linux-kernel - Re: [PATCH 3/3 v5] livepatch: Use the default ftrace_ops instead of REGS when ARGS is available

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Message-ID: <20201112113939.GU2651@hirez.programming.kicks-ass.net>
Date:   Thu, 12 Nov 2020 12:39:39 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Thomas Gleixner <tglx@...utronix.de>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>, live-patching@...r.kernel.org
Subject: Re: [PATCH 3/3 v5] livepatch: Use the default ftrace_ops instead of
 REGS when ARGS is available

On Thu, Nov 12, 2020 at 09:21:44AM +0100, Peter Zijlstra wrote:
> Also, do you want something like:
> 
> unsigned long ftrace_regs_get_register(struct ftrace_regs *regs, unsigned int offset)
> {

I forgot the full regs case:

	if (regs->regs.cs)
		return regs_get_register(regs->regs, offset);

> 	switch (offset / sizeof(long)) {
> 	case  4: /* RBP */
> 
> 	case  8: /* R9  */
> 	case  9: /* R8  */
> 	case 10: /* RAX */
> 	case 11: /* RCX */
> 	case 12: /* RDX */
> 	case 13: /* RSI */
> 	case 14: /* RDI */
> 	case 15: /* ORIG_RAX */
> 	case 16: /* RIP */
> 		return *(unsigned long *)regs->regs + offset;
> 
> 	default:
> 		WARN_ON_ONCE(1);
> 	}
> 	return 0;
> }