linux-kernel - [PATCH V3 0/6] x86: don't abuse tss.sp1

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Date:   Thu, 28 Jan 2021 00:32:16 +0800
From:   Lai Jiangshan <jiangshanlai@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Lai Jiangshan <laijs@...ux.alibaba.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Joerg Roedel <jroedel@...e.de>,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        Kees Cook <keescook@...omium.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Jens Axboe <axboe@...nel.dk>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Brian Gerst <brgerst@...il.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Mike Rapoport <rppt@...nel.org>, Mike Hommey <mh@...ndium.org>,
        Mark Gross <mgross@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Anthony Steinhauser <asteinhauser@...gle.com>,
        Jay Lang <jaytlang@....edu>,
        "Chang S. Bae" <chang.seok.bae@...el.com>
Subject: [PATCH V3 0/6] x86: don't abuse tss.sp1

From: Lai Jiangshan <laijs@...ux.alibaba.com>

In x86_64, tss.sp1 is reused as cpu_current_top_of_stack.  But we can
directly use percpu since CR3 and gs_base is correct when it is used.

In x86_32, tss.sp1 is resued as thread.sp0 in three places in entry
code.  We have the correct CR3 and %fs at two of the places.  The last
one is sysenter.  This patchset makes %fs available earlier so that
we can also use percpu in sysenter.  And add a percpu cpu_current_thread_sp0
for thread.sp0 instead of tss.sp1

[V2]: https://lore.kernel.org/lkml/20210125173444.22696-1-jiangshanlai@gmail.com/
[V1]: https://lore.kernel.org/lkml/20210123084900.3118-1-jiangshanlai@gmail.com/

Changed from V2
	Add missing "%ss:" reported by Brian Gerst.

Changed from V1
	Requested from Andy to also fix sp1 for x86_32.
	Update comments in the x86_64 patch as Andy sugguested.

Lai Jiangshan (6):
  x86_64: move cpu_current_top_of_stack out of TSS
  x86_32: use percpu instead of offset-calculation to get thread.sp0
    when SWITCH_TO_KERNEL_STACK
  x86_32/sysenter: switch to the task stack without emptying the entry
    stack
  x86_32/sysenter: restore %fs before switching stack
  x86_32/sysenter: use percpu to get thread.sp0 when sysenter
  x86_32: use cpu_current_thread_sp0 instead of cpu_tss_rw.x86_tss.sp1

 arch/x86/entry/entry_32.S          | 38 +++++++++++++++++-------------
 arch/x86/include/asm/processor.h   | 12 ++--------
 arch/x86/include/asm/switch_to.h   |  9 ++-----
 arch/x86/include/asm/thread_info.h |  6 -----
 arch/x86/kernel/asm-offsets.c      |  1 -
 arch/x86/kernel/asm-offsets_32.c   | 10 --------
 arch/x86/kernel/cpu/common.c       | 12 +++++++++-
 arch/x86/kernel/process.c          |  7 ------
 arch/x86/mm/pti.c                  |  7 +++---
 9 files changed, 40 insertions(+), 62 deletions(-)

-- 
2.19.1.6.gb485710b