bpf, verifier: Remove redundant var_off.value ops in scalar known reg cases
In BPF_AND and BPF_OR alu cases we have this pattern when the src and dst tnum is a constant. 1 dst_reg->var_off = tnum_[op](dst_reg->var_off, src_reg.var_off) 2 scalar32_min_max_[op] 3 if (known) return 4 scalar_min_max_[op] 5 if (known) 6 __mark_reg_known(dst_reg, dst_reg->var_off.value [op] src_reg.var_off.value) The result is in 1 we calculate the var_off value and store it in the dst_reg. Then in 6 we duplicate this logic doing the op again on the value. The duplication comes from the the tnum_[op] handlers because they have already done the value calcuation. For example this is tnum_and(). struct tnum tnum_and(struct tnum a, struct tnum b) { u64 alpha, beta, v; alpha = a.value | a.mask; beta = b.value | b.mask; v = a.value & b.value; return TNUM(v, alpha & beta & ~v); } So lets remove the redundant op calculation. Its confusing for readers and unnecessary. Its also not harmful because those ops have the property, r1 & r1 = r1 and r1 | r1 = r1. Signed-off-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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kernel/bpf
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@ -5849,8 +5849,7 @@ static void scalar_min_max_and(struct bpf_reg_state *dst_reg,
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u64 umax_val = src_reg->umax_value;
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if (src_known && dst_known) {
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__mark_reg_known(dst_reg, dst_reg->var_off.value &
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src_reg->var_off.value);
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__mark_reg_known(dst_reg, dst_reg->var_off.value);
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return;
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}
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@ -5920,8 +5919,7 @@ static void scalar_min_max_or(struct bpf_reg_state *dst_reg,
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u64 umin_val = src_reg->umin_value;
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if (src_known && dst_known) {
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__mark_reg_known(dst_reg, dst_reg->var_off.value |
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src_reg->var_off.value);
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__mark_reg_known(dst_reg, dst_reg->var_off.value);
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return;
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}
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