Save and report (via the procfs file) the last kernel unaligned fault
location.  This allows us to trivially inspect where the last fault
happened for cases which we don't expect to occur.

Since we expect the kernel to generate misalignment faults (due to
the networking layer), even when warnings are enabled, we don't log
them for the kernel.
Tested-by: NTony Lindgren <tony@atomide.com>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

cr_no_alignment is really only used by the alignment code.  Since we no
longer change the setting of cr_alignment after boot, we can localise
this to alignment.c
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

alignment.c will not be built unless CPU_CP15 is set:

config CPU_CP15
        bool

config CPU_CP15_MMU
        bool
        select CPU_CP15

config ALIGNMENT_TRAP
        bool
        depends on CPU_CP15_MMU

So there's no point having conditionals on CPU_CP15 within this code.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Keep all bits of alignment handling together.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Several places open-code this manipulation, let's consolidate this.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Rather than reading the cr_alignment variable, use get_cr() to read
directly from the hardware instead.  We have two places where this
occurs, neither of them are performance critical.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

If we are in BE8 mode, we must deal with the instruction stream being
in LE order when data is being loaded in BE order. Ensure the data is
swapped before processing to avoid thre following:

Change to using <asm/opcodes.h> to provide the necessary conversion
functions to change the byte ordering.

This stops the following warning messages from the kernel on a fault:

Unhandled fault: alignment exception (0x001) at 0xbfa09567
Alignment trap: not handling instruction 030091e8 at [<80333e8c>]
Signed-off-by: NBen Dooks <ben.dooks@codethink.co.uk>
Reviewed-by: NDave Martin <Dave.Martin@arm.com>
Tested-by: NThomas Petazzoni <thomas.petazzoni@free-electrons.com>

Paolo Pisati reports that IPv6 triggers this warning:

BUG: scheduling while atomic: swapper/0/0/0x40000100
Modules linked in:
[<c001b1c4>] (unwind_backtrace+0x0/0xf0) from [<c0503c5c>] (__schedule_bug+0x48/0x5c)
[<c0503c5c>] (__schedule_bug+0x48/0x5c) from [<c0508608>] (__schedule+0x700/0x740)
[<c0508608>] (__schedule+0x700/0x740) from [<c007007c>] (__cond_resched+0x24/0x34)
[<c007007c>] (__cond_resched+0x24/0x34) from [<c05086dc>] (_cond_resched+0x3c/0x44)
[<c05086dc>] (_cond_resched+0x3c/0x44) from [<c0021f6c>] (do_alignment+0x178/0x78c)
[<c0021f6c>] (do_alignment+0x178/0x78c) from [<c00083e0>] (do_DataAbort+0x34/0x98)
[<c00083e0>] (do_DataAbort+0x34/0x98) from [<c0509a60>] (__dabt_svc+0x40/0x60)
Exception stack(0xc0763d70 to 0xc0763db8)
3d60:                                     e97e805e e97e806e 2c000000 11000000
3d80: ea86bb00 0000002c 00000011 e97e807e c076d2a8 e97e805e e97e806e 0000002c
3da0: 3d000000 c0763dbc c04b98fc c02a8490 00000113 ffffffff
[<c0509a60>] (__dabt_svc+0x40/0x60) from [<c02a8490>] (__csum_ipv6_magic+0x8/0xc8)

Fix this by using probe_kernel_address() stead of __get_user().

Cc: <stable@vger.kernel.org>
Reported-by: NPaolo Pisati <p.pisati@gmail.com>
Tested-by: NPaolo Pisati <p.pisati@gmail.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

This makes cr_alignment a constant 0 to break code that tries to modify
the value as it's likely that it's built on wrong assumption when
CONFIG_CPU_CP15 isn't defined. For code that is only reading the value 0
is more or less a fine value to report.
Signed-off-by: NUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Message-Id: 1358413196-5609-2-git-send-email-u.kleine-koenig@pengutronix.de (v8)

The variables here are really not used uninitialized.

arch/arm/mm/alignment.c: In function 'do_alignment':
arch/arm/mm/alignment.c:327:15: warning: 'offset.un' may be used uninitialized in this function [-Wmaybe-uninitialized]
arch/arm/mm/alignment.c:748:21: note: 'offset.un' was declared here
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

One such warning was recently fixed in a761cebf "ARM: Fix build warning
in arch/arm/mm/alignment.c" but only for the thumb2 case, this fixes
the other half.

arch/arm/mm/alignment.c: In function 'do_alignment':
arch/arm/mm/alignment.c:327:15: error: 'offset.un' may be used uninitialized in this function
arch/arm/mm/alignment.c:748:21: note: 'offset.un' was declared here
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>

