Commit Graph

30 Commits

Author SHA1 Message Date
Andy Lutomirski
a798f09111 x86/entry/32: Change INT80 to be an interrupt gate
We want all of the syscall entries to run with interrupts off so that
we can efficiently run context tracking before enabling interrupts.

This will regress int $0x80 performance on 32-bit kernels by a
couple of cycles.  This shouldn't matter much -- int $0x80 is not a
fast path.

This effectively reverts:

  657c1eea00 ("x86/entry/32: Fix entry_INT80_32() to expect interrupts to be on")

... and fixes the same issue differently.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/59b4f90c9ebfccd8c937305dbbbca680bc74b905.1457558566.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-03-10 10:53:26 +01:00
Andy Lutomirski
fda57b2267 x86/entry: Improve system call entry comments
Ingo suggested that the comments should explain when the various
entries are used.  This adds these explanations and improves other
parts of the comments.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/9524ecef7a295347294300045d08354d6a57c6e7.1457578375.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-03-10 09:48:15 +01:00
Andy Lutomirski
7536656f08 x86/entry/32: Simplify and fix up the SYSENTER stack #DB/NMI fixup
Right after SYSENTER, we can get a #DB or NMI.  On x86_32, there's no IST,
so the exception handler is invoked on the temporary SYSENTER stack.

Because the SYSENTER stack is very small, we have a fixup to switch
off the stack quickly when this happens.  The old fixup had several issues:

 1. It checked the interrupt frame's CS and EIP.  This wasn't
    obviously correct on Xen or if vm86 mode was in use [1].

 2. In the NMI handler, it did some frightening digging into the
    stack frame.  I'm not convinced this digging was correct.

 3. The fixup didn't switch stacks and then switch back.  Instead, it
    synthesized a brand new stack frame that would redirect the IRET
    back to the SYSENTER code.  That frame was highly questionable.
    For one thing, if NMI nested inside #DB, we would effectively
    abort the #DB prologue, which was probably safe but was
    frightening.  For another, the code used PUSHFL to write the
    FLAGS portion of the frame, which was simply bogus -- by the time
    PUSHFL was called, at least TF, NT, VM, and all of the arithmetic
    flags were clobbered.

Simplify this considerably.  Instead of looking at the saved frame
to see where we came from, check the hardware ESP register against
the SYSENTER stack directly.  Malicious user code cannot spoof the
kernel ESP register, and by moving the check after SAVE_ALL, we can
use normal PER_CPU accesses to find all the relevant addresses.

With this patch applied, the improved syscall_nt_32 test finally
passes on 32-bit kernels.

[1] It isn't obviously correct, but it is nonetheless safe from vm86
    shenanigans as far as I can tell.  A user can't point EIP at
    entry_SYSENTER_32 while in vm86 mode because entry_SYSENTER_32,
    like all kernel addresses, is greater than 0xffff and would thus
    violate the CS segment limit.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/b2cdbc037031c07ecf2c40a96069318aec0e7971.1457578375.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-03-10 09:48:14 +01:00
Andy Lutomirski
f2b375756c x86/entry: Vastly simplify SYSENTER TF (single-step) handling
Due to a blatant design error, SYSENTER doesn't clear TF (single-step).

As a result, if a user does SYSENTER with TF set, we will single-step
through the kernel until something clears TF.  There is absolutely
nothing we can do to prevent this short of turning off SYSENTER [1].

Simplify the handling considerably with two changes:

  1. We already sanitize EFLAGS in SYSENTER to clear NT and AC.  We can
     add TF to that list of flags to sanitize with no overhead whatsoever.

  2. Teach do_debug() to ignore single-step traps in the SYSENTER prologue.

That's all we need to do.

Don't get too excited -- our handling is still buggy on 32-bit
kernels.  There's nothing wrong with the SYSENTER code itself, but
the #DB prologue has a clever fixup for traps on the very first
instruction of entry_SYSENTER_32, and the fixup doesn't work quite
correctly.  The next two patches will fix that.

[1] We could probably prevent it by forcing BTF on at all times and
    making sure we clear TF before any branches in the SYSENTER
    code.  Needless to say, this is a bad idea.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/a30d2ea06fe4b621fe6a9ef911b02c0f38feb6f2.1457578375.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-03-10 09:48:13 +01:00
Andy Lutomirski
c2c9b52fab x86/entry/32: Restore FLAGS on SYSEXIT
We weren't restoring FLAGS at all on SYSEXIT.  Apparently no one cared.

