@@ -15,3 +15,11 @@ Description:
information with description of all internal kernel types. See
Documentation/bpf/btf.rst for detailed description of format
itself.
+
+What: /sys/kernel/btf/<module-name>
+Date: Nov 2020
+KernelVersion: 5.11
+Contact: bpf@vger.kernel.org
+Description:
+ Read-only binary attribute exposing kernel module's BTF type
+ information as an add-on to the kernel's BTF (/sys/kernel/btf/vmlinux).
@@ -36,9 +36,11 @@ struct seq_operations;
struct bpf_iter_aux_info;
struct bpf_local_storage;
struct bpf_local_storage_map;
+struct kobject;
extern struct idr btf_idr;
extern spinlock_t btf_idr_lock;
+extern struct kobject *btf_kobj;
typedef int (*bpf_iter_init_seq_priv_t)(void *private_data,
struct bpf_iter_aux_info *aux);
@@ -475,6 +475,10 @@ struct module {
unsigned int num_bpf_raw_events;
struct bpf_raw_event_map *bpf_raw_events;
#endif
+#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+ unsigned int btf_data_size;
+ void *btf_data;
+#endif
#ifdef CONFIG_JUMP_LABEL
struct jump_entry *jump_entries;
unsigned int num_jump_entries;
@@ -23,6 +23,8 @@
#include <linux/perf_event.h>
#include <linux/bsearch.h>
#include <linux/btf_ids.h>
+#include <linux/kobject.h>
+#include <linux/sysfs.h>
#include <net/sock.h>
/* BTF (BPF Type Format) is the meta data format which describes
@@ -4477,6 +4479,75 @@ struct btf *btf_parse_vmlinux(void)
return ERR_PTR(err);
}
+static struct btf *btf_parse_module(const char *module_name, const void *data, unsigned int data_size)
+{
+ struct btf_verifier_env *env = NULL;
+ struct bpf_verifier_log *log;
+ struct btf *btf = NULL, *base_btf;
+ int err;
+
+ base_btf = bpf_get_btf_vmlinux();
+ if (IS_ERR(base_btf))
+ return base_btf;
+ if (!base_btf)
+ return ERR_PTR(-EINVAL);
+
+ env = kzalloc(sizeof(*env), GFP_KERNEL | __GFP_NOWARN);
+ if (!env)
+ return ERR_PTR(-ENOMEM);
+
+ log = &env->log;
+ log->level = BPF_LOG_KERNEL;
+
+ btf = kzalloc(sizeof(*btf), GFP_KERNEL | __GFP_NOWARN);
+ if (!btf) {
+ err = -ENOMEM;
+ goto errout;
+ }
+ env->btf = btf;
+
+ btf->base_btf = base_btf;
+ btf->start_id = base_btf->nr_types;
+ btf->start_str_off = base_btf->hdr.str_len;
+ btf->kernel_btf = true;
+ snprintf(btf->name, sizeof(btf->name), "%s", module_name);
+
+ btf->data = kvmalloc(data_size, GFP_KERNEL | __GFP_NOWARN);
+ if (!btf->data) {
+ err = -ENOMEM;
+ goto errout;
+ }
+ memcpy(btf->data, data, data_size);
+ btf->data_size = data_size;
+
+ err = btf_parse_hdr(env);
+ if (err)
+ goto errout;
+
+ btf->nohdr_data = btf->data + btf->hdr.hdr_len;
+
+ err = btf_parse_str_sec(env);
+ if (err)
+ goto errout;
+
+ err = btf_check_all_metas(env);
+ if (err)
+ goto errout;
+
+ btf_verifier_env_free(env);
+ refcount_set(&btf->refcnt, 1);
+ return btf;
+
+errout:
+ btf_verifier_env_free(env);
+ if (btf) {
+ kvfree(btf->data);
+ kvfree(btf->types);
+ kfree(btf);
+ }
+ return ERR_PTR(err);
+}
+
struct btf *bpf_prog_get_target_btf(const struct bpf_prog *prog)
{
struct bpf_prog *tgt_prog = prog->aux->dst_prog;
@@ -5650,3 +5721,126 @@ bool btf_id_set_contains(const struct btf_id_set *set, u32 id)
{
return bsearch(&id, set->ids, set->cnt, sizeof(u32), btf_id_cmp_func) != NULL;
}
+
+#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+struct btf_module {
+ struct list_head list;
+ struct module *module;
+ struct btf *btf;
+ struct bin_attribute *sysfs_attr;
+};
+
+static LIST_HEAD(btf_modules);
+static DEFINE_MUTEX(btf_module_mutex);
+
+static ssize_t
+btf_module_read(struct file *file, struct kobject *kobj,
+ struct bin_attribute *bin_attr,
+ char *buf, loff_t off, size_t len)
+{
+ const struct btf *btf = bin_attr->private;
+
+ memcpy(buf, btf->data + off, len);
+ return len;
+}
+
+static int btf_module_notify(struct notifier_block *nb, unsigned long op,
+ void *module)
+{
+ struct btf_module *btf_mod, *tmp;
