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))