Remove open-coded exception table entries in arch/x86/kernel/entry_64.S,
and replace them with _ASM_EXTABLE() macros; this will allow us to
change the format and type of the exception table entries.
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
Cc: David Daney <david.daney@cavium.com>
Link: http://lkml.kernel.org/r/CA%2B55aFyijf43qSu3N9nWHEBwaGbb7T2Oq9A=9EyR=Jtyqfq_cQ@mail.gmail.com

Commit eab9e613 ("x86-64: Fix CFI data for interrupt frames")
introduced a DW_CFA_def_cfa_expression in the SAVE_ARGS_IRQ
macro. To later define the CFA using a simple register+offset
rule both register and offset need to be supplied. Just using
CFI_DEF_CFA_REGISTER leaves the offset undefined. So use
CFI_DEF_CFA with reg+off explicitly at the end of
common_interrupt.
Signed-off-by: NMark Wielaard <mjw@redhat.com>
Acked-by: NJan Beulich <jbeulich@suse.com>
Link: http://lkml.kernel.org/r/1330079527-30711-1-git-send-email-mjw@redhat.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

Some of the comments for the nesting NMI algorithm were stale and
had some references to some prototypes that were first tried.

I also updated the comments to be a little easier to understand
the flow of the code. It definitely needs the documentation.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

In one case, use an address register that was computed earlier (and
with a simpler instruction), thus reducing the risk of a stall.

In the second case, eliminate a branch by using a conditional move (as
is already done in call_softirq and xen_do_hypervisor_callback).
Signed-off-by: NJan Beulich <jbeulich@suse.com>
Link: http://lkml.kernel.org/r/4F4788A50200007800074A26@nat28.tlf.novell.comReviewed-by: NAndi Kleen <ak@linux.intel.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

The saving and restoring of %rdx wasn't annotated at all, and the
jumping over sections where state gets partly restored wasn't handled
either.

Further, by folding the pushing of the previous frame in repeat_nmi
into that which so far was immediately preceding restart_nmi (after
moving the restore of %rdx ahead of that, since it doesn't get used
anymore when pushing prior frames), annotations of the replicated
frame creations can be made consistent too.

v2: Fully fold repeat_nmi into the normal code flow (adding a single
    redundant instruction to the "normal" code path), thus retaining
    the special protection of all instructions between repeat_nmi and
    end_repeat_nmi.

Link: http://lkml.kernel.org/r/4F478B630200007800074A31@nat28.tlf.novell.comSigned-off-by: NJan Beulich <jbeulich@suse.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Linus noticed that the cmp used to check if the code segment is
__KERNEL_CS or not did not specify a size. Perhaps it does not matter
as H. Peter Anvin noted that user space can not set the bottom two
bits of the %cs register. But it's best not to let the assembly choose
and change things between different versions of gas, but instead just
pick the size.

Four bytes are used to compare the saved code segment against
__KERNEL_CS. Perhaps this might mess up Xen, but we can fix that when
the time comes.

Also I noticed that there was another non-specified cmp that checks
the special stack variable if it is 1 or 0. This too probably doesn't
matter what cmp is used, but this patch uses cmpl just to make it non
ambiguous.

Link: http://lkml.kernel.org/r/CA+55aFxfAn9MWRgS3O5k2tqN5ys1XrhSFVO5_9ZAoZKDVgNfGA@mail.gmail.comSuggested-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Allow an x32 process to be started.
Originally-by: NH. J. Lu <hjl.tools@gmail.com>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>

x32 uses the 64-bit signal frame format, obviously, but there are some
structures which mixes that with pointers or sizeof(long) types, as
such we have to create a handful of system calls specific to x32.  By
and large these are a mixture of the 64-bit and the compat system
calls.
Originally-by: NH. J. Lu <hjl.tools@gmail.com>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

x32 shares most system calls with x86-64, but unfortunately some
subsystem (the input subsystem is the chief offender) which require
is_compat() when operating with a 32-bit userspace.  The input system
actually has text files in sysfs whose meaning is dependent on
sizeof(long) in userspace!

We could solve this by having two completely disjoint system call
tables; requiring that each system call be duplicated.  This patch
takes a different approach: we add a flag to the system call number;
this flag doesn't affect the system call dispatch but requests compat
treatment from affected subsystems for the duration of the system call.

The change of cmpq to cmpl is safe since it immediately follows the
and.
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

Currently, the NMI handler tests if it is nested by checking the
special variable saved on the stack (set during NMI handling)
and whether the saved stack is the NMI stack as well (to prevent
the race when the variable is set to zero).