Fix this harmless build warning:

arch/arm/mm/alignment.c: In function 'do_alignment':
arch/arm/mm/alignment.c:749:21: warning: 'offset.un' may be used uninitialized in this function

This is caused by the compiler not being able to properly analyse the
code to prove that offset.un is assigned in every case.  The case it
struggles with is where we assign the handler from the Thumb parser -
do_alignment_t32_to_handler().  As this starts by zeroing this variable
via a pointer, move it into the calling function.  This fixes the
warning.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Disintegrate asm/system.h for ARM.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
cc: Russell King <linux@arm.linux.org.uk>
cc: linux-arm-kernel@lists.infradead.org

Avoid namespace conflicts with drivers over the CP15 definitions by
moving CP15 related prototypes and definitions to a private header
file.
Acked-by: NStephen Warren <swarren@nvidia.com>
Tested-by: Stephen Warren <swarren@nvidia.com> [Tegra]
Acked-by: NH Hartley Sweeten <hsweeten@visionengravers.com>
Tested-by: H Hartley Sweeten <hsweeten@visionengravers.com> [EP93xx]
Acked-by: NNicolas Pitre <nico@linaro.org>
Acked-by: NKukjin Kim <kgene.kim@samsung.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Avoid namespace conflicts with drivers over the CP15 definitions by
moving CP15 related prototypes and definitions to a private header
file.
Acked-by: NStephen Warren <swarren@nvidia.com>
Tested-by: Stephen Warren <swarren@nvidia.com> [Tegra]
Acked-by: NH Hartley Sweeten <hsweeten@visionengravers.com>
Tested-by: H Hartley Sweeten <hsweeten@visionengravers.com> [EP93xx]
Acked-by: NNicolas Pitre <nico@linaro.org>
Acked-by: NKukjin Kim <kgene.kim@samsung.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

The DFSR and IFSR register format is different when LPAE is enabled. In
addition, DFSR and IFSR have similar definitions for the fault type.
This modifies the fault code to correctly handle the new format.
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

The two functions cpu_is_v6_unaligned and safe_usermode
are only defined when CONFIG_PROC_FS is enabled, but
are used outside of the #ifdef.
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Cc: Dave Martin <dave.martin@linaro.org>

With the UM_SIGNAL alignment fault mode, no siginfo structure is
passed to userspace.

POSIX specifies how siginfo_t should be populated for alignment
faults, so this patch does just that:

  * si_signo = SIGBUS
  * si_code = BUS_ADRALN
  * si_addr = misaligned data address at which access was attempted
Signed-off-by: NDave Martin <dave.martin@linaro.org>
Acked-by: NNicolas Pitre <nicolas.pitre@linaro.org>
Acked-by: NKirill A. Shutemov <kirill@shutemov.name>
Reviewed-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Currently, it's possible to set the kernel to ignore alignment
faults when changing the alignment fault handling mode at runtime
via /proc/sys/alignment, even though this is undesirable on ARMv6
and above, where it can result in infinite spins where an un-fixed-
up instruction repeatedly faults.

In addition, the kernel clobbers any alignment mode specified on
the command-line if running on ARMv6 or above.

This patch factors out the necessary safety check into a couple of
new helper functions, and checks and modifies the fault handling
mode as appropriate on boot and on writes to /proc/cpu/alignment.

Prior to ARMv6, the behaviour is unchanged.

For ARMv6 and above, the behaviour changes as follows:

  * Attempting to ignore faults on ARMv6 results in the mode being
    forced to UM_FIXUP instead.  A warning is printed if this
    happened as a result of a write to /proc/cpu/alignment.  The
    user's UM_WARN bit (if present) is still honoured.

  * An alignment= argument from the kernel command-line is now
    honoured, except that the kernel will modify the specified mode
    as described above.  This is allows modes such as UM_SIGNAL and
    UM_WARN to be active immediately from boot, which is useful for
    debugging purposes.
Signed-off-by: NDave Martin <dave.martin@linaro.org>
Acked-by: NNicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Avoid enabling interrupts if the parent context had interrupts enabled
in the abort handler assembly code, and move this into the breakpoint/
page/alignment fault handlers instead.

This gets rid of some special-casing for the breakpoint fault handlers
from the low level abort handler path.
Acked-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

When the policy for user space is to ignore misaligned accesses from user
space, the processor then performs a documented rotation on the accessed
data.  This is the result of the access being trapped, and the kernel
disabling the alignment trap before returning to user space again.

In kernel space we always want misaligned accesses to be fixed up.  This
is enforced by always re-enabling the alignment trap on every entry into
kernel space from user space.  No such re-enabling is performed when an
exception occurs while already in kernel space as the alignment trap is
always supposed to be enabled in that case.

