On Fri, Nov 27, 2020 at 05:57:27PM +0000, Brendan Jackman wrote:
> 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: Brendan Jackman <jackmanb@xxxxxxxxxx>
> ---
> arch/x86/net/bpf_jit_comp.c | 39 ++++++++++++++++++++++---------------
> 1 file changed, 23 insertions(+), 16 deletions(-)
>
> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> index 94b17bd30e00..a839c1a54276 100644
> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -702,6 +702,21 @@ static void emit_modrm_dstoff(u8 **pprog, u32 r1, u32 r2, int off)
> *pprog = prog;
> }
>
> +/*
> + * Emit a REX byte if it will be necessary to address these registers
What is "REX byte" ?
May be rename it to maybe_emit_mod() ?
> + */
> +static void maybe_emit_rex(u8 **pprog, u32 reg_rm, u32 reg_reg, bool wide)
could you please keep original names as dst_reg/src_reg instead of reg_rm/reg_reg ?
reg_reg reads really odd and reg_rm is equally puzzling unless the reader studied
intel's manual. I didn't. All these new abbreviations are challenging for me.
> +{
> + u8 *prog = *pprog;
> + int cnt = 0;
> +
> + if (wide)
what is 'wide' ? Why not to call it 'bool is_alu64' ?
> + EMIT1(add_2mod(0x48, reg_rm, reg_reg));
> + else if (is_ereg(reg_rm) || is_ereg(reg_reg))
> + EMIT1(add_2mod(0x40, reg_rm, reg_reg));
> + *pprog = prog;
> +}
