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skbuff: Move conditional preprocessor directives out of struct sk_buff

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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>
This commit is contained in:
Kees Cook 2021-11-20 16:31:48 -08:00 committed by David S. Miller
parent cb902b332f
commit fba84957e2
2 changed files with 24 additions and 22 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

36
include/linux/skbuff.h
View file

@ -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

10
net/core/filter.c
View file

@ -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)