisoned = true;
+ return -errno;
+ }
+
+ if (sz > part->mapped) {
+ size_t psz = PAGE_ALIGN(sz);
+
+ if (part->mapped <= 0)
+ n = mmap(NULL, psz, PROT_READ|PROT_WRITE, MAP_SHARED, part->memfd, 0);
+ else
+ n = mremap(part->data, part->mapped, psz, MREMAP_MAYMOVE);
+
+ if (n == MAP_FAILED) {
+ m->poisoned = true;
+ return -errno;
+ }
+
+ part->mapped = psz;
+ part->data = n;
+ }
+ } else {
+ n = realloc(part->data, sz);
+ if (!n) {
+ m->poisoned = true;
+ return -ENOMEM;
+ }
+
+ part->data = n;
+ part->free_this = true;
+ }
+
+ if (q)
+ *q = part->data ? (uint8_t*) part->data + part->size : NULL;
+
+ part->size = sz;
+ return 0;
+}
+