linux-toradex.git/arch/arm/mm/alignment.c, branch v3.1.2

ARM: 7008/1: alignment: Make SIGBUS sent to userspace POSIXly correct

2011-08-09T07:42:39+00:00

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: Dave Martin 
Acked-by: Nicolas Pitre 
Acked-by: Kirill A. Shutemov 
Reviewed-by: Will Deacon 
Signed-off-by: Russell King

ARM: 7007/1: alignment: Prevent ignoring of faults with ARMv6 unaligned access model

2011-08-09T07:42:39+00:00

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: Dave Martin 
Acked-by: Nicolas Pitre 
Signed-off-by: Russell King

ARM: entry: avoid enabling interrupts in prefetch/data abort handlers

2011-07-02T09:56:00+00:00

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: Will Deacon 
Signed-off-by: Russell King

ARM: 6401/1: plug a race in the alignment trap handler

2010-09-23T14:17:04+00:00

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  for providing a test module
that made this issue reproducible.

Signed-off-by: Nicolas Pitre 
Signed-off-by: Russell King

ARM: 6268/1: ARMv6K and ARMv7 use fault statuses 3 and 6 as Access Flag fault

2010-07-27T09:48:41+00:00

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: Kirill A. Shutemov 
Signed-off-by: Russell King

ARM: 6269/1: Add 'code' parameter for hook_fault_code()

2010-07-27T09:48:34+00:00

Add one more parameter to hook_fault_code() to be able to set 'code'
field of struct fsr_info.

Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Russell King

ARM: 6252/1: Use SIGBUS for unaligned access instead of SIGILL

2010-07-27T09:43:49+00:00

POSIX specify to use signal SIGBUS with code BUS_ADRALN for invalid
address alignment.

Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Russell King

Merge branch 'devel-stable' into devel

2010-05-17T16:24:04+00:00

Conflicts:
	arch/arm/Kconfig
	arch/arm/include/asm/system.h
	arch/arm/mm/Kconfig

ARM: convert /proc/cpu/aligment to seq_file

2010-05-15T14:03:48+00:00

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
786d7e1612f0b0adb6046f19b906609e4fe8b1ba "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: Alexey Dobriyan 
Signed-off-by: Andrew Morton 
Signed-off-by: Russell King

ARM: fix build error in arch/arm/kernel/process.c

2010-04-21T07:45:21+00:00

/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: Russell King