From: Quentin Monnet <quentin.monnet@netronome.com>
Date: Sun, 7 Oct 2018 12:56:47 +0100
Subject: bpf: add verifier callback to get stack usage info for offloaded
 progs
Patch-mainline: v4.20-rc1
Git-commit: c941ce9c282cc606e6517356fcc186a9da2b4ab9
References: bsc#1109837

In preparation for BPF-to-BPF calls in offloaded programs, add a new
function attribute to the struct bpf_prog_offload_ops so that drivers
supporting eBPF offload can hook at the end of program verification, and
potentially extract information collected by the verifier.

Implement a minimal callback (returning 0) in the drivers providing the
structs, namely netdevsim and nfp.

This will be useful in the nfp driver, in later commits, to extract the
number of subprograms as well as the stack depth for those subprograms.

Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jiong Wang <jiong.wang@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/netronome/nfp/bpf/verifier.c |    8 +++++++-
 drivers/net/netdevsim/bpf.c                       |    8 +++++++-
 include/linux/bpf.h                               |    1 +
 include/linux/bpf_verifier.h                      |    1 +
 kernel/bpf/offload.c                              |   18 ++++++++++++++++++
 kernel/bpf/verifier.c                             |    3 +++
 6 files changed, 37 insertions(+), 2 deletions(-)

--- a/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
+++ b/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
@@ -640,6 +640,12 @@ nfp_verify_insn(struct bpf_verifier_env
 	return 0;
 }
 
+static int nfp_bpf_finalize(struct bpf_verifier_env *env)
+{
+	return 0;
+}
+
 const struct bpf_prog_offload_ops nfp_bpf_analyzer_ops = {
-	.insn_hook = nfp_verify_insn,
+	.insn_hook	= nfp_verify_insn,
+	.finalize	= nfp_bpf_finalize,
 };
--- a/drivers/net/netdevsim/bpf.c
+++ b/drivers/net/netdevsim/bpf.c
@@ -86,8 +86,14 @@ nsim_bpf_verify_insn(struct bpf_verifier
 	return 0;
 }
 
+static int nsim_bpf_finalize(struct bpf_verifier_env *env)
+{
+	return 0;
+}
+
 static const struct bpf_prog_offload_ops nsim_bpf_analyzer_ops = {
-	.insn_hook = nsim_bpf_verify_insn,
+	.insn_hook	= nsim_bpf_verify_insn,
+	.finalize	= nsim_bpf_finalize,
 };
 
 static bool nsim_xdp_offload_active(struct netdevsim *ns)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -253,6 +253,7 @@ struct bpf_verifier_ops {
 struct bpf_prog_offload_ops {
 	int (*insn_hook)(struct bpf_verifier_env *env,
 			 int insn_idx, int prev_insn_idx);
+	int (*finalize)(struct bpf_verifier_env *env);
 };
 
 struct bpf_prog_offload {
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -225,5 +225,6 @@ static inline struct bpf_reg_state *cur_
 int bpf_prog_offload_verifier_prep(struct bpf_verifier_env *env);
 int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env,
 				 int insn_idx, int prev_insn_idx);
+int bpf_prog_offload_finalize(struct bpf_verifier_env *env);
 
 #endif /* _LINUX_BPF_VERIFIER_H */
--- a/kernel/bpf/offload.c
+++ b/kernel/bpf/offload.c
@@ -172,6 +172,24 @@ int bpf_prog_offload_verify_insn(struct
 	return ret;
 }
 
+int bpf_prog_offload_finalize(struct bpf_verifier_env *env)
+{
+	struct bpf_prog_offload *offload;
+	int ret = -ENODEV;
+
+	down_read(&bpf_devs_lock);
+	offload = env->prog->aux->offload;
+	if (offload) {
+		if (offload->dev_ops->finalize)
+			ret = offload->dev_ops->finalize(env);
+		else
+			ret = 0;
+	}
+	up_read(&bpf_devs_lock);
+
+	return ret;
+}
+
 static void __bpf_prog_offload_destroy(struct bpf_prog *prog)
 {
 	struct bpf_prog_offload *offload = prog->aux->offload;
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5881,6 +5881,9 @@ int bpf_check(struct bpf_prog **prog, un
 		env->cur_state = NULL;
 	}
 
+	if (ret == 0 && bpf_prog_is_dev_bound(env->prog->aux))
+		ret = bpf_prog_offload_finalize(env);
+
 skip_full_check:
 	while (!pop_stack(env, NULL, NULL));
 	free_states(env);