There is however a small race window when a misaligned access in user
space is trapped and the alignment trap disabled, but the CPU didn't
return to user space just yet.  Any exception would be entered from kernel
space at that point and the kernel would then execute with the alignment
trap disabled.

Thanks to Maxime Bizon <mbizon@freebox.fr> for providing a test module
that made this issue reproducible.
Signed-off-by: NNicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Statuses 3 (0b00011) and 6 (0x00110) of DFSR are Access Flags faults on
ARMv6K and ARMv7. Let's patch fsr_info[] at runtime if we are on ARMv7
or later.

Unfortunately, we don't have runtime check for 'K' extension, so we
can't check for it.
Signed-off-by: NKirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Add one more parameter to hook_fault_code() to be able to set 'code'
field of struct fsr_info.
Signed-off-by: NKirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

POSIX specify to use signal SIGBUS with code BUS_ADRALN for invalid
address alignment.
Signed-off-by: NKirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Convert code away from ->read_proc/->write_proc interfaces.  Switch to
proc_create()/proc_create_data() which makes addition of proc entries
reliable wrt NULL ->proc_fops, NULL ->data and so on.

Problem with ->read_proc et al is described here commit
786d7e16 "Fix rmmod/read/write races in
/proc entries"

This patch is part of an effort to remove the old simple procfs PAGE_SIZE
buffer interface.
Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

/tmp/ccJ3ssZW.s: Assembler messages:
/tmp/ccJ3ssZW.s:1952: Error: can't resolve `.text' {.text section} - `.LFB1077'

This is caused because:

	.section .data
	.section .text
	.section .text
	.previous

does not return us to the .text section, but the .data section; this
makes use of .previous dangerous if the ordering of previous sections
is not known.

Fix up the other users of .previous; .pushsection and .popsection are
a safer pairing to use than .section and .previous.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Some glibc versions intentionally create lots of alignment faults in
their gconv code, which if not fixed up, results in segfaults during
boot.  This can prevent systems booting properly.

There is no clear hard-configurable default for this; the desired
default depends on the nature of the userspace which is going to be
booted.

So, provide a way for the alignment fault handler to be configured via
the kernel command line.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Always creating this directory avoids other users having to jump
through silly hoops when they want to share this directory.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

This patch adds the ARM/Thumb-2 unified support to the arch/arm/mm/*
files.
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

From: Min Zhang <mzhang@mvista.com>

Add alignment fault fixup support for 32-bit Thumb-2 LDM, LDRD, POP,
PUSH, STM and STRD instructions.  Alignment fault fixup support for
the remaining 32-bit Thumb-2 load/store instruction cases is not
included since ARMv6 and later processors include hardware support
for loads and stores of unaligned words and halfwords.
Signed-off-by: NMin Zhang <mzhang@mvista.com>
Signed-off-by: NGeorge G. Davis <gdavis@mvista.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

On ARMv6 and later CPUs, it is possible for userspace processes to
get stuck on a misaligned load or store due to the "ignore fault"
setting; unlike previous CPUs, retrying the instruction without
the 'A' bit set does not always cause the load to succeed.

We have no real option but to default to fixing up alignment faults
on these CPUs, and having the CPU fix up those misaligned accesses
which it can.
Reported-by: NWolfgang Grandegger <wg@grandegger.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

... and fix those drivers that were incorrectly relying upon
that include.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

One of the easiest things to isolate is the pid printed in kernel log.
There was a patch, that made this for arch-independent code, this one makes
so for arch/xxx files.

It took some time to cross-compile it, but hopefully these are all the
printks in arch code.
Signed-off-by: NAlexey Dobriyan <adobriyan@openvz.org>
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fix various bits of obviously-busted code which we're not happening to
compile, due to ifdefs.

Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Jeff Garzik <jeff@garzik.org>
Cc: Jan Kara <jack@ucw.cz>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Spelling fixes in arch/arm/.
Signed-off-by: NSimon Arlott <simon@fire.lp0.eu>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Lots of places in arch/arm were needlessly including linux/ptrace.h,
resumably because we used to pass a struct pt_regs to interrupt
handlers.  Now that we don't, all these ptrace.h includes are
redundant.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Since do_bad_area() always takes the currently active task and
(supposed to) take the currently active MM, there's no point passing
them to this function.  Instead, obtain references to them inside
do_bad_area().
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Signed-off-by: NJörn Engel <joern@wohnheim.fh-wedel.de>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>

Patch from George G. Davis

Fix leading, trailing and other miscellaneous whitespace issues
in arch/arm/kernel/alignment.c.
Signed-off-by: NGeorge G. Davis <gdavis@mvista.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>