But userspace may set their %rsp to any value as long as they do
not derefence it, and it may make it point to the NMI stack,
which will prevent NMIs from triggering while the userspace app
is running. (I tested this, and it is indeed the case)

Add another check to determine nested NMIs by looking at the
saved %cs (code segment register) and making sure that it is the
kernel code segment.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: <stable@kernel.org>
Link: http://lkml.kernel.org/r/1329687817.1561.27.camel@acer.local.homeSigned-off-by: NIngo Molnar <mingo@elte.hu>

Every arch calls:

if (unlikely(current->audit_context))
	audit_syscall_entry()

which requires knowledge about audit (the existance of audit_context) in
the arch code.  Just do it all in static inline in audit.h so that arch's
can remain blissfully ignorant.
Signed-off-by: NEric Paris <eparis@redhat.com>

The audit system previously expected arches calling to audit_syscall_exit to
supply as arguments if the syscall was a success and what the return code was.
Audit also provides a helper AUDITSC_RESULT which was supposed to simplify things
by converting from negative retcodes to an audit internal magic value stating
success or failure.  This helper was wrong and could indicate that a valid
pointer returned to userspace was a failed syscall.  The fix is to fix the
layering foolishness.  We now pass audit_syscall_exit a struct pt_reg and it
in turns calls back into arch code to collect the return value and to
determine if the syscall was a success or failure.  We also define a generic
is_syscall_success() macro which determines success/failure based on if the
value is < -MAX_ERRNO.  This works for arches like x86 which do not use a
separate mechanism to indicate syscall failure.

We make both the is_syscall_success() and regs_return_value() static inlines
instead of macros.  The reason is because the audit function must take a void*
for the regs.  (uml calls theirs struct uml_pt_regs instead of just struct
pt_regs so audit_syscall_exit can't take a struct pt_regs).  Since the audit
function takes a void* we need to use static inlines to cast it back to the
arch correct structure to dereference it.

The other major change is that on some arches, like ia64, MIPS and ppc, we
change regs_return_value() to give us the negative value on syscall failure.
THE only other user of this macro, kretprobe_example.c, won't notice and it
makes the value signed consistently for the audit functions across all archs.

In arch/sh/kernel/ptrace_64.c I see that we were using regs[9] in the old
audit code as the return value.  But the ptrace_64.h code defined the macro
regs_return_value() as regs[3].  I have no idea which one is correct, but this
patch now uses the regs_return_value() function, so it now uses regs[3].

For powerpc we previously used regs->result but now use the
regs_return_value() function which uses regs->gprs[3].  regs->gprs[3] is
always positive so the regs_return_value(), much like ia64 makes it negative
before calling the audit code when appropriate.
Signed-off-by: NEric Paris <eparis@redhat.com>
Acked-by: H. Peter Anvin <hpa@zytor.com> [for x86 portion]
Acked-by: Tony Luck <tony.luck@intel.com> [for ia64]
Acked-by: Richard Weinberger <richard@nod.at> [for uml]
Acked-by: David S. Miller <davem@davemloft.net> [for sparc]
Acked-by: Ralf Baechle <ralf@linux-mips.org> [for mips]
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> [for ppc]

In x86, when an NMI goes off, the CPU goes into an NMI context that
prevents other NMIs to trigger on that CPU. If an NMI is suppose to
trigger, it has to wait till the previous NMI leaves NMI context.
At that time, the next NMI can trigger (note, only one more NMI will
trigger, as only one can be latched at a time).

The way x86 gets out of NMI context is by calling iret. The problem
with this is that this causes problems if the NMI handle either
triggers an exception, or a breakpoint. Both the exception and the
breakpoint handlers will finish with an iret. If this happens while
in NMI context, the CPU will leave NMI context and a new NMI may come
in. As NMI handlers are not made to be re-entrant, this can cause
havoc with the system, not to mention, the nested NMI will write
all over the previous NMI's stack.

Linus Torvalds proposed the following workaround to this problem:

https://lkml.org/lkml/2010/7/14/264

"In fact, I wonder if we couldn't just do a software NMI disable
instead? Hav ea per-cpu variable (in the _core_ percpu areas that get
allocated statically) that points to the NMI stack frame, and just
make the NMI code itself do something like

 NMI entry:
 - load percpu NMI stack frame pointer
 - if non-zero we know we're nested, and should ignore this NMI:
    - we're returning to kernel mode, so return immediately by using
"popf/ret", which also keeps NMI's disabled in the hardware until the
"real" NMI iret happens.
    - before the popf/iret, use the NMI stack pointer to make the NMI
return stack be invalid and cause a fault
  - set the NMI stack pointer to the current stack pointer

 NMI exit (not the above "immediate exit because we nested"):
   clear the percpu NMI stack pointer
   Just do the iret.

