Commit 74007cfc authored by Brendan Jackman's avatar Brendan Jackman Committed by Alexei Starovoitov

bpf: x86: Factor out emission of REX byte

The JIT case for encoding atomic ops is about to get more
complicated. In order to make the review & resulting code easier,
let's factor out some shared helpers.
Signed-off-by: default avatarBrendan Jackman <jackmanb@google.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210114181751.768687-3-jackmanb@google.com
parent 11c11d07
......@@ -702,6 +702,21 @@ static void emit_insn_suffix(u8 **pprog, u32 ptr_reg, u32 val_reg, int off)
*pprog = prog;
}
/*
* Emit a REX byte if it will be necessary to address these registers
*/
static void maybe_emit_mod(u8 **pprog, u32 dst_reg, u32 src_reg, bool is64)
{
u8 *prog = *pprog;
int cnt = 0;
if (is64)
EMIT1(add_2mod(0x48, dst_reg, src_reg));
else if (is_ereg(dst_reg) || is_ereg(src_reg))
EMIT1(add_2mod(0x40, dst_reg, src_reg));
*pprog = prog;
}
/* LDX: dst_reg = *(u8*)(src_reg + off) */
static void emit_ldx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off)
{
......@@ -854,10 +869,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
case BPF_OR: b2 = 0x09; break;
case BPF_XOR: b2 = 0x31; break;
}
if (BPF_CLASS(insn->code) == BPF_ALU64)
EMIT1(add_2mod(0x48, dst_reg, src_reg));
else if (is_ereg(dst_reg) || is_ereg(src_reg))
EMIT1(add_2mod(0x40, dst_reg, src_reg));
maybe_emit_mod(&prog, dst_reg, src_reg,
BPF_CLASS(insn->code) == BPF_ALU64);
EMIT2(b2, add_2reg(0xC0, dst_reg, src_reg));
break;
......@@ -1302,20 +1315,16 @@ st: if (is_imm8(insn->off))
case BPF_JMP32 | BPF_JSGE | BPF_X:
case BPF_JMP32 | BPF_JSLE | BPF_X:
/* cmp dst_reg, src_reg */
if (BPF_CLASS(insn->code) == BPF_JMP)
EMIT1(add_2mod(0x48, dst_reg, src_reg));
else if (is_ereg(dst_reg) || is_ereg(src_reg))
EMIT1(add_2mod(0x40, dst_reg, src_reg));
maybe_emit_mod(&prog, dst_reg, src_reg,
BPF_CLASS(insn->code) == BPF_JMP);
EMIT2(0x39, add_2reg(0xC0, dst_reg, src_reg));
goto emit_cond_jmp;
case BPF_JMP | BPF_JSET | BPF_X:
case BPF_JMP32 | BPF_JSET | BPF_X:
/* test dst_reg, src_reg */
if (BPF_CLASS(insn->code) == BPF_JMP)
EMIT1(add_2mod(0x48, dst_reg, src_reg));
else if (is_ereg(dst_reg) || is_ereg(src_reg))
EMIT1(add_2mod(0x40, dst_reg, src_reg));
maybe_emit_mod(&prog, dst_reg, src_reg,
BPF_CLASS(insn->code) == BPF_JMP);
EMIT2(0x85, add_2reg(0xC0, dst_reg, src_reg));
goto emit_cond_jmp;
......@@ -1351,10 +1360,8 @@ st: if (is_imm8(insn->off))
case BPF_JMP32 | BPF_JSLE | BPF_K:
/* test dst_reg, dst_reg to save one extra byte */
if (imm32 == 0) {
if (BPF_CLASS(insn->code) == BPF_JMP)
EMIT1(add_2mod(0x48, dst_reg, dst_reg));
else if (is_ereg(dst_reg))
EMIT1(add_2mod(0x40, dst_reg, dst_reg));
maybe_emit_mod(&prog, dst_reg, dst_reg,
BPF_CLASS(insn->code) == BPF_JMP);
EMIT2(0x85, add_2reg(0xC0, dst_reg, dst_reg));
goto emit_cond_jmp;
}
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment