Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Fri, 5 Oct 2018 22:02:20 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     linux-kernel@vger.kernel.org
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Ingo Molnar <mingo@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Matthew Helsley <mhelsley@vmware.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        David Woodhouse <dwmw2@infradead.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Jason Baron <jbaron@akamai.com>, Jiri Kosina <jkosina@suse.cz>
Subject: Re: [POC][RFC][PATCH 1/2] jump_function: Addition of new feature
 "jump_function"
Message-ID: <20181005220220.770d9e18@vmware.local.home>
In-Reply-To: <20181006015720.634688468@goodmis.org>
References: <20181006015110.653946300@goodmis.org>
        <20181006015720.634688468@goodmis.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, 05 Oct 2018 21:51:11 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> +#define arch_dynfunc_trampoline(name, def)	\
> +	asm volatile (				\
> +	".globl dynfunc_" #name "; \n\t"	\
> +	"dynfunc_" #name ": \n\t"		\
> +	"jmp " #def " \n\t"			\
> +	".balign 8 \n \t"			\
> +	: : : "memory" )
> +

Note, the assembler can easily put in a two byte jump here. The .balign
was suppose to also have some padding (nop) incase that happens. It's
fine, because we can just replace it with a 5 byte jump, as long as we
have 3 bytes afterward if it is a two byte jump.

-- Steve