Now, the thing is, now the "iret" is atomic. If we had a nested NMI,
we'll take a fault, and that re-does our "delayed" NMI - and NMI's
will stay masked.

And if we didn't have a nested NMI, that iret will now unmask NMI's,
and everything is happy."

I first tried to follow this advice but as I started implementing this
code, a few gotchas showed up.

One, is accessing per-cpu variables in the NMI handler.

The problem is that per-cpu variables use the %gs register to get the
variable for the given CPU. But as the NMI may happen in userspace,
we must first perform a SWAPGS to get to it. The NMI handler already
does this later in the code, but its too late as we have saved off
all the registers and we don't want to do that for a disabled NMI.

Peter Zijlstra suggested to keep all variables on the stack. This
simplifies things greatly and it has the added benefit of cache locality.

Two, faulting on the iret.

I really wanted to make this work, but it was becoming very hacky, and
I never got it to be stable. The iret already had a fault handler for
userspace faulting with bad segment registers, and getting NMI to trigger
a fault and detect it was very tricky. But for strange reasons, the system
would usually take a double fault and crash. I never figured out why
and decided to go with a simple "jmp" approach. The new approach I took
also simplified things.

Finally, the last problem with Linus's approach was to have the nested
NMI handler do a ret instead of an iret to give the first NMI NMI-context
again.

The problem is that ret is much more limited than an iret. I couldn't figure
out how to get the stack back where it belonged. I could have copied the
current stack, pushed the return onto it, but my fear here is that there
may be some place that writes data below the stack pointer. I know that
is not something code should depend on, but I don't want to chance it.
I may add this feature later, but for now, an NMI handler that loses NMI
context will not get it back.

Here's what is done:

When an NMI comes in, the HW pushes the interrupt stack frame onto the
per cpu NMI stack that is selected by the IST.

A special location on the NMI stack holds a variable that is set when
the first NMI handler runs. If this variable is set then we know that
this is a nested NMI and we process the nested NMI code.

There is still a race when this variable is cleared and an NMI comes
in just before the first NMI does the return. For this case, if the
variable is cleared, we also check if the interrupted stack is the
NMI stack. If it is, then we process the nested NMI code.

Why the two tests and not just test the interrupted stack?

If the first NMI hits a breakpoint and loses NMI context, and then it
hits another breakpoint and while processing that breakpoint we get a
nested NMI. When processing a breakpoint, the stack changes to the
breakpoint stack. If another NMI comes in here we can't rely on the
interrupted stack to be the NMI stack.

If the variable is not set and the interrupted task's stack is not the
NMI stack, then we know this is the first NMI and we can process things
normally. But in order to do so, we need to do a few things first.

1) Set the stack variable that tells us that we are in an NMI handler

2) Make two copies of the interrupt stack frame.
   One copy is used to return on iret
   The other is used to restore the first one if we have a nested NMI.

This is what the stack will look like:

	  +-------------------------+
	  | original SS             |
	  | original Return RSP     |
	  | original RFLAGS         |
	  | original CS             |
	  | original RIP            |
	  +-------------------------+
	  | temp storage for rdx    |
	  +-------------------------+
	  | NMI executing variable  |
	  +-------------------------+
	  | Saved SS                |
	  | Saved Return RSP        |
	  | Saved RFLAGS            |
	  | Saved CS                |
	  | Saved RIP               |
	  +-------------------------+
	  | copied SS               |
	  | copied Return RSP       |
	  | copied RFLAGS           |
	  | copied CS               |
	  | copied RIP              |
	  +-------------------------+
	  | pt_regs                 |
	  +-------------------------+

The original stack frame contains what the HW put in when we entered
the NMI.

We store %rdx as a temp variable to use. Both the original HW stack
frame and this %rdx storage will be clobbered by nested NMIs so we
can not rely on them later in the first NMI handler.

The next item is the special stack variable that is set when we execute
the rest of the NMI handler.

Then we have two copies of the interrupt stack. The second copy is
modified by any nested NMIs to let the first NMI know that we triggered
a second NMI (latched) and that we should repeat the NMI handler.

If the first NMI hits an exception or breakpoint that takes it out of
NMI context, if a second NMI comes in before the first one finishes,
it will update the copied interrupt stack to point to a fix up location
to trigger another NMI.

When the first NMI calls iret, it will instead jump to the fix up
location. This fix up location will copy the saved interrupt stack back
to the copy and execute the nmi handler again.

