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llext: add reference counting

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Extend the llext_load() / llext_unload() API to let it be called
repeatedly for the same extension to increment or decrement its
reference counter respectively. We use a mutex to protect the counter
and make both llext_load() and llext_unload() return the use-count to
let the caller identify when the first loading and the last unloading
took place.

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
This commit is contained in:
Guennadi Liakhovetski 2023-11-03 14:16:16 +01:00 • committed by Anas Nashif
commit a2acd7b2fb
4 changed files with 55 additions and 21 deletions
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65
subsys/llext/llext.c
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@ -807,12 +807,25 @@ out:
return ret;
}
static struct k_mutex llext_lock = Z_MUTEX_INITIALIZER(llext_lock);
int llext_load(struct llext_loader *ldr, const char *name, struct llext **ext,
struct llext_load_param *ldr_parm)
{
int ret;
elf_ehdr_t ehdr;
k_mutex_lock(&llext_lock, K_FOREVER);
if (*ext) {
/* The use count is at least 1 */
ret = (*ext)->use_count++;
k_mutex_unlock(&llext_lock);
return ret;
}
k_mutex_unlock(&llext_lock);
ret = llext_seek(ldr, 0);
if (ret != 0) {
LOG_ERR("Failed to seek for ELF header");
@ -848,40 +861,58 @@ int llext_load(struct llext_loader *ldr, const char *name, struct llext **ext,
ldr->hdr = ehdr;
ret = do_llext_load(ldr, *ext, ldr_parm);
if (ret < 0)
return ret;
strncpy((*ext)->name, name, sizeof((*ext)->name));
(*ext)->name[sizeof((*ext)->name) - 1] = '\0';
(*ext)->use_count++;
sys_slist_append(&_llext_list, &(*ext)->_llext_list);
LOG_INF("Loaded extension %s", (*ext)->name);
break;
default:
LOG_ERR("Unsupported elf file type %x", ehdr.e_type);
*ext = NULL;
return -EINVAL;
}
if (ret == 0) {
strncpy((*ext)->name, name, sizeof((*ext)->name));
(*ext)->name[sizeof((*ext)->name) - 1] = '\0';
sys_slist_append(&_llext_list, &(*ext)->_llext_list);
LOG_INF("Loaded extension %s", (*ext)->name);
}
return ret;
return 0;
}
void llext_unload(struct llext *ext)
int llext_unload(struct llext **ext)
{
__ASSERT(ext, "Expected non-null extension");
__ASSERT(*ext, "Expected non-null extension");
struct llext *tmp = *ext;
sys_slist_find_and_remove(&_llext_list, &ext->_llext_list);
k_mutex_lock(&llext_lock, K_FOREVER);
__ASSERT(tmp->use_count, "A valid LLEXT cannot have a zero use-count!");
if (tmp->use_count-- != 1) {
unsigned int ret = tmp->use_count;
k_mutex_unlock(&llext_lock);
return ret;
}
/* FIXME: protect the global list */
sys_slist_find_and_remove(&_llext_list, &tmp->_llext_list);
*ext = NULL;
k_mutex_unlock(&llext_lock);
for (int i = 0; i < LLEXT_MEM_COUNT; i++) {
if (ext->mem_on_heap[i]) {
if (tmp->mem_on_heap[i]) {
LOG_DBG("freeing memory region %d", i);
k_heap_free(&llext_heap, ext->mem[i]);
ext->mem[i] = NULL;
k_heap_free(&llext_heap, tmp->mem[i]);
tmp->mem[i] = NULL;
}
}
k_heap_free(&llext_heap, ext->sym_tab.syms);
k_heap_free(&llext_heap, tmp->sym_tab.syms);
k_heap_free(&llext_heap, tmp);
k_heap_free(&llext_heap, ext);
return 0;
}
int llext_call_fn(struct llext *ext, const char *sym_name)