I noticed on some of my systems that page fault tracing doesn't
work:

	cd /sys/kernel/debug/tracing
	echo 1 > events/exceptions/enable
	cat trace;
	# nothing shows up

I eventually traced it down to CONFIG_KVM_GUEST.  At least in a
KVM VM, enabling that option breaks page fault tracing, and
disabling fixes it.  I tried on some old kernels and this does
not appear to be a regression: it never worked.

There are two page-fault entry functions today.  One when tracing
is on and another when it is off.  The KVM code calls do_page_fault()
directly instead of calling the traced version:

> dotraplinkage void __kprobes
> do_async_page_fault(struct pt_regs *regs, unsigned long
> error_code)
> {
>         enum ctx_state prev_state;
>
>         switch (kvm_read_and_reset_pf_reason()) {
>         default:
>                 do_page_fault(regs, error_code);
>                 break;
>         case KVM_PV_REASON_PAGE_NOT_PRESENT:

I'm also having problems with the page fault tracing on bare
metal (same symptom of no trace output).  I'm unsure if it's
related.

Steven had an alternative to this which has zero overhead when
tracing is off where this includes the standard noops even when
tracing is disabled.  I'm unconvinced that the extra complexity
of his apporach:

	http://lkml.kernel.org/r/20140508194508.561ed220@gandalf.local.home

is worth it, expecially considering that the KVM code is already
making page fault entry slower here.  This solution is
dirt-simple.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86@kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NDave Hansen <dave.hansen@linux.intel.com>
Acked-by: N"H. Peter Anvin" <hpa@zytor.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Trivial, make math_error() static.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>

Use NOKPROBE_SYMBOL macro for protecting functions
from kprobes instead of __kprobes annotation under
arch/x86.

This applies nokprobe_inline annotation for some cases,
because NOKPROBE_SYMBOL() will inhibit inlining by
referring the symbol address.

This just folds a bunch of previous NOKPROBE_SYMBOL()
cleanup patches for x86 to one patch.
Signed-off-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Link: http://lkml.kernel.org/r/20140417081814.26341.51656.stgit@ltc230.yrl.intra.hitachi.co.jp
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fernando Luis Vázquez Cao <fernando_b1@lab.ntt.co.jp>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Lebon <jlebon@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Matt Fleming <matt.fleming@intel.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

This patch registers exception handlers for tracing to a trace IDT.

To implemented it in set_intr_gate(), this patch does followings.
 - Register the exception handlers to
   the trace IDT by prepending "trace_" to the handler's names.
 - Also, newly introduce trace_page_fault() to add tracepoints
   in a subsequent patch.
Signed-off-by: NSeiji Aguchi <seiji.aguchi@hds.com>
Link: http://lkml.kernel.org/r/52716DEC.5050204@hds.comSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Mark 32bit dotraplinkage functions as __visible for LTO.
64bit already is using asmlinkage which includes it.

v2: Clean up (M.Marek)
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1375740170-7446-3-git-send-email-andi@firstfloor.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

The traps are referred to by their numbers and it can be difficult to
understand them while reading the code without context. This patch adds
enumeration of the trap numbers and replaces the numbers with the correct
enum for x86.
Signed-off-by: NKees Cook <keescook@chromium.org>
Link: http://lkml.kernel.org/r/20120310000710.GA32667@www.outflux.netSigned-off-by: NH. Peter Anvin <hpa@zytor.com>

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>

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>

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>

The only difference between FPU and SIMD exceptions is where the
status bits are read from (cwd/swd vs. mxcsr).  This also fixes
the discrepency introduced by commit adf77bac, which fixed FPU
but not SIMD.
Signed-off-by: NBrian Gerst <brgerst@gmail.com>
LKML-Reference: <1269176446-2489-3-git-send-email-brgerst@gmail.com>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

patch_espfix_desc() is not used after commit
dc4c2a0aSigned-off-by: NAkinobu Mita <akinobu.mita@gmail.com>
LKML-Reference: <20090718150955.GB11294@localhost.localdomain>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Native x86-64 uses the IST mechanism to run int3 and debug traps on
an alternative stack.  Xen does not do this, and so the frames were
being misinterpreted by the ptrace code.  This change special-cases
these two exceptions by using Xen variants which run on the normal
kernel stack properly.