With this patch applied, native kernels should always honor
task_pt_regs()->flags, which opens the door for some sys_iopl()
cleanups.  I'll do those as a separate series, though, since getting
it right will involve tweaking some paravirt ops.

( The short version is that, before this patch, sys_iopl(), invoked via
  SYSENTER, wasn't guaranteed to ever transfer the updated
  regs->flags, so sys_iopl() had to change the hardware flags register
  as well. )

Reported-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/3f98b207472dc9784838eb5ca2b89dcc845ce269.1457578375.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-03-10 09:48:12 +01:00
Andy Lutomirski
67f590e8d4 x86/entry/32: Filter NT and speed up AC filtering in SYSENTER
This makes the 32-bit code work just like the 64-bit code.  It should
speed up syscalls on 32-bit kernels on Skylake by something like 20
cycles (by analogy to the 64-bit compat case).

It also cleans up NT just like we do for the 64-bit case.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/07daef3d44bd1ed62a2c866e143e8df64edb40ee.1457578375.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-03-10 09:48:12 +01:00
Andy Lutomirski
58a5aac533 x86/entry/32: Introduce and use X86_BUG_ESPFIX instead of paravirt_enabled
x86_64 has very clean espfix handling on paravirt: espfix64 is set
up in native_iret, so paravirt systems that override iret bypass
espfix64 automatically.  This is robust and straightforward.

x86_32 is messier.  espfix is set up before the IRET paravirt patch
point, so it can't be directly conditionalized on whether we use
native_iret.  We also can't easily move it into native_iret without
regressing performance due to a bizarre consideration.  Specifically,
on 64-bit kernels, the logic is:

  if (regs->ss & 0x4)
          setup_espfix;

On 32-bit kernels, the logic is:

  if ((regs->ss & 0x4) && (regs->cs & 0x3) == 3 &&
      (regs->flags & X86_EFLAGS_VM) == 0)
          setup_espfix;

The performance of setup_espfix itself is essentially irrelevant, but
the comparison happens on every IRET so its performance matters.  On
x86_64, there's no need for any registers except flags to implement
the comparison, so we fold the whole thing into native_iret.  On
x86_32, we don't do that because we need a free register to
implement the comparison efficiently.  We therefore do espfix setup
before restoring registers on x86_32.

This patch gets rid of the explicit paravirt_enabled check by
introducing X86_BUG_ESPFIX on 32-bit systems and using an ALTERNATIVE
to skip espfix on paravirt systems where iret != native_iret.  This is
also messy, but it's at least in line with other things we do.

This improves espfix performance by removing a branch, but no one
cares.  More importantly, it removes a paravirt_enabled user, which is
good because paravirt_enabled is ill-defined and is going away.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: boris.ostrovsky@oracle.com
Cc: david.vrabel@citrix.com
Cc: konrad.wilk@oracle.com
Cc: lguest@lists.ozlabs.org
Cc: xen-devel@lists.xensource.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-03-08 14:16:44 +01:00
Ingo Molnar
ec87e1cf7d Linux 4.5-rc7
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Merge tag 'v4.5-rc7' into x86/asm, to pick up SMAP fix

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-03-07 09:27:30 +01:00
Andy Lutomirski
04d1d281dc x86/entry/32: Add an ASM_CLAC to entry_SYSENTER_32
Both before and after 5f310f739b ("x86/entry/32: Re-implement
SYSENTER using the new C path"), we relied on a uaccess very early
in the SYSENTER path to clear AC.  After that change, though, we can
potentially make it all the way into C code with AC set, which
enlarges the attack surface for SMAP bypass by doing SYSENTER with
AC set.

Strengthen the SMAP protection by addding the missing ASM_CLAC right
at the beginning.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/3e36be110724896e32a4a1fe73bacb349d3cba94.1456262295.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-02-24 08:43:04 +01:00
Borislav Petkov
cd4d09ec6f x86/cpufeature: Carve out X86_FEATURE_*
Move them to a separate header and have the following
dependency:

  x86/cpufeatures.h <- x86/processor.h <- x86/cpufeature.h

This makes it easier to use the header in asm code and not
include the whole cpufeature.h and add guards for asm.

