From: Andy Lutomirski <luto@kernel.org>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Borislav Petkov <bp@alien8.de>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [RFC 1/2] x86/entry/64: Use the TSS sp2 slot for rsp_scratch
Date: Mon, 23 Jul 2018 19:36:42 -0700 [thread overview]
Message-ID: <CALCETrVZHsvfXA18w2M2LKfEc6fHVEzgS-Jg9uT=k9Qw7cw69g@mail.gmail.com> (raw)
In-Reply-To: <854ac759-efec-3e35-59a9-8da35b2b5156@linux.intel.com>
On Mon, Jul 23, 2018 at 5:38 AM, Dave Hansen
<dave.hansen@linux.intel.com> wrote:
> On 07/22/2018 10:45 AM, Andy Lutomirski wrote:
>> + /*
>> + * sp2 is scratch space used by the SYSCALL64 handler. Linux does
>> + * not use rung 2, so sp2 is not otherwise needed.
>> + */
>> u64 sp2;
>
> Could we call out the actual thing that we use this slot for, and the
> symbol name so folks can find the corresponding code that does this?
> While I know the spot in entry_64 you're talking about, it might not be
> patently obvious to everyone, and it's also a bit more challenging to
> grep for than normal C code.
>
> Maybe:
>
> /*
> * Since Linux does not use ring 2, the 'sp2' slot is unused.
> * entry_SYSCALL_64 uses this as scratch space to stash the user
> * %RSP value.
> */
I'll improve this for v2.
next prev parent reply other threads:[~2018-07-24 2:37 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-22 17:45 [RFC 0/2] Get rid of the entry trampoline Andy Lutomirski
2018-07-22 17:45 ` [RFC 1/2] x86/entry/64: Use the TSS sp2 slot for rsp_scratch Andy Lutomirski
2018-07-22 20:12 ` Ingo Molnar
2018-07-23 12:38 ` Dave Hansen
2018-07-24 2:36 ` Andy Lutomirski [this message]
2018-07-22 17:45 ` [RFC 2/2] x86/pti/64: Remove the SYSCALL64 entry trampoline Andy Lutomirski
2018-07-22 18:27 ` Linus Torvalds
2018-07-22 20:59 ` Andy Lutomirski
2018-07-23 12:59 ` Dave Hansen
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