linux-kernel - Re: [PATCH v3 1/6] x86/alternatives: Teach text_poke

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Message-ID: <20191008110412.29afac9f@gandalf.local.home>
Date:   Tue, 8 Oct 2019 11:04:12 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, mhiramat@...nel.org,
        bristot@...hat.com, jbaron@...mai.com,
        torvalds@...ux-foundation.org, tglx@...utronix.de,
        mingo@...nel.org, namit@...are.com, hpa@...or.com, luto@...nel.org,
        ard.biesheuvel@...aro.org, jpoimboe@...hat.com
Subject: Re: [PATCH v3 1/6] x86/alternatives: Teach text_poke_bp() to
 emulate instructions

On Tue, 8 Oct 2019 16:54:24 +0200
Borislav Petkov <bp@...en8.de> wrote:

> On Tue, Oct 08, 2019 at 04:48:34PM +0200, Peter Zijlstra wrote:
> > Can, but why? That's more lines for no raisin ;-)  
> 
> Here's a raisin: I was looking at this and then all of a sudden went:
> "W00t, why is this do_sync part of the loop at all? Do they belong
> together? Nope."
> 

But it is part of the loop...


+	for (do_sync = 0, i = 0; i < nr_entries; i++) {
+		if (tp[i].text[0] == INT3_INSN_OPCODE)
+			continue;
+
+		text_poke(tp[i].addr, tp[i].text, sizeof(int3));
+		do_sync++;
+	}
+

The difference between do_sync and i is that i gets incremented at
every iteration, where do_sync gets incremented only when the first
conditional is false. But I still see do_sync as a loop variable.

-- Steve