> On Jan 9, 2019, at 2:59 PM, Josh Poimboeuf <jpoim...@redhat.com> wrote:
>
<snip>
> +
> +void __ref arch_static_call_transform(void *site, void *tramp, void *func)
> +{
> + s32 dest_relative;
> + unsigned char opcode;
> + void *(*poker)(void *, const void *, size_t);
> + void *insn = tramp;
> +
> + mutex_lock(&text_mutex);
> +
> + /*
> + * For x86-64, a 32-bit cross-modifying write to a call destination is
> + * safe as long as it's within a cache line.
> + */
> + opcode = *(unsigned char *)insn;
> + if (opcode != 0xe8 && opcode != 0xe9) {
> + WARN_ONCE(1, "unexpected static call insn opcode 0x%x at %pS",
> + opcode, insn);
> + goto done;
> + }
> +
> + dest_relative = (long)(func) - (long)(insn + CALL_INSN_SIZE);
> +
> + poker = early_boot_irqs_disabled ? text_poke_early : text_poke;
> + poker(insn + 1, &dest_relative, sizeof(dest_relative));
> +
> +done:
> + mutex_unlock(&text_mutex);
> +}
> +EXPORT_SYMBOL_GPL(arch_static_call_transform);
Err… I was rewriting __jump_label_transform(), so if this code duplication can
be avoided, this would be great.
(See https://lkml.org/lkml/2018/11/14/72 )