Suggested-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1453842730-28463-5-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-01-30 11:22:17 +01:00
Linus Torvalds
88cbfd0711 Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 asm updates from Ingo Molnar:
 "The main changes in this cycle were:

   - vDSO and asm entry improvements (Andy Lutomirski)

   - Xen paravirt entry enhancements (Boris Ostrovsky)

   - asm entry labels enhancement (Borislav Petkov)

   - and other misc changes (Thomas Gleixner, me)"

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/vsdo: Fix build on PARAVIRT_CLOCK=y, KVM_GUEST=n
  Revert "x86/kvm: On KVM re-enable (e.g. after suspend), update clocks"
  x86/entry/64_compat: Make labels local
  x86/platform/uv: Include clocksource.h for clocksource_touch_watchdog()
  x86/vdso: Enable vdso pvclock access on all vdso variants
  x86/vdso: Remove pvclock fixmap machinery
  x86/vdso: Get pvclock data from the vvar VMA instead of the fixmap
  x86, vdso, pvclock: Simplify and speed up the vdso pvclock reader
  x86/kvm: On KVM re-enable (e.g. after suspend), update clocks
  x86/entry/64: Bypass enter_from_user_mode on non-context-tracking boots
  x86/asm: Add asm macros for static keys/jump labels
  x86/asm: Error out if asm/jump_label.h is included inappropriately
  context_tracking: Switch to new static_branch API
  x86/entry, x86/paravirt: Remove the unused usergs_sysret32 PV op
  x86/paravirt: Remove the unused irq_enable_sysexit pv op
  x86/xen: Avoid fast syscall path for Xen PV guests
2016-01-11 15:58:16 -08:00
Andy Lutomirski
30bfa7b348 x86/entry: Restore traditional SYSENTER calling convention
It turns out that some Android versions hardcode the SYSENTER
calling convention.  This is buggy and will cause problems no
matter what the kernel does.  Nonetheless, we should try to
support it.

Credit goes to Linus for pointing out a clean way to handle
the SYSENTER/SYSCALL clobber differences while preserving
straightforward DWARF annotations.

I believe that the original offending Android commit was:

https://android.googlesource.com/platform%2Fbionic/+/7dc3684d7a2587e43e6d2a8e0e3f39bf759bd535

Reported-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-and-tested-by: Borislav Petkov <bp@alien8.de>
Cc: <mark.gross@intel.com>
Cc: Su Tao <tao.su@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: <frank.wang@intel.com>
Cc: <borun.fu@intel.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Mingwei Shi <mingwei.shi@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2015-12-21 16:05:01 +01:00
Andy Lutomirski
6a613ac6bc x86/entry: Fix some comments
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-and-tested-by: Borislav Petkov <bp@alien8.de>
Cc: <mark.gross@intel.com>
Cc: Su Tao <tao.su@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: <qiuxu.zhuo@intel.com>
Cc: <frank.wang@intel.com>
Cc: <borun.fu@intel.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Mingwei Shi <mingwei.shi@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2015-12-21 16:05:01 +01:00
Boris Ostrovsky
91e2eea98f x86/xen: Avoid fast syscall path for Xen PV guests
After 32-bit syscall rewrite, and specifically after commit:

  5f310f739b ("x86/entry/32: Re-implement SYSENTER using the new C path")

... the stack frame that is passed to xen_sysexit is no longer a
"standard" one (i.e. it's not pt_regs).

Since we end up calling xen_iret from xen_sysexit we don't need
to fix up the stack and instead follow entry_SYSENTER_32's IRET
path directly to xen_iret.

We can do the same thing for compat mode even though stack does
not need to be fixed. This will allow us to drop usergs_sysret32
paravirt op (in the subsequent patch)

Suggested-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: david.vrabel@citrix.com
Cc: konrad.wilk@oracle.com
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1447970147-1733-2-git-send-email-boris.ostrovsky@oracle.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2015-12-19 09:55:52 +01:00
Boris Ostrovsky
88c15ec90f x86/paravirt: Remove the unused irq_enable_sysexit pv op
As result of commit "x86/xen: Avoid fast syscall path for Xen PV
guests", the irq_enable_sysexit pv op is not called by Xen PV guests
anymore and since they were the only ones who used it we can
safely remove it.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: david.vrabel@citrix.com
Cc: konrad.wilk@oracle.com
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1447970147-1733-3-git-send-email-boris.ostrovsky@oracle.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-11-23 10:48:16 +01:00
Boris Ostrovsky
5fdf5d37f4 x86/xen: Avoid fast syscall path for Xen PV guests
After 32-bit syscall rewrite, and specifically after commit:

  5f310f739b ("x86/entry/32: Re-implement SYSENTER using the new C path")

... the stack frame that is passed to xen_sysexit is no longer a
"standard" one (i.e. it's not pt_regs).

