patches/kernel/0092-x86-entry-64-Merge-the-fast-and-slow-SYSRET-paths.patch

   1 From c48697564de6da427f1e97a38192f4d456223942 Mon Sep 17 00:00:00 2001
   2 From: Andy Lutomirski <luto@kernel.org>
   3 Date: Thu, 2 Nov 2017 00:59:04 -0700
   4 Subject: [PATCH 092/233] x86/entry/64: Merge the fast and slow SYSRET paths
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 CVE-2017-5754
  10
  11 They did almost the same thing.  Remove a bunch of pointless
  12 instructions (mostly hidden in macros) and reduce cognitive load by
  13 merging them.
  14
  15 Signed-off-by: Andy Lutomirski <luto@kernel.org>
  16 Cc: Borislav Petkov <bpetkov@suse.de>
  17 Cc: Brian Gerst <brgerst@gmail.com>
  18 Cc: Dave Hansen <dave.hansen@intel.com>
  19 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  20 Cc: Peter Zijlstra <peterz@infradead.org>
  21 Cc: Thomas Gleixner <tglx@linutronix.de>
  22 Link: http://lkml.kernel.org/r/1204e20233fcab9130a1ba80b3b1879b5db3fc1f.1509609304.git.luto@kernel.org
  23 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  24 (cherry picked from commit a512210643da8082cb44181dba8b18e752bd68f0)
  25 Signed-off-by: Andy Whitcroft <apw@canonical.com>
  26 Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
  27 (cherry picked from commit 7c4575d8bb2d01960ba9b9840fa22460e0179eca)
  28 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  29 ---
  30  arch/x86/entry/entry_64.S | 6 +++---
  31  1 file changed, 3 insertions(+), 3 deletions(-)
  32
  33 diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
  34 index 33a416c7df2d..87be1cd1fa88 100644
  35 --- a/arch/x86/entry/entry_64.S
  36 +++ b/arch/x86/entry/entry_64.S
  37 @@ -220,10 +220,9 @@ entry_SYSCALL_64_fastpath:
  38         TRACE_IRQS_ON           /* user mode is traced as IRQs on */
  39         movq    RIP(%rsp), %rcx
  40         movq    EFLAGS(%rsp), %r11
  41 -       RESTORE_C_REGS_EXCEPT_RCX_R11
  42 -       movq    RSP(%rsp), %rsp
  43 +       addq    $6*8, %rsp      /* skip extra regs -- they were preserved */
  44         UNWIND_HINT_EMPTY
  45 -       USERGS_SYSRET64
  46 +       jmp     .Lpop_c_regs_except_rcx_r11_and_sysret
  47
  48  1:
  49         /*
  50 @@ -317,6 +316,7 @@ syscall_return_via_sysret:
  51         /* rcx and r11 are already restored (see code above) */
  52         UNWIND_HINT_EMPTY
  53         POP_EXTRA_REGS
  54 +.Lpop_c_regs_except_rcx_r11_and_sysret:
  55         popq    %rsi    /* skip r11 */
  56         popq    %r10
  57         popq    %r9
  58 --
  59 2.14.2
  60