[bpf-next,2/5] bpf: Detect if a program needs its program ID.

Commit Message

Kui-Feng Lee Jan. 26, 2022, 9:48 p.m. UTC

Scan BPF bytecode to detect if a program calls any functions requiring
a program ID.  So far, bpf_get_attach_cookie() is the only function
that needs a program ID.

Signed-off-by: Kui-Feng Lee <[e-mail]>
---
 include/linux/filter.h  | 3 ++-
 kernel/bpf/trampoline.c | 7 ++++---
 kernel/bpf/verifier.c   | 3 +++
 3 files changed, 9 insertions(+), 4 deletions(-)

Patch

diff --git a/include/linux/filter.h b/include/linux/filter.h
index d23e999dc032..4433c5d1bc19 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -572,7 +572,8 @@  struct bpf_prog {
 				has_callchain_buf:1, /* callchain buffer allocated? */
 				enforce_expected_attach_type:1, /* Enforce expected_attach_type checking at attach time */
 				call_get_stack:1, /* Do we call bpf_get_stack() or bpf_get_stackid() */
-				call_get_func_ip:1; /* Do we call get_func_ip() */
+				call_get_func_ip:1, /* Do we call get_func_ip() */
+				need_prog_id:1; /* Do we need program ID? */
 	enum bpf_prog_type	type;		/* Type of BPF program */
 	enum bpf_attach_type	expected_attach_type; /* For some prog types */
 	u32			len;		/* Number of filter blocks */
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 4b6974a195c1..c65622e4216c 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -181,7 +181,7 @@  static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
 }
 
 static struct bpf_tramp_progs *
-bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total, bool *ip_arg)
+bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total, bool *ip_arg, bool *prog_id)
 {
 	const struct bpf_prog_aux *aux;
 	struct bpf_tramp_progs *tprogs;
@@ -200,6 +200,7 @@  bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total, bool *ip_a
 
 		hlist_for_each_entry(aux, &tr->progs_hlist[kind], tramp_hlist) {
 			*ip_arg |= aux->prog->call_get_func_ip;
+			*prog_id |= aux->prog->need_prog_id;
 			*progs++ = aux->prog;
 		}
 	}
@@ -344,10 +345,10 @@  static int bpf_trampoline_update(struct bpf_trampoline *tr)
 	struct bpf_tramp_image *im;
 	struct bpf_tramp_progs *tprogs;
 	u32 flags = BPF_TRAMP_F_RESTORE_REGS;
-	bool ip_arg = false;
+	bool ip_arg = false, prog_id = false;
 	int err, total;
 
-	tprogs = bpf_trampoline_get_progs(tr, &total, &ip_arg);
+	tprogs = bpf_trampoline_get_progs(tr, &total, &ip_arg, &prog_id);
 	if (IS_ERR(tprogs))
 		return PTR_ERR(tprogs);
 
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ff91f5038010..0359242e2a81 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -6812,6 +6812,9 @@  static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 		env->prog->call_get_func_ip = true;
 	}
 
+	if (func_id == BPF_FUNC_get_attach_cookie)
+		env->prog->need_prog_id = true;
+
 	if (changes_data)
 		clear_all_pkt_pointers(env);
 	return 0;