[PATCH 1/2] bpf: extract SOCK_OPS_LOAD_TCP_SOCK_FIELD from SOCK_OPS_GET_FIELD

[Werner Kasselman <werner@verivus.ai>]

Extract the guarded sock_ops field load sequence out of
SOCK_OPS_GET_FIELD() into SOCK_OPS_LOAD_TCP_SOCK_FIELD(FIELD_SIZE,
FIELD_OFFSET) so callers that need a custom field offset can reuse the
same is_locked_tcp_sock guard and dst_reg == src_reg handling.

This is needed for rtt_min, which reads a minmax sub-field rather than a
direct struct member.

No functional change.

Signed-off-by: Werner Kasselman <werner@verivus.com>
---
 net/core/filter.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index fcfcb72663ca..e8ad062f63bc 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -10535,12 +10535,10 @@ static u32 sock_ops_convert_ctx_access(enum bpf_access_type type,
 	struct bpf_insn *insn = insn_buf;
 	int off;
 
-/* Helper macro for adding read access to tcp_sock or sock fields. */
-#define SOCK_OPS_GET_FIELD(BPF_FIELD, OBJ_FIELD, OBJ)			      \
+/* Helper macro for adding guarded read access to tcp_sock fields. */
+#define SOCK_OPS_LOAD_TCP_SOCK_FIELD(FIELD_SIZE, FIELD_OFFSET)		      \
 	do {								      \
 		int fullsock_reg = si->dst_reg, reg = BPF_REG_9, jmp = 2;     \
-		BUILD_BUG_ON(sizeof_field(OBJ, OBJ_FIELD) >		      \
-			     sizeof_field(struct bpf_sock_ops, BPF_FIELD));   \
 		if (si->dst_reg == reg || si->src_reg == reg)		      \
 			reg--;						      \
 		if (si->dst_reg == reg || si->src_reg == reg)		      \
@@ -10567,10 +10565,9 @@ static u32 sock_ops_convert_ctx_access(enum bpf_access_type type,
 						struct bpf_sock_ops_kern, sk),\
 				      si->dst_reg, si->src_reg,		      \
 				      offsetof(struct bpf_sock_ops_kern, sk));\
-		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(OBJ,		      \
-						       OBJ_FIELD),	      \
+		*insn++ = BPF_LDX_MEM(FIELD_SIZE,			      \
 				      si->dst_reg, si->dst_reg,		      \
-				      offsetof(OBJ, OBJ_FIELD));	      \
+				      FIELD_OFFSET);			      \
 		if (si->dst_reg == si->src_reg)	{			      \
 			*insn++ = BPF_JMP_A(2);				      \
 			*insn++ = BPF_LDX_MEM(BPF_DW, reg, si->src_reg,	      \
@@ -10580,6 +10577,14 @@ static u32 sock_ops_convert_ctx_access(enum bpf_access_type type,
 		}							      \
 	} while (0)
 
+#define SOCK_OPS_GET_FIELD(BPF_FIELD, OBJ_FIELD, OBJ)			      \
+	do {								      \
+		BUILD_BUG_ON(sizeof_field(OBJ, OBJ_FIELD) >		      \
+			     sizeof_field(struct bpf_sock_ops, BPF_FIELD));   \
+		SOCK_OPS_LOAD_TCP_SOCK_FIELD(BPF_FIELD_SIZEOF(OBJ, OBJ_FIELD),\
+					     offsetof(OBJ, OBJ_FIELD));       \
+	} while (0)
+
 #define SOCK_OPS_GET_SK()							      \
 	do {								      \
 		int fullsock_reg = si->dst_reg, reg = BPF_REG_9, jmp = 1;     \
-- 
2.43.0