Re: [PATCH v11 2/9] btf: Handle dynamic pointer parameter in kfuncs

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On 8/12/22 12:18 PM, Roberto Sassu wrote:
Allow the bpf_dynptr_kern parameter to be specified in kfuncs. Also, ensure
that the dynamic pointer is valid and initialized.

Cc: Joanne Koong <joannelkoong@xxxxxxxxx>
Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
  include/linux/bpf_verifier.h |  3 +++
  kernel/bpf/btf.c             | 22 ++++++++++++++++++++++
  kernel/bpf/verifier.c        |  4 ++--
  3 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 2e3bad8640dc..55876fbdbae2 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -560,6 +560,9 @@ int check_kfunc_mem_size_reg(struct bpf_verifier_env *env, struct bpf_reg_state
  			     u32 regno);
  int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
  		   u32 regno, u32 mem_size);
+bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env,
+			      struct bpf_reg_state *reg,
+			      enum bpf_arg_type arg_type);
/* this lives here instead of in bpf.h because it needs to dereference tgt_prog */
  static inline u64 bpf_trampoline_compute_key(const struct bpf_prog *tgt_prog,
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index e49b3b6d48ad..86e63f2ee5da 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -195,6 +195,10 @@
  	     i < btf_type_vlen(struct_type);					\
  	     i++, member++)
+#define stringify_struct(x) \
+	({ BUILD_BUG_ON(sizeof(struct x) < 0);	\
+	   __stringify(x); })
+

I'd say lets move this to include/linux/btf.h with a comment explaining the BUILD_BUG_ON()
which ensures the struct actually exits.

If there's ever use outside of BTF, it could be relocated to include/linux/stringify.h.

  DEFINE_IDR(btf_idr);
  DEFINE_SPINLOCK(btf_idr_lock);



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