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    Subject[PATCH v2 bpf-next 03/13] bpf: x86: Factor out function to emit NEG
    From
    There's currently only one usage of this but implementation of
    atomic_sub add another.

    Signed-off-by: Brendan Jackman <jackmanb@google.com>
    ---
    arch/x86/net/bpf_jit_comp.c | 23 ++++++++++++++++++-----
    1 file changed, 18 insertions(+), 5 deletions(-)

    diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
    index a839c1a54276..49dea0c1a130 100644
    --- a/arch/x86/net/bpf_jit_comp.c
    +++ b/arch/x86/net/bpf_jit_comp.c
    @@ -783,6 +783,22 @@ static void emit_stx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off)
    *pprog = prog;
    }

    +
    +static void emit_neg(u8 **pprog, u32 reg, bool is64)
    +{
    + u8 *prog = *pprog;
    + int cnt = 0;
    +
    + /* Emit REX byte if necessary */
    + if (is64)
    + EMIT1(add_1mod(0x48, reg));
    + else if (is_ereg(reg))
    + EMIT1(add_1mod(0x40, reg));
    +
    + EMIT2(0xF7, add_1reg(0xD8, reg)); /* x86 NEG */
    + *pprog = prog;
    +}
    +
    static bool ex_handler_bpf(const struct exception_table_entry *x,
    struct pt_regs *regs, int trapnr,
    unsigned long error_code, unsigned long fault_addr)
    @@ -884,11 +900,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
    /* neg dst */
    case BPF_ALU | BPF_NEG:
    case BPF_ALU64 | BPF_NEG:
    - if (BPF_CLASS(insn->code) == BPF_ALU64)
    - EMIT1(add_1mod(0x48, dst_reg));
    - else if (is_ereg(dst_reg))
    - EMIT1(add_1mod(0x40, dst_reg));
    - EMIT2(0xF7, add_1reg(0xD8, dst_reg));
    + emit_neg(&prog, dst_reg,
    + BPF_CLASS(insn->code) == BPF_ALU64);
    break;

    case BPF_ALU | BPF_ADD | BPF_K:
    --
    2.29.2.454.gaff20da3a2-goog
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