Since we end up calling xen_iret from xen_sysexit we don't need
to fix up the stack and instead follow entry_SYSENTER_32's IRET
path directly to xen_iret.

We can do the same thing for compat mode even though stack does
not need to be fixed. This will allow us to drop usergs_sysret32
paravirt op (in the subsequent patch)

Suggested-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: david.vrabel@citrix.com
Cc: konrad.wilk@oracle.com
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1447970147-1733-2-git-send-email-boris.ostrovsky@oracle.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-11-23 10:48:16 +01:00
Andy Lutomirski
3bd29515d1 x86/entry/32: Fix FS and GS restore in opportunistic SYSEXIT
We either need to restore them before popping and thus changing
ESP, or we need to adjust the offsets.  The former is simpler.

Reported-and-tested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 5f310f739b x86/entry/32: ("Re-implement SYSENTER using the new C path")
Link: http://lkml.kernel.org/r/461e5c7d8fa3821529893a4893ac9c4bc37f9e17.1445035014.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-18 12:11:16 +02:00
Andy Lutomirski
657c1eea00 x86/entry/32: Fix entry_INT80_32() to expect interrupts to be on
When I rewrote entry_INT80_32, I thought that int80 was an
interrupt gate.  It's a trap gate.  *facepalm*

Thanks to Brian Gerst for pointing out that it's better to
change the entry code than to change the gate type.

Suggested-by: Brian Gerst <brgerst@gmail.com>
Reported-and-tested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 150ac78d63 ("x86/entry/32: Switch INT80 to the new C syscall path")
Link: http://lkml.kernel.org/r/dc09d9b574a5c1dcca996847875c73f8341ce0ad.1445035014.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-18 12:11:16 +02:00
Andy Lutomirski
5f310f739b x86/entry/32: Re-implement SYSENTER using the new C path
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/5b99659e8be70f3dd10cd8970a5c90293d9ad9a7.1444091585.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-09 09:41:10 +02:00
Andy Lutomirski
150ac78d63 x86/entry/32: Switch INT80 to the new C syscall path
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/a7e8d8df96838eae3208dd0441023f3ce7a81831.1444091585.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-09 09:41:10 +02:00
Andy Lutomirski
39e8701f33 x86/entry/32: Open-code return tracking from fork and kthreads
syscall_exit is going away, and return tracing is just a
function call now, so open-code the two non-syscall 32-bit
users.

While we're at it, update the big register layout comment.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/a6b3c472fda7cda0e368c3ccd553dea7447dfdd2.1444091585.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-09 09:41:10 +02:00
Andy Lutomirski
72f924783b x86/entry, locking/lockdep: Move lockdep_sys_exit() to prepare_exit_to_usermode()
Rather than worrying about exactly where LOCKDEP_SYS_EXIT should
go in the asm code, add it to prepare_exit_from_usermode() and
remove all of the asm calls that are followed by
prepare_exit_to_usermode().

LOCKDEP_SYS_EXIT now appears only in the syscall fast paths.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/1736ebe948b845e68120b86b89091f3ec27f5e8e.1444091584.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-07 11:34:07 +02:00
Andy Lutomirski
5d73fc7099 x86/entry/32: Migrate to C exit path
This removes the hybrid asm-and-C implementation of exit work.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eric Paris <eparis@parisplace.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/2baa438619ea6c027b40ec9fceacca52f09c74d09.1438378274.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-08-05 10:54:35 +02:00
Andy Lutomirski
c5f69fde26 x86/entry/32: Remove 32-bit syscall audit optimizations
The asm audit optimizations are ugly and obfuscate the code too
much. Remove them.

This will regress performance if syscall auditing is enabled on
32-bit kernels and SYSENTER is in use. If this becomes a
problem, interested parties are encouraged to implement the
equivalent of the 64-bit opportunistic SYSRET optimization.

