From: Dave Hansen <dave.hansen@intel.com>
To: Brian Gerst <brgerst@gmail.com>, Andy Lutomirski <luto@kernel.org>
Cc: X86 ML <x86@kernel.org>, Borislav Petkov <bpetkov@suse.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 03/18] x86/asm/64: Move SWAPGS into the common iret-to-usermode path
Date: Thu, 26 Oct 2017 07:13:32 -0700 [thread overview]
Message-ID: <ff342ae6-67ef-370d-5c84-19cd0ed69711@intel.com> (raw)
In-Reply-To: <CAMzpN2hOinVAVpk15HzEz92TLw=S6U3Ji-dmmdgkh3TDMRbjYw@mail.gmail.com>
On 10/26/2017 06:52 AM, Brian Gerst wrote:
> On Thu, Oct 26, 2017 at 4:26 AM, Andy Lutomirski <luto@kernel.org> wrote:
>> All of the code paths that ended up doing IRET to usermode did
>> SWAPGS immediately beforehand. Move the SWAPGS into the common
>> code.
>>
>> Signed-off-by: Andy Lutomirski <luto@kernel.org>
>
>> +GLOBAL(swapgs_restore_regs_and_return_to_usermode)
>
> Is adding swapgs to the label really necessary? It's redundant with
> the usermode part. I'm noticing a trend towards absurdly verbose
> labels lately.
I kinda appreciate the verbosity. When I see a jump to such a label, I
know explicitly what the jumper has to do. While it's possible that
every "return to usermode" spot in the kernel does a swapgs, it's not
patently obvious to me that every last one does that in every last
situation.
There are also places where we do register restoring after swapgs and
then return to userspace. It's nice to know what mode we are in and
what we are supposed to to just from the label.
next prev parent reply other threads:[~2017-10-26 14:14 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-26 8:26 [PATCH 00/18] Pile o' entry/exit/sp0 changes Andy Lutomirski
2017-10-26 8:26 ` [PATCH 01/18] x86/asm/64: Remove the restore_c_regs_and_iret label Andy Lutomirski
2017-10-26 15:07 ` Borislav Petkov
2017-11-10 6:08 ` [01/18] " kemi
2017-10-26 8:26 ` [PATCH 02/18] x86/asm/64: Split the iret-to-user and iret-to-kernel paths Andy Lutomirski
2017-10-27 18:05 ` Dave Hansen
2017-11-01 11:34 ` Andy Lutomirski
2017-10-27 20:04 ` Borislav Petkov
2017-11-01 11:32 ` Andy Lutomirski
2017-10-26 8:26 ` [PATCH 03/18] x86/asm/64: Move SWAPGS into the common iret-to-usermode path Andy Lutomirski
2017-10-26 13:52 ` Brian Gerst
2017-10-26 14:13 ` Dave Hansen [this message]
2017-10-26 14:28 ` Borislav Petkov
2017-10-27 15:44 ` Andy Lutomirski
2017-10-27 18:08 ` Dave Hansen
2017-10-26 8:26 ` [PATCH 04/18] x86/asm/64: Simplify reg restore code in the standard IRET paths Andy Lutomirski
2017-10-26 8:26 ` [PATCH 05/18] x86/asm/64: Shrink paranoid_exit_restore and make labels local Andy Lutomirski
2017-10-27 20:07 ` Borislav Petkov
2017-10-26 8:26 ` [PATCH 06/18] x86/asm/64: Use pop instead of movq in syscall_return_via_sysret Andy Lutomirski
2017-10-27 20:11 ` Borislav Petkov
2017-10-26 8:26 ` [PATCH 07/18] x86/asm/64: Merge the fast and slow SYSRET paths Andy Lutomirski
2017-10-27 20:11 ` Borislav Petkov
2017-11-01 11:29 ` Andy Lutomirski
2017-11-01 12:35 ` Borislav Petkov
2017-11-01 17:26 ` Thomas Gleixner
2017-11-01 17:25 ` Brian Gerst
2017-11-01 20:35 ` Andy Lutomirski
2017-10-26 8:26 ` [PATCH 08/18] xen: add xen nmi trap entry Andy Lutomirski
2017-10-26 8:26 ` [PATCH 09/18] x86/asm/64: De-Xen-ify our NMI code Andy Lutomirski
2017-10-26 8:41 ` Juergen Gross
2017-10-27 20:11 ` Borislav Petkov
2017-10-26 8:26 ` [PATCH 10/18] x86/asm/32: Pull MSR_IA32_SYSENTER_CS update code out of native_load_sp0() Andy Lutomirski
2017-10-26 18:00 ` Brian Gerst
2017-10-27 13:51 ` Thomas Gleixner
2017-10-27 15:50 ` Andy Lutomirski
2017-10-27 20:11 ` Borislav Petkov
2017-10-26 8:26 ` [PATCH 11/18] x86/asm/64: Pass sp0 directly to load_sp0() Andy Lutomirski
2017-10-27 20:12 ` Borislav Petkov
2017-10-26 8:26 ` [PATCH 12/18] x86/asm: Add task_top_of_stack() to find the top of a task's stack Andy Lutomirski
2017-10-26 8:26 ` [PATCH 13/18] x86/xen/64: Clean up SP code in cpu_initialize_context() Andy Lutomirski
2017-10-26 8:43 ` Juergen Gross
2017-10-26 8:26 ` [PATCH 14/18] x86/boot/64: Stop initializing TSS.sp0 at boot Andy Lutomirski
2017-10-27 18:21 ` Dave Hansen
2017-10-28 8:10 ` Andy Lutomirski
2017-10-26 8:26 ` [PATCH 15/18] x86/asm/64: Remove all remaining direct thread_struct::sp0 reads Andy Lutomirski
2017-11-01 10:08 ` Borislav Petkov
2017-10-26 8:26 ` [PATCH 16/18] x86/boot/32: Fix cpu_current_top_of_stack initialization at boot Andy Lutomirski
2017-11-01 10:18 ` Borislav Petkov
2017-10-26 8:26 ` [PATCH 17/18] x86/asm/64: Remove thread_struct::sp0 Andy Lutomirski
2017-10-28 0:52 ` Brian Gerst
2017-11-01 10:23 ` Borislav Petkov
2017-11-01 10:40 ` Andy Lutomirski
2017-10-26 8:26 ` [PATCH 18/18] x86/traps: Use a new on_thread_stack() helper to clean up an assertion Andy Lutomirski
2017-11-01 10:31 ` Borislav Petkov
2017-11-01 10:45 ` Andy Lutomirski
2017-10-26 15:55 ` [PATCH 00/18] Pile o' entry/exit/sp0 changes Linus Torvalds
2017-10-28 7:31 ` Andy Lutomirski
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