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bpf: add BPF_SIZEOF and BPF_FIELD_SIZEOF macros

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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
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12
kernel/trace/bpf_trace.c
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@@ -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;
}