| Date | Fri, 11 Sep 2020 11:44:31 +0200 | From | peterz@infradea ... | Subject | Re: [PATCH v6 5/9] kernel: Implement selective syscall userspace redirection |
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On Fri, Sep 04, 2020 at 04:31:43PM -0400, Gabriel Krisman Bertazi wrote:
> +struct syscall_user_dispatch { > + char __user *selector; > + unsigned long dispatcher_start; > + unsigned long dispatcher_end; > +};
> +int do_syscall_user_dispatch(struct pt_regs *regs) > +{ > + struct syscall_user_dispatch *sd = ¤t->syscall_dispatch; > + unsigned long ip = instruction_pointer(regs); > + char state; > + > + if (likely(ip >= sd->dispatcher_start && ip <= sd->dispatcher_end)) > + return 0;
If you use {offset,size}, instead of {start,end}, you can write the above like:
if (ip - sd->dispatcher_offset < sd->dispatcher_size) return 0;
which is just a single branch.
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