linux-kernel - Re: [PATCH v2] x86/asm: Pad assembly functions with INT3 instructions

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Message-ID: <CA+55aFySWuQvnJ=27GUbz+h=Jop6F2TYFqnALAaeXXiPivLtqQ@mail.gmail.com>
Date:   Tue, 15 May 2018 16:28:58 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Alexey Dobriyan <adobriyan@...il.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Anvin <h.peter.anvin@...el.com>,
        kernel test robot <xiaolong.ye@...el.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Peter Anvin <hpa@...or.com>, tipbuild@...or.com,
        LKP <lkp@...org>, "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [PATCH v2] x86/asm: Pad assembly functions with INT3 instructions

On Tue, May 15, 2018 at 3:58 PM Alexey Dobriyan <adobriyan@...il.com> wrote:
>          jb      resume_kernel                   # not returning to v8086
or userspace
> -
> -ENTRY(resume_userspace)

I went back in history, and we used to have multiple "jmp resume_userspace"
including even the vm86.c code (in a different file) doing that, so there
*used* to be a reason for this being a global symbol (and yes, we had a
fall-through to that global symbol even in those days).

That said, I also look at "resume_kernel". There's no reason to make that
globally visible afaik. It looks local to entry_32.S, and should look like
restore_all rather than resume_userspace.

So we probably should remove the ENTRY() for that too, and just make it be

          ALIGN
         resume_kernel:

instead?

I guess the reason for removing that other ENTRY() is different from this
case, though..

                Linus