On 01/10/2018 02:51 PM, David Woodhouse wrote:
> + */
> +#define __FILL_RETURN_BUFFER(reg, sp, uniq) \
> + mov $(NUM_BRANCHES_TO_FILL/2), reg; \
> + .align 16; \
> +.Ldo_call1_ ## uniq: \
> + call .Ldo_call2_ ## uniq; \
> +.Ltrap1_ ## uniq: \
> + pause; \
> + jmp .Ltrap1_ ## uniq; \
> + .align 16; \
> +.Ldo_call2_ ## uniq: \
> + call .Ldo_loop_ ## uniq; \
> +.Ltrap2_ ## uniq: \
> + pause; \
> + jmp .Ltrap2_ ## uniq; \
> + .align 16; \
> +.Ldo_loop_ ## uniq: \
> + dec reg; \
> + jnz .Ldo_call1_ ## uniq; \
> + add $(BITS_PER_LONG/8)*NUM_BRANCHES_TO_FILL, sp;
> +
> #ifdef __ASSEMBLY__
>
> +
> + asm volatile (ALTERNATIVE("",
> + __stringify(__FILL_RETURN_BUFFER(%0, %1,
> _%=)),
> + X86_FEATURE_RETPOLINE)
We'll be patching in a fairly long set of instructions here. Maybe put
the ALTERNATIVE in the assembly and use a jmp skip_\@ for the ALTERNATIVE.
Thanks.
Tim
