linux-kernel - Re: [PATCH v3 0/6] Static calls

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: <CCF7D3C7-9D12-489B-B778-C2156D2DBF47@vmware.com>
Date:   Fri, 11 Jan 2019 17:23:03 +0000
From:   Nadav Amit <namit@...are.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
CC:     Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jason Baron <jbaron@...mai.com>, Jiri Kosina <jkosina@...e.cz>,
        David Laight <David.Laight@...lab.com>,
        Borislav Petkov <bp@...en8.de>,
        Julia Cartwright <julia@...com>, Jessica Yu <jeyu@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Edward Cree <ecree@...arflare.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: Re: [PATCH v3 0/6] Static calls

> On Jan 11, 2019, at 8:07 AM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> 
> On Fri, Jan 11, 2019 at 03:48:59PM +0000, Nadav Amit wrote:
>>> I liked the idea, BUT, how would it work for callee-saved PV ops?  In
>>> that case there's only one clobbered register to work with (rax).
>> 
>> That’s would be more tricky. How about using a per-CPU trampoline code to
>> hold a direct call to the target and temporarily disable preemption (which
>> might be simpler by disabling IRQs):
>> 

Allow me to simplify/correct:

>> Static-call modifier:
>> 
>>        1. synchronize_sched() to ensure per-cpu trampoline is not used
No need for (1) (We are going to sync using IPI).

>> 	2. Patches the jmp in a per-cpu trampoline (see below)
>> 	3. Saves the call source RIP in [per-cpu scratchpad RIP] (below)
Both do not need to be per-cpu

>> 	4. Configures the int3 handler to use static-call int3 handler
>> 	5. Patches the call target (as it currently does).
Note that text_poke_bp() would do eventually:

	on_each_cpu(do_sync_core, NULL, 1);

So you should know no cores run the trampoline after (5).