Alternatively, a case could be made that, on 32-bit kernels, a
less messy asm audit optimization could be done. 32-bit kernels
don't have the complicated partial register saving tricks that
64-bit kernels have, so the SYSENTER post-syscall path could
just call the audit hooks directly.  Any reimplementation of
this ought to demonstrate that it only calls the audit hook once
per syscall, though, which does not currently appear to be true.

Someone would have to make the case that doing so would be
better than implementing opportunistic SYSEXIT, though.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eric Paris <eparis@parisplace.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/212be39dd8c90b44c4b7bbc678128d6b88bdb9912.1438378274.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-08-05 10:54:35 +02:00
Brian Gerst
5ed92a8ab7 x86/vm86: Use the normal pt_regs area for vm86
Change to use the normal pt_regs area to enter and exit vm86
mode.  This is done by increasing the padding at the top of the
stack to make room for the extra vm86 segment slots in the IRET
frame.  It then saves the 32-bit regs in the off-stack vm86
data, and copies in the vm86 regs.  Exiting back to 32-bit mode
does the reverse.  This allows removing the hacks to jump
directly into the exit asm code due to having to change the
stack pointer.  Returning normally from the vm86 syscall and the
exception handlers allows things like ptrace and auditing to work properly.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1438148483-11932-5-git-send-email-brgerst@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-07-31 13:31:09 +02:00
Denys Vlasenko
9b47feb708 x86/asm/entry: Clean up entry*.S style, final bits
A few bits were missed.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-06-09 11:48:24 +02:00
Ingo Molnar
a49976d14f x86/asm/entry/32: Clean up entry_32.S
Make the 32-bit syscall entry code a bit more readable:

 - use consistent assembly coding style similar to entry_64.S

 - remove old comments that are not true anymore

 - eliminate whitespace noise

 - use consistent vertical spacing

 - fix various comments

No code changed:

  # arch/x86/entry/entry_32.o:

   text    data     bss     dec     hex filename
   6025       0       0    6025    1789 entry_32.o.before
   6025       0       0    6025    1789 entry_32.o.after

md5:
   f3fa16b2b0dca804f052deb6b30ba6cb  entry_32.o.before.asm
   f3fa16b2b0dca804f052deb6b30ba6cb  entry_32.o.after.asm

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-06-08 09:54:24 +02:00
Ingo Molnar
b2502b418e x86/asm/entry: Untangle 'system_call' into two entry points: entry_SYSCALL_64 and entry_INT80_32
The 'system_call' entry points differ starkly between native 32-bit and 64-bit
kernels: on 32-bit kernels it defines the INT 0x80 entry point, while on
64-bit it's the SYSCALL entry point.

This is pretty confusing when looking at generic code, and it also obscures
the nature of the entry point at the assembly level.

So unangle this by splitting the name into its two uses:

	system_call (32) -> entry_INT80_32
	system_call (64) -> entry_SYSCALL_64

As per the generic naming scheme for x86 system call entry points:

	entry_MNEMONIC_qualifier

where 'qualifier' is one of _32, _64 or _compat.

Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-06-08 09:14:21 +02:00
Ingo Molnar
4c8cd0c50d x86/asm/entry: Untangle 'ia32_sysenter_target' into two entry points: entry_SYSENTER_32 and entry_SYSENTER_compat
So the SYSENTER instruction is pretty quirky and it has different behavior
depending on bitness and CPU maker.

Yet we create a false sense of coherency by naming it 'ia32_sysenter_target'
in both of the cases.

Split the name into its two uses:

	ia32_sysenter_target (32)    -> entry_SYSENTER_32
	ia32_sysenter_target (64)    -> entry_SYSENTER_compat

As per the generic naming scheme for x86 system call entry points:

	entry_MNEMONIC_qualifier

where 'qualifier' is one of _32, _64 or _compat.

Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-06-08 08:47:46 +02:00
Ingo Molnar
905a36a285 x86/asm/entry: Move entry_64.S and entry_32.S to arch/x86/entry/
Create a new directory hierarchy for the low level x86 entry code:

    arch/x86/entry/*

This will host all the low level glue that is currently scattered
all across arch/x86/.

Start with entry_64.S and entry_32.S.

Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-06-03 18:51:28 +02:00