bpf: Remove prog->active check for bpf_lsm and bpf_iter

The commit 64696c40d03c ("bpf: Add __bpf_prog_{enter,exit}_struct_ops for struct_ops trampoline")
removed prog->active check for struct_ops prog.  The bpf_lsm
and bpf_iter is also using trampoline.  Like struct_ops, the bpf_lsm
and bpf_iter have fixed hooks for the prog to attach.  The
kernel does not call the same hook in a recursive way.
This patch also removes the prog->active check for
bpf_lsm and bpf_iter.

A later patch has a test to reproduce the recursion issue
for a sleepable bpf_lsm program.

This patch appends the '_recur' naming to the existing
enter and exit functions that track the prog->active counter.
New __bpf_prog_{enter,exit}[_sleepable] function are
added to skip the prog->active tracking. The '_struct_ops'
version is also removed.

It also moves the decision on picking the enter and exit function to
the new bpf_trampoline_{enter,exit}().  It returns the '_recur' ones
for all tracing progs to use.  For bpf_lsm, bpf_iter,
struct_ops (no prog->active tracking after 64696c40d03c), and
bpf_lsm_cgroup (no prog->active tracking after 69fd337a975c7),
it will return the functions that don't track the prog->active.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20221025184524.3526117-2-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 24 insertions, 15 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 9e7d46d16032..1279e699dc98 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -854,22 +854,18 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *tr, void *image, void *i
 				const struct btf_func_model *m, u32 flags,
 				struct bpf_tramp_links *tlinks,
 				void *orig_call);
-/* these two functions are called from generated trampoline */
-u64 notrace __bpf_prog_enter(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx);
-void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start, struct bpf_tramp_run_ctx *run_ctx);
-u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx);
-void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start,
-				       struct bpf_tramp_run_ctx *run_ctx);
-u64 notrace __bpf_prog_enter_lsm_cgroup(struct bpf_prog *prog,
-					struct bpf_tramp_run_ctx *run_ctx);
-void notrace __bpf_prog_exit_lsm_cgroup(struct bpf_prog *prog, u64 start,
-					struct bpf_tramp_run_ctx *run_ctx);
-u64 notrace __bpf_prog_enter_struct_ops(struct bpf_prog *prog,
-					struct bpf_tramp_run_ctx *run_ctx);
-void notrace __bpf_prog_exit_struct_ops(struct bpf_prog *prog, u64 start,
-					struct bpf_tramp_run_ctx *run_ctx);
+u64 notrace __bpf_prog_enter_sleepable_recur(struct bpf_prog *prog,
+					     struct bpf_tramp_run_ctx *run_ctx);
+void notrace __bpf_prog_exit_sleepable_recur(struct bpf_prog *prog, u64 start,
+					     struct bpf_tramp_run_ctx *run_ctx);
 void notrace __bpf_tramp_enter(struct bpf_tramp_image *tr);
 void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr);
+typedef u64 (*bpf_trampoline_enter_t)(struct bpf_prog *prog,
+				      struct bpf_tramp_run_ctx *run_ctx);
+typedef void (*bpf_trampoline_exit_t)(struct bpf_prog *prog, u64 start,
+				      struct bpf_tramp_run_ctx *run_ctx);
+bpf_trampoline_enter_t bpf_trampoline_enter(const struct bpf_prog *prog);
+bpf_trampoline_exit_t bpf_trampoline_exit(const struct bpf_prog *prog);
 
 struct bpf_ksym {
 	unsigned long		 start;
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 9e1e6965f407..1a32baa78ce2 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -642,10 +642,23 @@ static inline u32 type_flag(u32 type)
 }
 
 /* only use after check_attach_btf_id() */
-static inline enum bpf_prog_type resolve_prog_type(struct bpf_prog *prog)
+static inline enum bpf_prog_type resolve_prog_type(const struct bpf_prog *prog)
 {
 	return prog->type == BPF_PROG_TYPE_EXT ?
 		prog->aux->dst_prog->type : prog->type;
 }
 
+static inline bool bpf_prog_check_recur(const struct bpf_prog *prog)
+{
+	switch (resolve_prog_type(prog)) {
+	case BPF_PROG_TYPE_TRACING:
+		return prog->expected_attach_type != BPF_TRACE_ITER;
+	case BPF_PROG_TYPE_STRUCT_OPS:
+	case BPF_PROG_TYPE_LSM:
+		return false;
+	default:
+		return true;
+	}
+}
+
 #endif /* _LINUX_BPF_VERIFIER_H */