Note, the nested NMI knows enough to check if it preempted a previous
NMI handler while it is in the fixup location. If it has, it will not
modify the copied interrupt stack and will just leave as if nothing
happened. As the NMI handle is about to execute again, there's no reason
to latch now.

To test all this, I forced the NMI handler to call iret and take itself
out of NMI context. I also added assemble code to write to the serial to
make sure that it hits the nested path as well as the fix up path.
Everything seems to be working fine.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul Turner <pjt@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Linus cleaned up the NMI handler but it still needs some comments to
explain why it uses save_paranoid but not paranoid_exit. Just to keep
others from adding that in the future, document why it's not used.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The NMI handler uses the paranoid_exit routine that checks the
NEED_RESCHED flag, and if it is set and the return is for userspace,
then interrupts are enabled, the stack is swapped to the thread's stack,
and schedule is called. The problem with this is that we are still in an
NMI context until an iret is executed. This means that any new NMIs are
now starved until an interrupt or exception occurs and does the iret.

As NMIs can not be masked and can interrupt any location, they are
treated as a special case. NEED_RESCHED should not be set in an NMI
handler. The interruption by the NMI should not disturb the work flow
for scheduling. Any IPI sent to a processor after sending the
NEED_RESCHED would have to wait for the NMI anyway, and after the IPI
finishes the schedule would be called as required.

There is no reason to do anything special leaving an NMI. Remove the
call to paranoid_exit and do a simple return. This not only fixes the
bug of starved NMIs, but it also cleans up the code.

Link: http://lkml.kernel.org/r/CA+55aFzgM55hXTs4griX5e9=v_O+=ue+7Rj0PTD=M7hFYpyULQ@mail.gmail.comAcked-by: NAndi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "H. Peter Anvin" <hpa@linux.intel.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul Turner <pjt@google.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The x86_64 kernel pushes the fake kernel stack in
arch/x86/kernel/entry_64.S:FAKE_STACK_FRAME, and
rflags register in it does not conform to the specification.

Although Intel's manual[1] says bit 1 of it shall be set to 1,
this bit is cleared to 0 on pushing the fake stack.

[1] Intel(R) 64 and IA-32 Architectures Software Developer's Manual
    Vol.1 3-21 Figure 3-8. EFLAGS Register

If it is not on purpose, it is better to be fixed, because
it can lead some tools misunderstanding the stack frame. For example,
"crash" utility[2] actually detects it and warns you like
below:

       RIP: ffffffff8005dfa2  RSP: ffff8104ce0c7f58  RFLAGS: 00000200
       [...]

       bt: WARNING: possibly bogus exception frame
Signed-off-by: NSeiichi Ikarashi <s.ikarashi@jp.fujitsu.com>
Tested-by: NMasayoshi MIZUMA <m.mizuma@jp.fujitsu.com>
Cc: Jan Beulich <JBeulich@suse.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

system_call_after_swapgs doesn't really benefit from forcing
alignment from it - quite the opposite, native code needlessly
so far got a big NOP instruction inserted in front of it. Xen
being the only user of the separate entry point can well live
with the branch going to three bytes into a cache line.

The compatibility mode ptregs entry points for one can make use
of the GLOBAL() macro, and should be suitably aligned. Their
shared continuation point (ia32_ptregs_common) otoh doesn't need
to be global at all, but should continue to be properly aligned.
Signed-off-by: NJan Beulich <jbeulich@suse.com>
Reviewed-by: NAndi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/4ED4CEEA020000780006407D@nat28.tlf.novell.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

GET_THREAD_INFO() involves a memory read immediately followed by
an "sub" on the value read, in turn (in several cases)
immediately followed by a use of the calculated value as the
base address of a memory access. This combination of
instructions has a non-negligible potential for stalls.

In the system call entry point code, however, the (fixed) offset
of the stack pointer from the end of the stack is generally
known, and hence we can instead avoid the memory load and
subtract, and instead do the memory reference using %rsp as the
base register. To do so in a legible fashion, introduce a
THREAD_INFO() macro which, provided a register (generally %rsp)
and the known offset from the end of the stack, produces a
suitable memory access operand.

