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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon, 29 Apr 2019 13:07:33 -0700
Message-ID: <CAHk-=wg1QPz0m+7jnVcjQgkySUQLzAXE8_PZARV-vWYK27LB=w@mail.gmail.com>
Subject: Re: [PATCH 3/4] x86/ftrace: make ftrace_int3_handler() not to skip
 fops invocation
To:     Andy Lutomirski <luto@kernel.org>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Nicolai Stange <nstange@suse.de>,
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        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Jiri Kosina <jikos@kernel.org>,
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On Mon, Apr 29, 2019 at 12:24 PM Andy Lutomirski <luto@kernel.org> wrote:
> > Side note: we *already* depend on sti shadow working in other parts of the kernel, namely sti->iret.
>
> Where?  STI; IRET would be nuts.

Sorry, not 'sti;iret' but 'sti;sysexit'

> before commit 4214a16b02971c60960afd675d03544e109e0d75
>     x86/asm/entry/64/compat: Use SYSRETL to return from compat mode SYSENTER
>
> we did sti; sysxit, but, when we discussed this, I don't recall anyone
> speaking up in favor of the safely of the old code.

We still have that sti sysexit in the 32-bit code.

                     Linus