linux-kernel - Re: [RFC][PATCH] ftrace/x86: Emulate call function while updating in breakpoint handler

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190501190348.GT7905@worktop.programming.kicks-ass.net>
Date:   Wed, 1 May 2019 21:03:48 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Nicolai Stange <nstange@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Shuah Khan <shuah@...nel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Juergen Gross <jgross@...e.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nayna Jain <nayna@...ux.ibm.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Joerg Roedel <jroedel@...e.de>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        live-patching@...r.kernel.org,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>
Subject: Re: [RFC][PATCH] ftrace/x86: Emulate call function while updating in
 breakpoint handler

On Wed, May 01, 2019 at 02:58:24PM -0400, Steven Rostedt wrote:
> > +	if (ftrace_location(ip)) {
> > +		int3_emulate_call(regs, ftrace_update_func_call);
> 
> Should be:
> 
> 		int3_emulate_call(regs, (unsigned long)ftrace_regs_caller);

Ah, I lost the plot a little there.

> > +		return 1;
> > +	} else if (is_ftrace_caller(ip)) {
> > +		if (!ftrace_update_func_call) {
> > +			int3_emulate_jmp(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE);
> 
> I see what you did here, but I think:
> 
> 			int3_emulate_jmp(regs, ip + CALL_INSN_SIZE);
> 
> looks better. But that said, we could in the beginning do:
> 
> 	ip = regs->ip - INT3_INSN_SIZE;
> 
> instead of
> 
> 	ip = regs->ip - 1;
> 
> I made these updates and posted them to Linus.

I was actually considering:

static inline void int3_emulate_nop(struct pt_regs *regs, unsigned long size)
{
	int3_emulate_jmp(regs, regs->ip - INT3_INSN_SIZE + size);
}

And then the above becomes:

	int3_emulate_nop(regs, CALL_INSN_SIZE);

Hmm?