The patch attempts to only touch the fast paths (no auditing and
alike), but manages to do so only in the 64-bit entry point
case; the compatibility mode entry points have so many
interdependencies between their various branch targets that it
was necessary to also adjust the slow paths to eliminate the
risk of having missed some register dependency during code
analysis.
Signed-off-by: NJan Beulich <jbeulich@suse.com>
Reviewed-by: NAndi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/4ED4CD690200007800064075@nat28.tlf.novell.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

Previously these up to 32 entry points, consisting of all the
same code except for their very first instruction, consumed 0x70
bytes per instance. Just like for device interrupt entry points,
fold them together so that they all use a single instance of the
code after having pushed their vector indicator (resulting in
0x10 bytes per instance, to retain 16-byte alignment of the
individual entry points).
Signed-off-by: NJan Beulich <jbeulich@suse.com>
Reviewed-by: NAndi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/4ED4CA230200007800064065@nat28.tlf.novell.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

Testing for a return to ring 0 was necessary here solely because
of the branch out of ret_from_fork. That branch, however, can be
directed to retint_restore_args, and thus the test-and-branch
can be eliminated here.
Signed-off-by: NJan Beulich <jbeulich@suse.com>
Reviewed-by: NAndi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/4ED4C7EE0200007800064028@nat28.tlf.novell.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

The patch titled "x86: Don't use frame pointer to save old stack
on irq entry" did not properly adjust CFI directives, so this
patch is a follow-up to that one.

With the old stack pointer no longer stored in a callee-saved
register (plus some offset), we now have to use a CFA expression
to describe the memory location where it is being found. This
requires the use of .cfi_escape (allowing arbitrary byte streams
to be emitted into .eh_frame), as there is no
.cfi_def_cfa_expression (which also cannot reasonably be
expected, as it would require a full expression parser).
Signed-off-by: NJan Beulich <jbeulich@suse.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/4E8360200200007800058467@nat28.tlf.novell.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

There are three choices:

vsyscall=native: Vsyscalls are native code that issues the
corresponding syscalls.

vsyscall=emulate (default): Vsyscalls are emulated by instruction
fault traps, tested in the bad_area path.  The actual contents of
the vsyscall page is the same as the vsyscall=native case except
that it's marked NX.  This way programs that make assumptions about
what the code in the page does will not be confused when they read
that code.

vsyscall=none: Trying to execute a vsyscall will segfault.
Signed-off-by: NAndy Lutomirski <luto@mit.edu>
Link: http://lkml.kernel.org/r/8449fb3abf89851fd6b2260972666a6f82542284.1312988155.git.luto@mit.eduSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

rbp is used in SAVE_ARGS_IRQ to save the old stack pointer
in order to restore it later in ret_from_intr.

It is convenient because we save its value in the irq regs
and it's easily restored using the leave instruction.

However this is a kind of abuse of the frame pointer which
role is to help unwinding the kernel by chaining frames
together, each node following the return address to the
previous frame.

But although we are breaking the frame by changing the stack
pointer, there is no preceding return address before the new
frame. Hence using the frame pointer to link the two stacks
breaks the stack unwinders that find a random value instead of
a return address here.

There is no workaround that can work in every case. We are using
the fixup_bp_irq_link() function to dereference that abused frame
pointer in the case of non nesting interrupt (which means stack
changed).
But that doesn't fix the case of interrupts that don't change the
stack (but we still have the unconditional frame link), which is
the case of hardirq interrupting softirq. We have no way to detect
this transition so the frame irq link is considered as a real frame
pointer and the return address is dereferenced but it is still a
spurious one.

There are two possible results of this: either the spurious return
address, a random stack value, luckily belongs to the kernel text
and then the unwinding can continue and we just have a weird entry
in the stack trace. Or it doesn't belong to the kernel text and
unwinding stops there.

This is the reason why stacktraces (including perf callchains) on
irqs that interrupted softirqs don't work very well.

To solve this, we don't save the old stack pointer on rbp anymore
but we save it to a scratch register that we push on the new
stack and that we pop back later on irq return.

This preserves the whole frame chain without spurious return addresses
in the middle and drops the need for the horrid fixup_bp_irq_link()
workaround.

And finally irqs that interrupt softirq are sanely unwinded.

Before:

    99.81%         perf  [kernel.kallsyms]  [k] perf_pending_event
                   |
                   --- perf_pending_event
                       irq_work_run
                       smp_irq_work_interrupt
                       irq_work_interrupt
                      |
                      |--41.60%-- __read
                      |          |
                      |          |--99.90%-- create_worker
                      |          |          bench_sched_messaging
                      |          |          cmd_bench
                      |          |          run_builtin
                      |          |          main
                      |          |          __libc_start_main
                      |           --0.10%-- [...]

