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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>
This commit is contained in:
Daniel Borkmann 2016-09-09 02:45:29 +02:00 committed by David S. Miller
parent 6088b5823b
commit f035a51536
3 changed files with 27 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
include/linux/filter.h
View File

@ -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 {

12
kernel/trace/bpf_trace.c
View File

@ -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;
}

15
net/core/filter.c
View File

@ -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;