bpf: add BPF_SIZEOF and BPF_FIELD_SIZEOF macros

Add BPF_SIZEOF() and BPF_FIELD_SIZEOF() macros to improve the code a bit
which otherwise often result in overly long bytes_to_bpf_size(sizeof())
and bytes_to_bpf_size(FIELD_SIZEOF()) lines. So place them into a macro
helper instead. Moreover, we currently have a BUILD_BUG_ON(BPF_FIELD_SIZEOF())
check in convert_bpf_extensions(), but we should rather make that generic
as well and add a BUILD_BUG_ON() test in all BPF_SIZEOF()/BPF_FIELD_SIZEOF()
users to detect any rewriter size issues at compile time. Note, there are
currently none, but we want to assert that it stays this way.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/filter.h b/include/linux/filter.h
index a16439b..7fabad8 100644 (file)
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -314,6 +314,20 @@ struct bpf_prog_aux;
        bpf_size;                                               \
 })
 
+#define BPF_SIZEOF(type)                                       \
+       ({                                                      \
+               const int __size = bytes_to_bpf_size(sizeof(type)); \
+               BUILD_BUG_ON(__size < 0);                       \
+               __size;                                         \
+       })
+
+#define BPF_FIELD_SIZEOF(type, field)                          \
+       ({                                                      \
+               const int __size = bytes_to_bpf_size(FIELD_SIZEOF(type, field)); \
+               BUILD_BUG_ON(__size < 0);                       \
+               __size;                                         \
+       })
+
 #ifdef CONFIG_COMPAT
 /* A struct sock_filter is architecture independent. */
 struct compat_sock_fprog {

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index d3869b0..e63d7d4 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -583,18 +583,18 @@ static u32 pe_prog_convert_ctx_access(enum bpf_access_type type, int dst_reg,
        switch (ctx_off) {
        case offsetof(struct bpf_perf_event_data, sample_period):
                BUILD_BUG_ON(FIELD_SIZEOF(struct perf_sample_data, period) != sizeof(u64));
-               *insn++ = BPF_LDX_MEM(bytes_to_bpf_size(FIELD_SIZEOF(struct bpf_perf_event_data_kern, data)),
-                                     dst_reg, src_reg,
+
+               *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_perf_event_data_kern,
+                                                      data), dst_reg, src_reg,
                                      offsetof(struct bpf_perf_event_data_kern, data));
                *insn++ = BPF_LDX_MEM(BPF_DW, dst_reg, dst_reg,
                                      offsetof(struct perf_sample_data, period));
                break;
        default:
-               *insn++ = BPF_LDX_MEM(bytes_to_bpf_size(FIELD_SIZEOF(struct bpf_perf_event_data_kern, regs)),
-                                     dst_reg, src_reg,
+               *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_perf_event_data_kern,
+                                                      regs), dst_reg, src_reg,
                                      offsetof(struct bpf_perf_event_data_kern, regs));
-               *insn++ = BPF_LDX_MEM(bytes_to_bpf_size(sizeof(long)),
-                                     dst_reg, dst_reg, ctx_off);
+               *insn++ = BPF_LDX_MEM(BPF_SIZEOF(long), dst_reg, dst_reg, ctx_off);
                break;
        }
 

diff --git a/net/core/filter.c b/net/core/filter.c
index 628ed8c..120c813 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -233,9 +233,8 @@ static bool convert_bpf_extensions(struct sock_filter *fp,
        case SKF_AD_OFF + SKF_AD_HATYPE:
                BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, ifindex) != 4);
                BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, type) != 2);
-               BUILD_BUG_ON(bytes_to_bpf_size(FIELD_SIZEOF(struct sk_buff, dev)) < 0);
 
-               *insn++ = BPF_LDX_MEM(bytes_to_bpf_size(FIELD_SIZEOF(struct sk_buff, dev)),
+               *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, dev),
                                      BPF_REG_TMP, BPF_REG_CTX,
                                      offsetof(struct sk_buff, dev));
                /* if (tmp != 0) goto pc + 1 */
@@ -2685,7 +2684,7 @@ static u32 bpf_net_convert_ctx_access(enum bpf_access_type type, int dst_reg,
        case offsetof(struct __sk_buff, ifindex):
                BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, ifindex) != 4);
 
-               *insn++ = BPF_LDX_MEM(bytes_to_bpf_size(FIELD_SIZEOF(struct sk_buff, dev)),
+               *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, dev),
                                      dst_reg, src_reg,
                                      offsetof(struct sk_buff, dev));
                *insn++ = BPF_JMP_IMM(BPF_JEQ, dst_reg, 0, 1);
@@ -2750,7 +2749,7 @@ static u32 bpf_net_convert_ctx_access(enum bpf_access_type type, int dst_reg,
                break;
 
        case offsetof(struct __sk_buff, data):
-               *insn++ = BPF_LDX_MEM(bytes_to_bpf_size(FIELD_SIZEOF(struct sk_buff, data)),
+               *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, data),
                                      dst_reg, src_reg,
                                      offsetof(struct sk_buff, data));
                break;
@@ -2759,8 +2758,8 @@ static u32 bpf_net_convert_ctx_access(enum bpf_access_type type, int dst_reg,
                ctx_off -= offsetof(struct __sk_buff, data_end);
                ctx_off += offsetof(struct sk_buff, cb);
                ctx_off += offsetof(struct bpf_skb_data_end, data_end);
-               *insn++ = BPF_LDX_MEM(bytes_to_bpf_size(sizeof(void *)),
-                                     dst_reg, src_reg, ctx_off);
+               *insn++ = BPF_LDX_MEM(BPF_SIZEOF(void *), dst_reg, src_reg,
+                                     ctx_off);
                break;
 
        case offsetof(struct __sk_buff, tc_index):
@@ -2795,12 +2794,12 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type, int dst_reg,
 
        switch (ctx_off) {
        case offsetof(struct xdp_md, data):
-               *insn++ = BPF_LDX_MEM(bytes_to_bpf_size(FIELD_SIZEOF(struct xdp_buff, data)),
+               *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct xdp_buff, data),
                                      dst_reg, src_reg,
                                      offsetof(struct xdp_buff, data));
                break;
        case offsetof(struct xdp_md, data_end):
-               *insn++ = BPF_LDX_MEM(bytes_to_bpf_size(FIELD_SIZEOF(struct xdp_buff, data_end)),
+               *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct xdp_buff, data_end),
                                      dst_reg, src_reg,
                                      offsetof(struct xdp_buff, data_end));
                break;