[PATCH v1 bpf-next 3/5] bpf: Add bpf_dynptr_get_size and bpf_dynptr_get_offset

[Joanne Koong <joannelkoong@gmail.com>]

bpf_dynptr_get_size returns the number of useable bytes in a dynptr and
bpf_dynptr_get_offset returns the current offset into the dynptr.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 include/linux/bpf.h      |  2 +-
 kernel/bpf/helpers.c     | 24 +++++++++++++++++++++---
 kernel/trace/bpf_trace.c |  4 ++--
 3 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 002a811b6b90..2a73ddd06e55 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1167,7 +1167,7 @@ enum bpf_dynptr_type {
 };
 
 int bpf_dynptr_check_size(u32 size);
-u32 bpf_dynptr_get_size(const struct bpf_dynptr_kern *ptr);
+u32 __bpf_dynptr_get_size(const struct bpf_dynptr_kern *ptr);
 
 #ifdef CONFIG_BPF_JIT
 int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr);
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index e4e84e92a4c6..bac4c6fe49f0 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1443,7 +1443,7 @@ static enum bpf_dynptr_type bpf_dynptr_get_type(const struct bpf_dynptr_kern *pt
 	return (ptr->size & ~(DYNPTR_RDONLY_BIT)) >> DYNPTR_TYPE_SHIFT;
 }
 
-u32 bpf_dynptr_get_size(const struct bpf_dynptr_kern *ptr)
+u32 __bpf_dynptr_get_size(const struct bpf_dynptr_kern *ptr)
 {
 	return ptr->size & DYNPTR_SIZE_MASK;
 }
@@ -1476,7 +1476,7 @@ void bpf_dynptr_set_null(struct bpf_dynptr_kern *ptr)
 
 static int bpf_dynptr_check_off_len(const struct bpf_dynptr_kern *ptr, u32 offset, u32 len)
 {
-	u32 size = bpf_dynptr_get_size(ptr);
+	u32 size = __bpf_dynptr_get_size(ptr);
 
 	if (len > size || offset > size - len)
 		return -E2BIG;
@@ -2290,7 +2290,7 @@ static int bpf_dynptr_adjust(struct bpf_dynptr_kern *ptr, u32 off_inc, u32 sz_de
 	if (!ptr->data)
 		return -EINVAL;
 
-	size = bpf_dynptr_get_size(ptr);
+	size = __bpf_dynptr_get_size(ptr);
 
 	if (sz_dec > size)
 		return -ERANGE;
@@ -2335,6 +2335,22 @@ __bpf_kfunc bool bpf_dynptr_is_rdonly(struct bpf_dynptr_kern *ptr)
 	return __bpf_dynptr_is_rdonly(ptr);
 }
 
+__bpf_kfunc __u32 bpf_dynptr_get_size(const struct bpf_dynptr_kern *ptr)
+{
+	if (!ptr->data)
+		return -EINVAL;
+
+	return __bpf_dynptr_get_size(ptr);
+}
+
+__bpf_kfunc __u32 bpf_dynptr_get_offset(const struct bpf_dynptr_kern *ptr)
+{
+	if (!ptr->data)
+		return -EINVAL;
+
+	return ptr->offset;
+}
+
 __bpf_kfunc void *bpf_cast_to_kern_ctx(void *obj)
 {
 	return obj;
@@ -2411,6 +2427,8 @@ BTF_ID_FLAGS(func, bpf_dynptr_trim)
 BTF_ID_FLAGS(func, bpf_dynptr_advance)
 BTF_ID_FLAGS(func, bpf_dynptr_is_null)
 BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly)
+BTF_ID_FLAGS(func, bpf_dynptr_get_size)
+BTF_ID_FLAGS(func, bpf_dynptr_get_offset)
 BTF_SET8_END(common_btf_ids)
 
 static const struct btf_kfunc_id_set common_kfunc_set = {
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index bcf91bc7bf71..f30bdc72d26c 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1349,9 +1349,9 @@ __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
 	}
 
 	return verify_pkcs7_signature(data_ptr->data,
-				      bpf_dynptr_get_size(data_ptr),
+				      __bpf_dynptr_get_size(data_ptr),
 				      sig_ptr->data,
-				      bpf_dynptr_get_size(sig_ptr),
+				      __bpf_dynptr_get_size(sig_ptr),
 				      trusted_keyring->key,
 				      VERIFYING_UNSPECIFIED_SIGNATURE, NULL,
 				      NULL);
-- 
2.34.1