skbuff: Move conditional preprocessor directives out of struct sk_buff

In preparation for using the struct_group() macro in struct sk_buff,
move the conditional preprocessor directives out of the region of struct
sk_buff that will be enclosed by struct_group(). While GCC and Clang are
happy with conditional preprocessor directives here, sparse is not, even
under -Wno-directive-within-macro[1], as would be seen under a C=1 build:

net/core/filter.c: note: in included file (through include/linux/netlink.h, include/linux/sock_diag.h):
./include/linux/skbuff.h:820:1: warning: directive in macro's argument list
./include/linux/skbuff.h:822:1: warning: directive in macro's argument list
./include/linux/skbuff.h:846:1: warning: directive in macro's argument list
./include/linux/skbuff.h:848:1: warning: directive in macro's argument list

Additionally remove empty macro argument definitions and usage.

"objdump -d" shows no object code differences.

[1] https://www.spinics.net/lists/linux-sparse/msg10857.html

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 059b626..c7889af 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -795,7 +795,7 @@ struct sk_buff {
 #else
 #define CLONED_MASK    1
 #endif
-#define CLONED_OFFSET()                offsetof(struct sk_buff, __cloned_offset)
+#define CLONED_OFFSET          offsetof(struct sk_buff, __cloned_offset)
 
        /* private: */
        __u8                    __cloned_offset[0];
@@ -818,18 +818,10 @@ struct sk_buff {
        __u32                   headers_start[0];
        /* public: */
 
-/* if you move pkt_type around you also must adapt those constants */
-#ifdef __BIG_ENDIAN_BITFIELD
-#define PKT_TYPE_MAX   (7 << 5)
-#else
-#define PKT_TYPE_MAX   7
-#endif
-#define PKT_TYPE_OFFSET()      offsetof(struct sk_buff, __pkt_type_offset)
-
        /* private: */
        __u8                    __pkt_type_offset[0];
        /* public: */
-       __u8                    pkt_type:3;
+       __u8                    pkt_type:3; /* see PKT_TYPE_MAX */
        __u8                    ignore_df:1;
        __u8                    nf_trace:1;
        __u8                    ip_summed:2;
@@ -845,16 +837,10 @@ struct sk_buff {
        __u8                    encap_hdr_csum:1;
        __u8                    csum_valid:1;
 
-#ifdef __BIG_ENDIAN_BITFIELD
-#define PKT_VLAN_PRESENT_BIT   7
-#else
-#define PKT_VLAN_PRESENT_BIT   0
-#endif
-#define PKT_VLAN_PRESENT_OFFSET()      offsetof(struct sk_buff, __pkt_vlan_present_offset)
        /* private: */
        __u8                    __pkt_vlan_present_offset[0];
        /* public: */
-       __u8                    vlan_present:1;
+       __u8                    vlan_present:1; /* See PKT_VLAN_PRESENT_BIT */
        __u8                    csum_complete_sw:1;
        __u8                    csum_level:2;
        __u8                    csum_not_inet:1;
@@ -953,6 +939,22 @@ struct sk_buff {
 #endif
 };
 
+/* if you move pkt_type around you also must adapt those constants */
+#ifdef __BIG_ENDIAN_BITFIELD
+#define PKT_TYPE_MAX   (7 << 5)
+#else
+#define PKT_TYPE_MAX   7
+#endif
+#define PKT_TYPE_OFFSET                offsetof(struct sk_buff, __pkt_type_offset)
+
+/* if you move pkt_vlan_present around you also must adapt these constants */
+#ifdef __BIG_ENDIAN_BITFIELD
+#define PKT_VLAN_PRESENT_BIT   7
+#else
+#define PKT_VLAN_PRESENT_BIT   0
+#endif
+#define PKT_VLAN_PRESENT_OFFSET        offsetof(struct sk_buff, __pkt_vlan_present_offset)
+
 #ifdef __KERNEL__
 /*
  *     Handling routines are only of interest to the kernel

diff --git a/net/core/filter.c b/net/core/filter.c
index efebbaf..8271624 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -301,7 +301,7 @@ static u32 convert_skb_access(int skb_field, int dst_reg, int src_reg,
                break;
 
        case SKF_AD_PKTTYPE:
-               *insn++ = BPF_LDX_MEM(BPF_B, dst_reg, src_reg, PKT_TYPE_OFFSET());
+               *insn++ = BPF_LDX_MEM(BPF_B, dst_reg, src_reg, PKT_TYPE_OFFSET);
                *insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg, PKT_TYPE_MAX);
 #ifdef __BIG_ENDIAN_BITFIELD
                *insn++ = BPF_ALU32_IMM(BPF_RSH, dst_reg, 5);
@@ -323,7 +323,7 @@ static u32 convert_skb_access(int skb_field, int dst_reg, int src_reg,
                                      offsetof(struct sk_buff, vlan_tci));
                break;
        case SKF_AD_VLAN_TAG_PRESENT:
-               *insn++ = BPF_LDX_MEM(BPF_B, dst_reg, src_reg, PKT_VLAN_PRESENT_OFFSET());
+               *insn++ = BPF_LDX_MEM(BPF_B, dst_reg, src_reg, PKT_VLAN_PRESENT_OFFSET);
                if (PKT_VLAN_PRESENT_BIT)
                        *insn++ = BPF_ALU32_IMM(BPF_RSH, dst_reg, PKT_VLAN_PRESENT_BIT);
                if (PKT_VLAN_PRESENT_BIT < 7)
@@ -8029,7 +8029,7 @@ static int bpf_unclone_prologue(struct bpf_insn *insn_buf, bool direct_write,
         * (Fast-path, otherwise approximation that we might be
         *  a clone, do the rest in helper.)
         */
-       *insn++ = BPF_LDX_MEM(BPF_B, BPF_REG_6, BPF_REG_1, CLONED_OFFSET());
+       *insn++ = BPF_LDX_MEM(BPF_B, BPF_REG_6, BPF_REG_1, CLONED_OFFSET);
        *insn++ = BPF_ALU32_IMM(BPF_AND, BPF_REG_6, CLONED_MASK);
        *insn++ = BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 7);
 
@@ -8617,7 +8617,7 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
        case offsetof(struct __sk_buff, pkt_type):
                *target_size = 1;
                *insn++ = BPF_LDX_MEM(BPF_B, si->dst_reg, si->src_reg,
-                                     PKT_TYPE_OFFSET());
+                                     PKT_TYPE_OFFSET);
                *insn++ = BPF_ALU32_IMM(BPF_AND, si->dst_reg, PKT_TYPE_MAX);
 #ifdef __BIG_ENDIAN_BITFIELD
                *insn++ = BPF_ALU32_IMM(BPF_RSH, si->dst_reg, 5);
@@ -8642,7 +8642,7 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
        case offsetof(struct __sk_buff, vlan_present):
                *target_size = 1;
                *insn++ = BPF_LDX_MEM(BPF_B, si->dst_reg, si->src_reg,
-                                     PKT_VLAN_PRESENT_OFFSET());
+                                     PKT_VLAN_PRESENT_OFFSET);
                if (PKT_VLAN_PRESENT_BIT)
                        *insn++ = BPF_ALU32_IMM(BPF_RSH, si->dst_reg, PKT_VLAN_PRESENT_BIT);
                if (PKT_VLAN_PRESENT_BIT < 7)