Impact: avoid crash or bad data when IST trap is invoked under Xen
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

Impact: cleanup

asm/stacktrace.h is more appropriate so removing other 2 declarations.
Signed-off-by: NJaswinder Singh Rajput <jaswinderrajput@gmail.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
LKML-Reference: <1239695308.3033.34.camel@ht.satnam>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: cleanup

Eliminate more than 20 unnecessary #include lines in fault.c

Also fix include file dependency bug in asm/traps.h. (this was
masked before, by implicit inclusion)
Signed-off-by: NIngo Molnar <mingo@elte.hu>
LKML-Reference: <tip-56aea8468746e673a4bf50b6a13d97b2d1cbe1e8@git.kernel.org>
Acked-by: NH. Peter Anvin <hpa@linux.intel.com>

The generic exception handler (error_code) passes in the pt_regs
pointer and the error code (unused in this case).  The commit
"x86: fix math_emu register frame access" changed this to pass by
value, which doesn't work correctly with stack protector enabled.
Change it back to use the pt_regs pointer.
Signed-off-by: NBrian Gerst <brgerst@gmail.com>
Acked-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

do_device_not_available() is the handler for #NM and it declares that
it takes a unsigned long and calls math_emu(), which takes a long
argument and surprisingly expects the stack frame starting at the zero
argument would match struct math_emu_info, which isn't true regardless
of configuration in the current code.

This patch makes do_device_not_available() take struct pt_regs like
other exception handlers and initialize struct math_emu_info with
pointer to it and pass pointer to the math_emu_info to math_emulate()
like normal C functions do.  This way, unless gcc makes a copy of
struct pt_regs in do_device_not_available(), the register frame is
correctly accessed regardless of kernel configuration or compiler
used.

This doesn't fix all math_emu problems but it at least gets it
somewhat working.
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: cleanup

 In asm/traps.h :-
 do_double_fault : added under X86_64
 sync_regs : added under X86_64
 math_error : moved out from X86_32 as it is common for both 32 and 64 bit
 math_emulate : moved from X86_32 as it is common for both 32 and 64 bit
 smp_thermal_interrupt : added under X86_64
 mce_threshold_interrupt : added under X86_64
Signed-off-by: NJaswinder Singh <jaswinder@infradead.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Change header guards named "ASM_X86__*" to "_ASM_X86_*" since:

a. the double underscore is ugly and pointless.
b. no leading underscore violates namespace constraints.
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

Mark the exception handlers with "dotraplinkage" to hide the
calling convention differences between i386 and x86_64.
Signed-off-by: NAlexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Split out math_error from do_coprocessor_error and simd_math_error
from do_simd_coprocessor_error, like on i386. While at it, add the
"error_code" parameter to do_coprocessor_error, do_simd_coprocessor_error
and do_spurious_interrupt_bug.

This does not change the generated code, but brings the declarations in
line with all the other trap handlers.
Signed-off-by: NAlexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

fix build breakage, missing header file.
Signed-off-by: NSrinivasa DS <srinivasa@in.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Currently a SIGTRAP can denote any one of below reasons.
	- Breakpoint hit
	- H/W debug register hit
	- Single step
	- Signal sent through kill() or rasie()

Architectures like powerpc/parisc provides infrastructure to demultiplex
SIGTRAP signal by passing down the information for receiving SIGTRAP through
si_code of siginfot_t structure. Here is an attempt is generalise this
infrastructure by extending it to x86 and x86_64 archs.
Signed-off-by: NSrinivasa DS <srinivasa@in.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: akpm@linux-foundation.org
Cc: paulus@samba.org
Cc: linuxppc-dev@ozlabs.org
Signed-off-by: NIngo Molnar <mingo@elte.hu>

declared do_page_fault() in asm-x86/trap.h for both X86_32 and X86_64

removed do_invalid_op declaration from mm/fault.c as it is already declared in asm-x86/trap.h
Signed-off-by: NJaswinder Singh <jaswinder@infradead.org>

This patch is the result of an automatic script that consolidates the
format of all the headers in include/asm-x86/.

The format:

1. No leading underscore. Names with leading underscores are reserved.
2. Pathname components are separated by two underscores. So we can
   distinguish between mm_types.h and mm/types.h.
3. Everything except letters and numbers are turned into single
   underscores.
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

Declaring x86 traps under one hood.
Declaring x86 do_traps before defining them.
Signed-off-by: NJaswinder Singh <jaswinder@infradead.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Alexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: NIngo Molnar <mingo@elte.hu>