The push/pop instructions can be suboptimal when saving/restoring large
amounts of data to/from the stack, for example on entry/exit from the
kernel. This is because:

  (1) They act on descending addresses (i.e. the newly decremented sp),
      which may defeat some hardware prefetchers

  (2) They introduce an implicit dependency between each instruction, as
      the sp has to be updated in order to resolve the address of the
      next access.

This patch removes the push/pop instructions from our kernel entry/exit
macros in favour of ldp/stp plus offset.
Signed-off-by: NWill Deacon <will.deacon@arm.com>

Using an explicit adr instruction to set the link register to point at
ret_fast_syscall/ret_to_user can defeat branch and return stack predictors.

Instead, use the standard calling instructions (bl, blr) and have an
unconditional branch as the following instruction.
Signed-off-by: NWill Deacon <will.deacon@arm.com>

When returning from a debug exception taken from EL1, we unmask debug
exceptions after handling the exception. This is crucial for debug
exceptions taken from EL0, so that any kernel work on the ret_to_user
path can be debugged by kgdb.

However, when returning back to EL1 the only thing left to do is to
restore the original register state before the exception return. If
single-step has been enabled by the debug exception handler, we will
get stuck in an infinite debug exception loop, since we will take the
step exception as soon as we unmask debug exceptions.

This patch avoids unmasking debug exceptions on the debug exception
return path when the exception was taken from EL1.

Fixes: 2a283070 (arm64: debug: avoid accessing mdscr_el1 on fault paths where possible)
Cc: <stable@vger.kernel.org> #3.16+
Reported-by: NDavid Long <dave.long@linaro.org>
Reported-by: NAKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

This patch adds __NR_* definitions to asm/unistd32.h, moves the
__NR_compat_* definitions to asm/unistd.h and removes all the explicit
unistd32.h includes apart from the one building the compat syscall
table. The aim is to have the compat __NR_* definitions available but
without colliding with the native syscall definitions (required by
lib/compat_audit.c to avoid duplicating the audit header files between
native and compat).
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Make calls to ct_user_enter when the kernel is exited
and ct_user_exit when the kernel is entered (in el0_da,
el0_ia, el0_svc, el0_irq and all of the "error" paths).

These macros expand to function calls which will only work
properly if el0_sync and related code has been rearranged
(in a previous patch of this series).

The calls to ct_user_exit are made after hw debugging has been
enabled (enable_dbg_and_irq).

The call to ct_user_enter is made at the beginning of the
kernel_exit macro.

This patch is based on earlier work by Kevin Hilman.
Save/restore optimizations were also done by Kevin.
Acked-by: NWill Deacon <will.deacon@arm.com>
Reviewed-by: NKevin Hilman <khilman@linaro.org>
Tested-by: NKevin Hilman <khilman@linaro.org>
Signed-off-by: NLarry Bassel <larry.bassel@linaro.org>
Signed-off-by: NKevin Hilman <khilman@linaro.org>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

To implement the context tracker properly on arm64,
a function call needs to be made after debugging and
interrupts are turned on, but before the lr is changed
to point to ret_to_user(). If the function call
is made after the lr is changed the function will not
return to the correct place.

For similar reasons, defer the setting of x0 so that
it doesn't need to be saved around the function call
(save far_el1 in x26 temporarily instead).
Acked-by: NWill Deacon <will.deacon@arm.com>
Reviewed-by: NKevin Hilman <khilman@linaro.org>
Tested-by: NKevin Hilman <khilman@linaro.org>
Signed-off-by: NLarry Bassel <larry.bassel@linaro.org>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

The value of ESR has been stored into x1, and should be directly pass to
do_sp_pc_abort function, "MOV x1, x25" is an extra operation and do_sp_pc_abort
will get the wrong value of ESR.
Signed-off-by: NChiaHao <andy.jhshiu@gmail.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Cc: <stable@vger.kernel.org>

As done in arm, this change makes it easy to confirm we invoke syscall
related hooks, including syscall tracepoint, audit and seccomp which would
be implemented later, in correct order. That is, undoing operations in the
opposite order on exit that they were done on entry.
Acked-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NAKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Currently syscall_trace() is called only for ptrace.
With additional TIF_xx flags defined, it is now called in all the cases
of audit, ftrace and seccomp in addition to ptrace.
Acked-by: NRichard Guy Briggs <rgb@redhat.com>
Acked-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NAKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Since mdscr_el1 is part of the debug register group, it is highly likely
to be trapped by a hypervisor to prevent virtual machines from debugging
(buggering?) each other. Unfortunately, this absolutely destroys our
performance, since we access the register on many of our low-level
fault handling paths to keep track of the various debug state machines.

This patch removes our dependency on mdscr_el1 in the case that debugging
is not being used. More specifically we:

  - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and
    avoid disabling step in the MDSCR when we don't need to.
    MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from
    userspace.

  - Ensure debug exceptions are re-enabled on *all* exception entry
    paths, even the debug exception handling path (where we re-enable
    exceptions after invoking the handler). Since we can now rely on
    MDSCR_EL1.SS being cleared by the entry code, exception handlers can
    usually enable debug immediately before enabling interrupts.

  - Remove all debug exception unmasking from ret_to_user and
    el1_preempt, since we will never get here with debug exceptions
    masked.

This results in a slight change to kernel debug behaviour, where we now
step into interrupt handlers and data aborts from EL1 when debugging the
kernel, which is actually a useful thing to do. A side-effect of this is
that it *does* potentially prevent stepping off {break,watch}points when
there is a high-frequency interrupt source (e.g. a timer), so a debugger
would need to use either breakpoints or manually disable interrupts to
get around this issue.