+ struct module *mod = module;
+ struct btf *btf;
+ int err = 0;
+
+ if (mod->btf_data_size == 0 ||
+ (op != MODULE_STATE_COMING && op != MODULE_STATE_GOING))
+ goto out;
+
+ switch (op) {
+ case MODULE_STATE_COMING:
+ btf_mod = kzalloc(sizeof(*btf_mod), GFP_KERNEL);
+ if (!btf_mod) {
+ err = -ENOMEM;
+ goto out;
+ }
+ btf = btf_parse_module(mod->name, mod->btf_data, mod->btf_data_size);
+ if (IS_ERR(btf)) {
+ pr_warn("failed to validate module [%s] BTF: %ld\n",
+ mod->name, PTR_ERR(btf));
+ kfree(btf_mod);
+ err = PTR_ERR(btf);
+ goto out;
+ }
+ err = btf_alloc_id(btf);
+ if (err) {
+ btf_free(btf);
+ kfree(btf_mod);
+ goto out;
+ }
+
+ mutex_lock(&btf_module_mutex);
+ btf_mod->module = module;
+ btf_mod->btf = btf;
+ list_add(&btf_mod->list, &btf_modules);
+ mutex_unlock(&btf_module_mutex);
+
+ if (IS_ENABLED(CONFIG_SYSFS)) {
+ struct bin_attribute *attr;
+
+ attr = kzalloc(sizeof(*attr), GFP_KERNEL);
+ if (!attr)
+ goto out;
+
+ sysfs_bin_attr_init(attr);
+ attr->attr.name = btf->name;
+ attr->attr.mode = 0444;
+ attr->size = btf->data_size;
+ attr->private = btf;
+ attr->read = btf_module_read;
+
+ err = sysfs_create_bin_file(btf_kobj, attr);
+ if (err) {
+ pr_warn("failed to register module [%s] BTF in sysfs: %d\n",
+ mod->name, err);
+ kfree(attr);
+ err = 0;
+ goto out;
+ }
+
+ btf_mod->sysfs_attr = attr;
+ }
+
+ break;
+ case MODULE_STATE_GOING:
+ mutex_lock(&btf_module_mutex);
+ list_for_each_entry_safe(btf_mod, tmp, &btf_modules, list) {
+ if (btf_mod->module != module)
+ continue;
+
+ list_del(&btf_mod->list);
+ if (btf_mod->sysfs_attr)
+ sysfs_remove_bin_file(btf_kobj, btf_mod->sysfs_attr);
+ btf_put(btf_mod->btf);
+ kfree(btf_mod->sysfs_attr);
+ kfree(btf_mod);
+ break;
+ }
+ mutex_unlock(&btf_module_mutex);
+ break;
+ }
+out:
+ return notifier_from_errno(err);
+}
+
+static struct notifier_block btf_module_nb = {
+ .notifier_call = btf_module_notify,
+};
+
+static int __init btf_module_init(void)
+{
+ register_module_notifier(&btf_module_nb);
+ return 0;
+}
+
+fs_initcall(btf_module_init);
+#endif /* CONFIG_DEBUG_INFO_BTF_MODULES */
@@ -26,7 +26,7 @@ static struct bin_attribute bin_attr_btf_vmlinux __ro_after_init = {
.read = btf_vmlinux_read,
};
-static struct kobject *btf_kobj;
+struct kobject *btf_kobj;
static int __init btf_vmlinux_init(void)
{
@@ -380,6 +380,35 @@ static void *section_objs(const struct load_info *info,
return (void *)info->sechdrs[sec].sh_addr;
}
+/* Find a module section: 0 means not found. Ignores SHF_ALLOC flag. */
+static unsigned int find_any_sec(const struct load_info *info, const char *name)
+{
+ unsigned int i;
+
+ for (i = 1; i < info->hdr->e_shnum; i++) {
+ Elf_Shdr *shdr = &info->sechdrs[i];
+ if (strcmp(info->secstrings + shdr->sh_name, name) == 0)
+ return i;
+ }
+ return 0;
+}
+
+/*
+ * Find a module section, or NULL. Fill in number of "objects" in section.
+ * Ignores SHF_ALLOC flag.
+ */
+static __maybe_unused void *any_section_objs(const struct load_info *info,
+ const char *name,
+ size_t object_size,
+ unsigned int *num)
+{
+ unsigned int sec = find_any_sec(info, name);
+
+ /* Section 0 has sh_addr 0 and sh_size 0. */
+ *num = info->sechdrs[sec].sh_size / object_size;
+ return (void *)info->sechdrs[sec].sh_addr;
+}
+
/* Provided by the linker */
extern const struct kernel_symbol __start___ksymtab[];
extern const struct kernel_symbol __stop___ksymtab[];
@@ -3250,6 +3279,9 @@ static int find_module_sections(struct module *mod, struct load_info *info)
sizeof(*mod->bpf_raw_events),
&mod->num_bpf_raw_events);
#endif
+#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+ mod->btf_data = any_section_objs(info, ".BTF", 1, &mod->btf_data_size);
+#endif
#ifdef CONFIG_JUMP_LABEL
mod->jump_entries = section_objs(info, "__jump_table",
sizeof(*mod->jump_entries),