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bpf: x86: Factor out a lookup table for some ALU opcodes 

A later commit will need to lookup a subset of these opcodes. To
avoid duplicating code, pull out a table.

The shift opcodes won't be needed by that later commit, but they're
already duplicated, so fold them into the table anyway.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210114181751.768687-4-jackmanb@google.com
This commit is contained in:
Brendan Jackman 2021-01-14 18:17:43 +00:00 committed by Alexei Starovoitov
parent 74007cfc1f
commit e5f02caccf
1 changed files with 15 additions and 18 deletions
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33
arch/x86/net/bpf_jit_comp.c
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@ -205,6 +205,18 @@ static u8 add_2reg(u8 byte, u32 dst_reg, u32 src_reg)
return byte + reg2hex[dst_reg] + (reg2hex[src_reg] << 3);
}
/* Some 1-byte opcodes for binary ALU operations */
static u8 simple_alu_opcodes[] = {
[BPF_ADD] = 0x01,
[BPF_SUB] = 0x29,
[BPF_AND] = 0x21,
[BPF_OR] = 0x09,
[BPF_XOR] = 0x31,
[BPF_LSH] = 0xE0,
[BPF_RSH] = 0xE8,
[BPF_ARSH] = 0xF8,
};
static void jit_fill_hole(void *area, unsigned int size)
{
/* Fill whole space with INT3 instructions */
@ -862,15 +874,9 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
case BPF_ALU64 | BPF_AND | BPF_X:
case BPF_ALU64 | BPF_OR | BPF_X:
case BPF_ALU64 | BPF_XOR | BPF_X:
switch (BPF_OP(insn->code)) {
case BPF_ADD: b2 = 0x01; break;
case BPF_SUB: b2 = 0x29; break;
case BPF_AND: b2 = 0x21; break;
case BPF_OR: b2 = 0x09; break;
case BPF_XOR: b2 = 0x31; break;
}
maybe_emit_mod(&prog, dst_reg, src_reg,
BPF_CLASS(insn->code) == BPF_ALU64);
b2 = simple_alu_opcodes[BPF_OP(insn->code)];
EMIT2(b2, add_2reg(0xC0, dst_reg, src_reg));
break;
@ -1050,12 +1056,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
else if (is_ereg(dst_reg))
EMIT1(add_1mod(0x40, dst_reg));
switch (BPF_OP(insn->code)) {
case BPF_LSH: b3 = 0xE0; break;
case BPF_RSH: b3 = 0xE8; break;
case BPF_ARSH: b3 = 0xF8; break;
}
b3 = simple_alu_opcodes[BPF_OP(insn->code)];
if (imm32 == 1)
EMIT2(0xD1, add_1reg(b3, dst_reg));
else
@ -1089,11 +1090,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
else if (is_ereg(dst_reg))
EMIT1(add_1mod(0x40, dst_reg));
switch (BPF_OP(insn->code)) {
case BPF_LSH: b3 = 0xE0; break;
case BPF_RSH: b3 = 0xE8; break;
case BPF_ARSH: b3 = 0xF8; break;
}
b3 = simple_alu_opcodes[BPF_OP(insn->code)];
EMIT2(0xD3, add_1reg(b3, dst_reg));
if (src_reg != BPF_REG_4)