bpf: Add bpf_line_info support

This patch adds bpf_line_info support.

It accepts an array of bpf_line_info objects during BPF_PROG_LOAD.
The "line_info", "line_info_cnt" and "line_info_rec_size" are added
to the "union bpf_attr".  The "line_info_rec_size" makes
bpf_line_info extensible in the future.

The new "check_btf_line()" ensures the userspace line_info is valid
for the kernel to use.

When the verifier is translating/patching the bpf_prog (through
"bpf_patch_insn_single()"), the line_infos' insn_off is also
adjusted by the newly added "bpf_adj_linfo()".

If the bpf_prog is jited, this patch also provides the jited addrs (in
aux->jited_linfo) for the corresponding line_info.insn_off.
"bpf_prog_fill_jited_linfo()" is added to fill the aux->jited_linfo.
It is currently called by the x86 jit.  Other jits can also use
"bpf_prog_fill_jited_linfo()" and it will be done in the followup patches.
In the future, if it deemed necessary, a particular jit could also provide
its own "bpf_prog_fill_jited_linfo()" implementation.

A few "*line_info*" fields are added to the bpf_prog_info such
that the user can get the xlated line_info back (i.e. the line_info
with its insn_off reflecting the translated prog).  The jited_line_info
is available if the prog is jited.  It is an array of __u64.
If the prog is not jited, jited_line_info_cnt is 0.

The verifier's verbose log with line_info will be done in
a follow up patch.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 77 insertions, 6 deletions

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index aa05aa38f4a8..19c88cff7880 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1215,6 +1215,7 @@ static void __bpf_prog_put(struct bpf_prog *prog, bool do_idr_lock)
 		bpf_prog_kallsyms_del_all(prog);
 		btf_put(prog->aux->btf);
 		kvfree(prog->aux->func_info);
+		bpf_prog_free_linfo(prog);
 
 		call_rcu(&prog->aux->rcu, __bpf_prog_put_rcu);
 	}
@@ -1439,7 +1440,7 @@ bpf_prog_load_check_attach_type(enum bpf_prog_type prog_type,
 }
 
 /* last field in 'union bpf_attr' used by this command */
-#define	BPF_PROG_LOAD_LAST_FIELD func_info_cnt
+#define	BPF_PROG_LOAD_LAST_FIELD line_info_cnt
 
 static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
 {
@@ -1560,6 +1561,7 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
 	return err;
 
 free_used_maps:
+	bpf_prog_free_linfo(prog);
 	kvfree(prog->aux->func_info);
 	btf_put(prog->aux->btf);
 	bpf_prog_kallsyms_del_subprogs(prog);
@@ -2041,6 +2043,37 @@ static struct bpf_insn *bpf_insn_prepare_dump(const struct bpf_prog *prog)
 	return insns;
 }
 
+static int set_info_rec_size(struct bpf_prog_info *info)
+{
+	/*
+	 * Ensure info.*_rec_size is the same as kernel expected size
+	 *
+	 * or
+	 *
+	 * Only allow zero *_rec_size if both _rec_size and _cnt are
+	 * zero.  In this case, the kernel will set the expected
+	 * _rec_size back to the info.
+	 */
+
+	if ((info->func_info_cnt || info->func_info_rec_size) &&
+	    info->func_info_rec_size != sizeof(struct bpf_func_info))
+		return -EINVAL;
+
+	if ((info->line_info_cnt || info->line_info_rec_size) &&
+	    info->line_info_rec_size != sizeof(struct bpf_line_info))
+		return -EINVAL;
+
+	if ((info->jited_line_info_cnt || info->jited_line_info_rec_size) &&
+	    info->jited_line_info_rec_size != sizeof(__u64))
+		return -EINVAL;
+
+	info->func_info_rec_size = sizeof(struct bpf_func_info);
+	info->line_info_rec_size = sizeof(struct bpf_line_info);
+	info->jited_line_info_rec_size = sizeof(__u64);
+
+	return 0;
+}
+
 static int bpf_prog_get_info_by_fd(struct bpf_prog *prog,
 				   const union bpf_attr *attr,
 				   union bpf_attr __user *uattr)
@@ -2083,11 +2116,9 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog,
 				return -EFAULT;
 	}
 
-	if ((info.func_info_cnt || info.func_info_rec_size) &&
-	    info.func_info_rec_size != sizeof(struct bpf_func_info))
-		return -EINVAL;
-
-	info.func_info_rec_size = sizeof(struct bpf_func_info);
+	err = set_info_rec_size(&info);
+	if (err)
+		return err;
 
 	if (!capable(CAP_SYS_ADMIN)) {
 		info.jited_prog_len = 0;
@@ -2095,6 +2126,8 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog,
 		info.nr_jited_ksyms = 0;
 		info.nr_jited_func_lens = 0;
 		info.func_info_cnt = 0;
+		info.line_info_cnt = 0;
+		info.jited_line_info_cnt = 0;
 		goto done;
 	}
 
@@ -2251,6 +2284,44 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog,
 		}
 	}
 
+	ulen = info.line_info_cnt;
+	info.line_info_cnt = prog->aux->nr_linfo;
+	if (info.line_info_cnt && ulen) {
+		if (bpf_dump_raw_ok()) {
+			__u8 __user *user_linfo;
+
+			user_linfo = u64_to_user_ptr(info.line_info);
+			ulen = min_t(u32, info.line_info_cnt, ulen);
+			if (copy_to_user(user_linfo, prog->aux->linfo,
+					 info.line_info_rec_size * ulen))
+				return -EFAULT;
+		} else {
+			info.line_info = 0;
+		}
+	}
+
+	ulen = info.jited_line_info_cnt;
+	if (prog->aux->jited_linfo)
+		info.jited_line_info_cnt = prog->aux->nr_linfo;
+	else
+		info.jited_line_info_cnt = 0;
+	if (info.jited_line_info_cnt && ulen) {
+		if (bpf_dump_raw_ok()) {
+			__u64 __user *user_linfo;
+			u32 i;
+
+			user_linfo = u64_to_user_ptr(info.jited_line_info);
+			ulen = min_t(u32, info.jited_line_info_cnt, ulen);
+			for (i = 0; i < ulen; i++) {
+				if (put_user((__u64)(long)prog->aux->jited_linfo[i],
+					     &user_linfo[i]))
+					return -EFAULT;
+			}
+		} else {
+			info.jited_line_info = 0;
+		}
+	}
+
 done:
 	if (copy_to_user(uinfo, &info, info_len) ||
 	    put_user(info_len, &uattr->info.info_len))