bpf: Assign ID to vmlinux BTF and return extra info for BTF in GET_OBJ_INFO

mainline inclusion
from mainline-5.11-rc1
commit 53297220
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5329722057d41aebc31e391907a501feaa42f7d9

-------------------------------------------------

Allocate ID for vmlinux BTF. This makes it visible when iterating over all BTF
objects in the system. To allow distinguishing vmlinux BTF (and later kernel
module BTF) from user-provided BTFs, expose extra kernel_btf flag, as well as
BTF name ("vmlinux" for vmlinux BTF, will equal to module's name for module
BTF).  We might want to later allow specifying BTF name for user-provided BTFs
as well, if that makes sense. But currently this is reserved only for
in-kernel BTFs.

Having in-kernel BTFs exposed IDs will allow to extend BPF APIs that require
in-kernel BTF type with ability to specify BTF types from kernel modules, not
just vmlinux BTF. This will be implemented in a follow up patch set for
fentry/fexit/fmod_ret/lsm/etc.
Signed-off-by: NAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NSong Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201110011932.3201430-3-andrii@kernel.org
(cherry picked from commit 53297220)
Signed-off-by: NWang Yufen <wangyufen@huawei.com>

include/uapi/linux/bpf.h

@@ -4610,6 +4610,9 @@ struct bpf_btf_info {
 	__aligned_u64 btf;
 	__u32 btf_size;
 	__u32 id;
+	__aligned_u64 name;
+	__u32 name_len;
+	__u32 kernel_btf;
 } __attribute__((aligned(8)));
 
 struct bpf_link_info {

kernel/bpf/btf.c

@@ -214,6 +214,8 @@ struct btf {
 	struct btf *base_btf;
 	u32 start_id; /* first type ID in this BTF (0 for base BTF) */
 	u32 start_str_off; /* first string offset (0 for base BTF) */
+	char name[MODULE_NAME_LEN];
+	bool kernel_btf;
 };
 
 enum verifier_phase {
@@ -4428,6 +4430,8 @@ struct btf *btf_parse_vmlinux(void)
 
 	btf->data = __start_BTF;
 	btf->data_size = __stop_BTF - __start_BTF;
+	btf->kernel_btf = true;
+	snprintf(btf->name, sizeof(btf->name), "vmlinux");
 
 	err = btf_parse_hdr(env);
 	if (err)
@@ -4453,8 +4457,13 @@ struct btf *btf_parse_vmlinux(void)
 
 	bpf_struct_ops_init(btf, log);
 
-	btf_verifier_env_free(env);
 	refcount_set(&btf->refcnt, 1);
+
+	err = btf_alloc_id(btf);
+	if (err)
+		goto errout;
+
+	btf_verifier_env_free(env);
 	return btf;
 
 errout:
@@ -5567,7 +5576,9 @@ int btf_get_info_by_fd(const struct btf *btf,
 	struct bpf_btf_info info;
 	u32 info_copy, btf_copy;
 	void __user *ubtf;
-	u32 uinfo_len;
+	char __user *uname;
+	u32 uinfo_len, uname_len, name_len;
+	int ret = 0;
 
 	uinfo = u64_to_user_ptr(attr->info.info);
 	uinfo_len = attr->info.info_len;
@@ -5584,11 +5595,37 @@ int btf_get_info_by_fd(const struct btf *btf,
 		return -EFAULT;
 	info.btf_size = btf->data_size;
 
+	info.kernel_btf = btf->kernel_btf;
+
+	uname = u64_to_user_ptr(info.name);
+	uname_len = info.name_len;
+	if (!uname ^ !uname_len)
+		return -EINVAL;
+
+	name_len = strlen(btf->name);
+	info.name_len = name_len;
+
+	if (uname) {
+		if (uname_len >= name_len + 1) {
+			if (copy_to_user(uname, btf->name, name_len + 1))
+				return -EFAULT;
+		} else {
+			char zero = '\0';
+
+			if (copy_to_user(uname, btf->name, uname_len - 1))
+				return -EFAULT;
+			if (put_user(zero, uname + uname_len - 1))
+				return -EFAULT;
+			/* let user-space know about too short buffer */
+			ret = -ENOSPC;
+		}
+	}
+
 	if (copy_to_user(uinfo, &info, info_copy) ||
 	    put_user(info_copy, &uattr->info.info_len))
 		return -EFAULT;
 
-	return 0;
+	return ret;
 }
 
 int btf_get_fd_by_id(u32 id)

tools/include/uapi/linux/bpf.h

@@ -4609,6 +4609,9 @@ struct bpf_btf_info {
 	__aligned_u64 btf;
 	__u32 btf_size;
 	__u32 id;
+	__aligned_u64 name;
+	__u32 name_len;
+	__u32 kernel_btf;
 } __attribute__((aligned(8)));
 
 struct bpf_link_info {