Provide hooks into the kernel entry and exit paths to permit control
of userspace visibility to the kernel. The intended use is:
- on entry to kernel from user, uaccess_disable will be called to
disable userspace visibility
- on exit from kernel to user, uaccess_enable will be called to
enable userspace visibility
- on entry from a kernel exception, uaccess_save_and_disable will be
called to save the current userspace visibility setting, and disable
access
- on exit from a kernel exception, uaccess_restore will be called to
restore the userspace visibility as it was before the exception
occurred.
These hooks allows us to keep userspace visibility disabled for the
vast majority of the kernel, except for localised regions where we
want to explicitly access userspace.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Improve the do_ldrd_abort macro code - firstly, it inefficiently checks
for the LDRD encoding by doing a multi-stage test of various bits. This
can be simplified by generating a mask, bitmasking the instruction and
then comparing the result.
Secondly, we want to be able to test the result rather than branching
to do_DataAbort, so remove the branch at the end and rename the macro
to 'teq_ldrd' to reflect it's new usage. teq_ldrd macro returns 'eq'
if the instruction was a LDRD.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
The ARMv6 and ARMv7 early abort handlers clear the exclusive monitors
upon entry to the kernel, but this is redundant:
- We clear the monitors on every exception return since commit
200b812d00 ("Clear the exclusive monitor when returning from an
exception"), so this is not necessary to ensure the monitors are
cleared before returning from a fault handler.
- Any dummy STREX will target a temporary scratch area in memory, and
may succeed or fail without corrupting useful data. Its status value
will not be used.
- Any other STREX in the kernel must be preceded by an LDREX, which
will initialise the monitors consistently and will not depend on the
earlier state of the monitors.
Therefore we have no reason to care about the initial state of the
exclusive monitors when a data abort is taken, and clearing the monitors
prior to exception return (as we already do) is sufficient.
This patch removes the redundant clearing of the exclusive monitors from
the early abort handlers.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Add ARM_BE8() helper to wrap any code conditional on being
compile when CONFIG_ARM_ENDIAN_BE8 is selected and convert
existing places where this is to use it.
Acked-by: Nicolas Pitre <nico@linaro.org>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Erratum #326103 ("FSR write bit incorrect on a SWP to read-only memory")
only affects the ARM 1136 core prior to r1p0. The workaround
disassembles the faulting instruction to determine whether it was a read
or write access on all v6 cores.
An issue has been reported on the ARM 11MPCore whereby loading the
faulting instruction may happen in parallel with that page being
unmapped, resulting in a deadlock due to the lack of TLB broadcasting
in hardware:
http://lists.infradead.org/pipermail/linux-arm-kernel/2012-March/091561.html
This patch limits the workaround so that it is only used on affected
cores, which are known to be UP only. Other v6 cores can rely on the
FSR to indicate the access type correctly.
Cc: stable@vger.kernel.org
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Tail-call the main C data abort handler code from the per-CPU helper
code. Update the comments in the code wrt the new calling and return
register state.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This allows us to pass the pt_regs pointer in to these functions
ready for tail-calling the abort handler.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Require all callers of abort macros to specify the registers to be
used. This improves the documentation at the callsites as to which
registers are being used by this assembly code.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
If CONFIG_CPU_V6 is enabled, then the kernel must support ARMv6 CPUs
which don't have the V6K extensions implemented. Always use the
dummy store-exclusive method to ensure that the exclusive monitors are
cleared.
If CONFIG_CPU_V6 is not set, but CONFIG_CPU_32v6K is enabled, then we
have the K extensions available on all CPUs we're building support for,
so we can use the new clear-exclusive instruction.
Acked-by: Tony Lindgren <tony@atomide.com>
Tested-by: Sourav Poddar <sourav.poddar@ti.com>
Tested-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Starting with ARMv6, the CPUs support the BE-8 variant of big-endian
(byte-invariant). This patch adds the core support:
- setting of the BE-8 mode via the CPSR.E register for both kernel and
user threads
- big-endian page table walking
- REV used to rotate instructions read from memory during fault
processing as they are still little-endian format
- Kconfig and Makefile support for BE-8. The --be8 option must be passed
to the final linking stage to convert the instructions to
little-endian
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Because of an ARM1136 erratum (326103), the current v6_early_abort
function needs to set the correct FSR[11] value which determines whether
the data abort was caused by a read or write. For legacy reasons (bit 10
not handled by software), bit 10 was also cleared masking out imprecise
aborts on ARMv6 CPUs. This patch removes the clearing of bit 10 of FSR.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
The target of the strex instruction to clear the exlusive monitor
is currently the top of the stack. If the store succeeeds this
corrupts r0 in pt_regs. Use the next stack location instead of
the current one to prevent any chance of corrupting an in-use
address.
Signed-off-by: Seth Forshee <seth.forshee@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Patch from Catalin Marinas
Data abort caused by ldrex/strex can leave the exclusive monitor in an
unpredictable state. It is recommended that a clrex/strex is performed to
clear this state.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Patch from George G. Davis
As noted in http://www.arm.com/linux/patch-2.6.9-arm1.gz, the "Faulty SWP instruction on 1136 doesn't set bit 11 in DFSR." So the v6_early_abort handler does not report the correct rd/wr direction for the SWP instruction which may result in SEGVS or hangs. In order to work around this problem, this patch merely updates the fix contained in the ARM Ltd. patch to use the macroised abort handler fixups.
Signed-off-by: George G. Davis
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Russell King