After:

     1.64%  swapper  [kernel.kallsyms]  [k] perf_pending_event
            |
            --- perf_pending_event
                irq_work_run
                smp_irq_work_interrupt
                irq_work_interrupt
               |
               |--95.00%-- arch_irq_work_raise
               |          irq_work_queue
               |          __perf_event_overflow
               |          perf_swevent_overflow
               |          perf_swevent_event
               |          perf_tp_event
               |          perf_trace_softirq
               |          __do_softirq
               |          call_softirq
               |          do_softirq
               |          irq_exit
               |          |
               |          |--73.68%-- smp_apic_timer_interrupt
               |          |          apic_timer_interrupt
               |          |          |
               |          |          |--96.43%-- amd_e400_idle
               |          |          |          cpu_idle
               |          |          |          start_secondary
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jan Beulich <JBeulich@novell.com>

The unwinder backlink in interrupt entry is very useless.
It's actually not part of the stack frame chain and thus is
never used.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jan Beulich <JBeulich@novell.com>

Just for clarity in the code. Have a first block that handles
the frame pointer and a separate one that handles pt_regs
pointer and its use.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jan Beulich <JBeulich@novell.com>

The save_regs function that saves the regs on low level
irq entry is complicated because of the fact it changes
its stack in the middle and also because it manipulates
data allocated in the caller frame and accesses there
are directly calculated from callee rsp value with the
return address in the middle of the way.

This complicates the static stack offsets calculation and
require more dynamic ones. It also needs a save/restore
of the function's return address.

To simplify and optimize this, turn save_regs() into a
macro.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jan Beulich <JBeulich@novell.com>

The MCE handler uses a special vector for self IPI to invoke
post-emergency processing in an interrupt context, e.g. call an
NMI-unsafe function, wakeup loggers, schedule time-consuming work for
recovery, etc.

This mechanism is now generalized by the following commit:

 > e360adbe
 > Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
 > Date:   Thu Oct 14 14:01:34 2010 +0800
 >
 >  irq_work: Add generic hardirq context callbacks
 >
 >  Provide a mechanism that allows running code in IRQ context. It is
 >  most useful for NMI code that needs to interact with the rest of the
 >  system -- like wakeup a task to drain buffers.
 :

So change to use provided generic mechanism.
Signed-off-by: NHidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Acked-by: NTony Luck <tony.luck@intel.com>
Link: http://lkml.kernel.org/r/4DEED6B2.6080005@jp.fujitsu.comSigned-off-by: NBorislav Petkov <borislav.petkov@amd.com>

There's a fair amount of code in the vsyscall page.  It contains
a syscall instruction (in the gettimeofday fallback) and who
knows what will happen if an exploit jumps into the middle of
some other code.

Reduce the risk by replacing the vsyscalls with short magic
incantations that cause the kernel to emulate the real
vsyscalls. These incantations are useless if entered in the
middle.

This causes vsyscalls to be a little more expensive than real
syscalls.  Fortunately sensible programs don't use them.
The only exception is time() which is still called by glibc
through the vsyscall - but calling time() millions of times
per second is not sensible. glibc has this fixed in the
development tree.

This patch is not perfect: the vread_tsc and vread_hpet
functions are still at a fixed address.  Fixing that might
involve making alternative patching work in the vDSO.
Signed-off-by: NAndy Lutomirski <luto@mit.edu>
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Jesper Juhl <jj@chaosbits.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Jan Beulich <JBeulich@novell.com>
Cc: richard -rw- weinberger <richard.weinberger@gmail.com>
Cc: Mikael Pettersson <mikpe@it.uu.se>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Louis Rilling <Louis.Rilling@kerlabs.com>
Cc: Valdis.Kletnieks@vt.edu
Cc: pageexec@freemail.hu
Link: http://lkml.kernel.org/r/e64e1b3c64858820d12c48fa739efbd1485e79d5.1307292171.git.luto@mit.edu
[ Removed the CONFIG option - it's simpler to just do it unconditionally. Tidied up the code as well. ]
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Signed-off-by: NAndy Lutomirski <luto@mit.edu>
Cc: Jesper Juhl <jj@chaosbits.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Jan Beulich <JBeulich@novell.com>
Cc: richard -rw- weinberger <richard.weinberger@gmail.com>
Cc: Mikael Pettersson <mikpe@it.uu.se>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Louis Rilling <Louis.Rilling@kerlabs.com>
Cc: Valdis.Kletnieks@vt.edu
Cc: pageexec@freemail.hu
Link: http://lkml.kernel.org/r/fc134867cc550977cc996866129e11a16ba0f9ea.1307292171.git.luto@mit.eduSigned-off-by: NIngo Molnar <mingo@elte.hu>

... thus getting rid of the "else" part of the conditional statement in
the macro.

