kernel/bpf/check_btf.c

Source file repositories/reference/linux-study-clean/kernel/bpf/check_btf.c

File Facts

System
Linux kernel
Corpus path
kernel/bpf/check_btf.c
Extension
.c
Size
11775 bytes
Lines
464
Domain
Core OS
Bucket
Scheduler, Processes, Timers, Sync, And Syscalls
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

if (env->subprog_info[i].has_ld_abs) {
			verbose(env, "LD_ABS is not allowed in subprogs without BTF\n");
			return -EINVAL;
		}
		if (env->subprog_info[i].has_tail_call) {
			verbose(env, "tail_call is not allowed in subprogs without BTF\n");
			return -EINVAL;
		}
	}
	return 0;
}

/* The minimum supported BTF func info size */
#define MIN_BPF_FUNCINFO_SIZE	8
#define MAX_FUNCINFO_REC_SIZE	252

static int check_btf_func_early(struct bpf_verifier_env *env,
				const union bpf_attr *attr,
				bpfptr_t uattr)
{
	u32 krec_size = sizeof(struct bpf_func_info);
	const struct btf_type *type, *func_proto;
	u32 i, nfuncs, urec_size, min_size;
	struct bpf_func_info *krecord;
	struct bpf_prog *prog;
	const struct btf *btf;
	u32 prev_offset = 0;
	bpfptr_t urecord;
	int ret = -ENOMEM;

	nfuncs = attr->func_info_cnt;
	if (!nfuncs) {
		if (check_abnormal_return(env))
			return -EINVAL;
		return 0;
	}

	urec_size = attr->func_info_rec_size;
	if (urec_size < MIN_BPF_FUNCINFO_SIZE ||
	    urec_size > MAX_FUNCINFO_REC_SIZE ||
	    urec_size % sizeof(u32)) {
		verbose(env, "invalid func info rec size %u\n", urec_size);
		return -EINVAL;
	}

	prog = env->prog;
	btf = prog->aux->btf;

	urecord = make_bpfptr(attr->func_info, uattr.is_kernel);
	min_size = min_t(u32, krec_size, urec_size);

	krecord = kvcalloc(nfuncs, krec_size, GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
	if (!krecord)
		return -ENOMEM;

	for (i = 0; i < nfuncs; i++) {
		ret = bpf_check_uarg_tail_zero(urecord, krec_size, urec_size);
		if (ret) {
			if (ret == -E2BIG) {
				verbose(env, "nonzero tailing record in func info");
				/* set the size kernel expects so loader can zero
				 * out the rest of the record.
				 */
				if (copy_to_bpfptr_offset(uattr,
							  offsetof(union bpf_attr, func_info_rec_size),
							  &min_size, sizeof(min_size)))
					ret = -EFAULT;
			}
			goto err_free;
		}

		if (copy_from_bpfptr(&krecord[i], urecord, min_size)) {
			ret = -EFAULT;
			goto err_free;
		}

		/* check insn_off */
		ret = -EINVAL;
		if (i == 0) {
			if (krecord[i].insn_off) {
				verbose(env,
					"nonzero insn_off %u for the first func info record",
					krecord[i].insn_off);
				goto err_free;
			}
		} else if (krecord[i].insn_off <= prev_offset) {
			verbose(env,
				"same or smaller insn offset (%u) than previous func info record (%u)",
				krecord[i].insn_off, prev_offset);
			goto err_free;

Annotation

Implementation Notes