No functionality change.
Signed-off-by: NBorislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/1306873314-32523-4-git-send-email-bp@alien8.deSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

This saves us the else part of the conditional statement in the macro.

No functionality change.
Signed-off-by: NBorislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/1306873314-32523-3-git-send-email-bp@alien8.deSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

They were generated by 'codespell' and then manually reviewed.
Signed-off-by: NLucas De Marchi <lucas.demarchi@profusion.mobi>
Cc: trivial@kernel.org
LKML-Reference: <1300389856-1099-3-git-send-email-lucas.demarchi@profusion.mobi>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The latest binutils (2.21.0.20110302/Ubuntu) breaks the build
yet another time, under CONFIG_XEN=y due to a .size directive that
refers to a slightly differently named (hence, to the now very
strict and unforgiving assembler, non-existent) symbol.

[ mingo:

   This unnecessary build breakage caused by new binutils
   version 2.21 gets escallated back several kernel releases spanning
   several years of Linux history, affecting over 130,000 upstream
   kernel commits (!), on CONFIG_XEN=y 64-bit kernels (i.e. essentially
   affecting all major Linux distro kernel configs).

   Git annotate tells us that this slight debug symbol code mismatch
   bug has been introduced in 2008 in commit 3d75e1b8:

     3d75e1b8        (Jeremy Fitzhardinge    2008-07-08 15:06:49 -0700 1231) ENTRY(xen_do_hypervisor_callback)   # do_hypervisor_callback(struct *pt_regs)

   The 'bug' is just a slight assymetry in ENTRY()/END()
   debug-symbols sequences, with lots of assembly code between the
   ENTRY() and the END():

     ENTRY(xen_do_hypervisor_callback)   # do_hypervisor_callback(struct *pt_regs)
       ...
     END(do_hypervisor_callback)

   Human reviewers almost never catch such small mismatches, and binutils
   never even warned about it either.

   This new binutils version thus breaks the Xen build on all upstream kernels
   since v2.6.27, out of the blue.

   This makes a straightforward Git bisection of all 64-bit Xen-enabled kernels
   impossible on such binutils, for a bisection window of over hundred
   thousand historic commits. (!)

   This is a major fail on the side of binutils and binutils needs to turn
   this show-stopper build failure into a warning ASAP. ]
Signed-off-by: NAlexander van Heukelum <heukelum@fastmail.fm>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Jan Beulich <jbeulich@novell.com>
Cc: H.J. Lu <hjl.tools@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <kees.cook@canonical.com>
LKML-Reference: <1299877178-26063-1-git-send-email-heukelum@fastmail.fm>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Put x86 entry code into a separate link section: .entry.text.

Separating the entry text section seems to have performance
benefits - caused by more efficient instruction cache usage.

Running hackbench with perf stat --repeat showed that the change
compresses the icache footprint. The icache load miss rate went
down by about 15%:

 before patch:
         19417627  L1-icache-load-misses      ( +-   0.147% )

 after patch:
         16490788  L1-icache-load-misses      ( +-   0.180% )

The motivation of the patch was to fix a particular kprobes
bug that relates to the entry text section, the performance
advantage was discovered accidentally.

Whole perf output follows:

 - results for current tip tree:

  Performance counter stats for './hackbench/hackbench 10' (500 runs):

         19417627  L1-icache-load-misses      ( +-   0.147% )
       2676914223  instructions             #      0.497 IPC     ( +- 0.079% )
       5389516026  cycles                     ( +-   0.144% )

      0.206267711  seconds time elapsed   ( +-   0.138% )

 - results for current tip tree with the patch applied:

  Performance counter stats for './hackbench/hackbench 10' (500 runs):

         16490788  L1-icache-load-misses      ( +-   0.180% )
       2717734941  instructions             #      0.502 IPC     ( +- 0.079% )
       5414756975  cycles                     ( +-   0.148% )

      0.206747566  seconds time elapsed   ( +-   0.137% )
Signed-off-by: NJiri Olsa <jolsa@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: masami.hiramatsu.pt@hitachi.com
Cc: ananth@in.ibm.com
Cc: davem@davemloft.net
Cc: 2nddept-manager@sdl.hitachi.co.jp
LKML-Reference: <20110307181039.GB15197@jolsa.redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Add up to 32 invalidate_interrupt handlers. How many handlers are
added depends on NUM_INVALIDATE_TLB_VECTORS. So if
NUM_INVALIDATE_TLB_VECTORS is smaller than 32, we reduce code
size.
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
LKML-Reference: <1295232725.1949.708.camel@sli10-conroe>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

When async PF capability is detected hook up special page fault handler
that will handle async page fault events and bypass other page faults to
regular page fault handler. Also add async PF handling to nested SVM
emulation. Async PF always generates exit to L1 where vcpu thread will
be scheduled out until page is available.
Acked-by: NRik van Riel <riel@redhat.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

From the x86_64 low level interrupt handlers, the frame pointer is
saved right after the partial pt_regs frame.

rbp is not supposed to be part of the irq partial saved registers,
but it only requires to extend the pt_regs frame by 8 bytes to
do so, plus a tiny stack offset fixup on irq exit.

This changes a bit the semantics or get_irq_entry() that is supposed
to provide only the value of caller saved registers and the cpu
saved frame. However it's a win for unwinders that can walk through
stack frames on top of get_irq_regs() snapshots.

A noticeable impact is that it makes perf events cpu-clock and
task-clock events based callchains working on x86_64.

Let's then save rbp into the irq pt_regs.

As a result with:

	perf record -e cpu-clock perf bench sched messaging
	perf report --stdio

Before:
    20.94%             perf  [kernel.kallsyms]        [k] lock_acquire
                       |
                       --- lock_acquire
                          |
                          |--44.01%-- __write_nocancel
                          |
                          |--43.18%-- __read
                          |
                          |--6.08%-- fork
                          |          create_worker
                          |
                          |--0.88%-- _dl_fixup
                          |
                          |--0.65%-- do_lookup_x
                          |
                          |--0.53%-- __GI___libc_read
                           --4.67%-- [...]

After:
    19.23%         perf  [kernel.kallsyms]    [k] __lock_acquire
                   |
                   --- __lock_acquire
                      |
                      |--97.74%-- lock_acquire
                      |          |
                      |          |--21.82%-- _raw_spin_lock
                      |          |          |
                      |          |          |--37.26%-- unix_stream_recvmsg
                      |          |          |          sock_aio_read
                      |          |          |          do_sync_read
                      |          |          |          vfs_read
                      |          |          |          sys_read
                      |          |          |          system_call
                      |          |          |          __read
                      |          |          |
                      |          |          |--24.09%-- unix_stream_sendmsg
                      |          |          |          sock_aio_write
                      |          |          |          do_sync_write
                      |          |          |          vfs_write
                      |          |          |          sys_write
                      |          |          |          system_call
                      |          |          |          __write_nocancel

v2: Fix cfi annotations.
Reported-by: NSoeren Sandmann Pedersen <sandmann@redhat.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Jan Beulich <JBeulich@novell.com>

Prevent kprobes to probe on save_args() since this function
will be called from breakpoint exception handler. That will
cause infinit loop on breakpoint handling.
Signed-off-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: 2nddept-manager@sdl.hitachi.co.jp
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
LKML-Reference: <20101118101655.2779.2816.stgit@ltc236.sdl.hitachi.co.jp>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

gas prior to (perhaps) 2.16.90 has problems with passing non-
parenthesized expressions containing spaces to macros. Spaces, however,
get inserted by cpp between any macro expanding to a number and a
subsequent + or -. For the +, current x86 gas then removes the space
again (future gas may not do so), but for the - the space gets retained
and is then considered a separator between macro arguments.

Fix the respective definitions for both the - and + cases, so that they
neither contain spaces nor make cpp insert any (the latter by adding
seemingly redundant parentheses).
Signed-off-by: NJan Beulich <jbeulich@novell.com>
LKML-Reference: <4CBDBEBA020000780001E05A@vpn.id2.novell.com>
Cc: Alexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Provide a mechanism that allows running code in IRQ context. It is
most useful for NMI code that needs to interact with the rest of the
system -- like wakeup a task to drain buffers.

Perf currently has such a mechanism, so extract that and provide it as
a generic feature, independent of perf so that others may also
benefit.

The IRQ context callback is generated through self-IPIs where
possible, or on architectures like powerpc the decrementer (the
built-in timer facility) is set to generate an interrupt immediately.

Architectures that don't have anything like this get to do with a
callback from the timer tick. These architectures can call
irq_work_run() at the tail of any IRQ handlers that might enqueue such
work (like the perf IRQ handler) to avoid undue latencies in
processing the work.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NKyle McMartin <kyle@mcmartin.ca>
Acked-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>
[ various fixes ]
Signed-off-by: NHuang Ying <ying.huang@intel.com>
LKML-Reference: <1287036094.7768.291.camel@yhuang-dev>
Signed-off-by: NIngo Molnar <mingo@elte.hu>