With this patch applied, guest performance is restored under KVM when
debug register accesses are trapped (and we get a measurable performance
increase on the host on Cortex-A57 too).

Cc: Ian Campbell <ian.campbell@citrix.com>
Tested-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

If a task gets scheduled out and back in again and nothing has touched
its FPSIMD state in the mean time, there is really no reason to reload
it from memory. Similarly, repeated calls to kernel_neon_begin() and
kernel_neon_end() will preserve and restore the FPSIMD state every time.

This patch defers the FPSIMD state restore to the last possible moment,
i.e., right before the task returns to userland. If a task does not return to
userland at all (for any reason), the existing FPSIMD state is preserved
and may be reused by the owning task if it gets scheduled in again on the
same CPU.

This patch adds two more functions to abstract away from straight FPSIMD
register file saves and restores:
- fpsimd_restore_current_state -> ensure current's FPSIMD state is loaded
- fpsimd_flush_task_state -> invalidate live copies of a task's FPSIMD state
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>

Commit 64681787 (arm64: let the core code deal with preempt_count)
changed the code, but left the comments unchanged, fix it.
Signed-off-by: NNeil Zhang <zhangwm@marvell.com>
Acked-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

AArch64 Single Steping and Breakpoint debug exceptions will be
used by multiple debug framworks like kprobes & kgdb.

This patch implements the hooks for those frameworks to register
their own handlers for handling breakpoint and single step events.

Reworked the debug exception handler in entry.S: do_dbg to route
software breakpoint (BRK64) exception to do_debug_exception()
Signed-off-by: NSandeepa Prabhu <sandeepa.prabhu@linaro.org>
Signed-off-by: NDeepak Saxena <dsaxena@linaro.org>
Acked-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Commit f27dde8d (sched: Add NEED_RESCHED to the preempt_count)
introduced the use of bit 31 in preempt_count for obscure scheduling
purposes.

This causes interrupts taken from EL0 to hit the (open coded) BUG when
this flag is flipped while handling the interrupt (we compare the
values before and after, and kill the kernel if they are different).

The fix is to stop messing with the preempt count entirely, as this
is already being dealt with in the generic code (irq_enter/irq_exit).

Tested on a dual A53 FPGA running cyclictest.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

preempt_count is defined as an int. Oddly enough, we access it
as a 64bit value. Things become interesting when running a BE
kernel, and looking at the current CPU number, which is stored
as an int next to preempt_count. Like in a per-cpu interrupt
handler, for example...

Using a 32bit access fixes the issue for good.

Cc: Matthew Leach <matthew.leach@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

TCR.TBI0 can be used to cause hardware address translation to ignore the
top byte of userspace virtual addresses. Whilst not especially useful in
standard C programs, this can be used by JITs to `tag' pointers with
various pieces of metadata.

This patch enables this bit for AArch64 Linux, and adds a new file to
Documentation/arm64/ which describes some potential caveats when using
tagged virtual addresses.
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

do_undefinstr() has to be called with interrupts disabled since it may
read the instruction from the user address space which could lead to a
data abort and subsequent might_sleep() warning in do_page_fault().
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Written by Catalin Marinas, tested by APM on storm platform. This is needed
because of the failures encountered when running SpecWeb benchmark test.
Signed-off-by: NFeng Kan <fkan@apm.com>
Acked-by: NKumar Sankaran <ksankaran@apm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Currently, if a compat process reads or writes from/to a disabled
cp15/cp14 register, the trap is not handled by the el0_sync_compat
handler, and the kernel will head to bad_mode, where it will die(), and
oops(). For 64 bit processes, disabled system register accesses are
currently treated as unhandled instructions.

This patch modifies entry.S to treat these unhandled traps as undefined
instructions, sending a SIGILL to userspace. This gives processes a
chance to handle this and stop using inaccessible registers, and
prevents further issues in the kernel as a result of the die().
Reported-by: NJohannes Jensen <Johannes.Jensen@arm.com>
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

The ESR_EL1 decoding process is a bit cryptic, and KVM has also
a need for the same constants.

Add a new esr.h file containing the appropriate exception classes
constants, and change entry.S to use it. Fix a small bug in the
EL1 breakpoint check while we're at it.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

This macro is also useful to other bits defining vectors (hypervisor
stub, KVM...).

Move it to a common location.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

[fixes from Catalin Marinas folded]
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Tested-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

This patch converts the arm64 port to use the generic sys_execve()
implementation removing the arm64-specific (compat_)sys_execve_wrapper()
functions.
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

This patch enables CONFIG_GENERIC_KERNEL_EXECVE on arm64 and removes the
arm64-specific implementation of kernel_execve().
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

This patch enables CONFIG_GENERIC_KERNEL_THREAD on arm64, changes
copy_threads to cope with kernel threads creation and adapts
ret_from_fork accordingly. The arm64-specific kernel_thread
implementation is no longer needed.
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

This patch only includes asm/unistd32.h where necessary and removes its
inclusion in the asm/unistd.h file. The __SYSCALL_COMPAT guard is
dropped.
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Acked-by: NWill Deacon <will.deacon@arm.com>

task_work_run() implementation had the side effect of enabling
interrupts. With commit ac3d0da8 (task_work: Make task_work_add()
lockless), interrupts are no longer enabled revealing the bug in the
arch code. This patch enables the interrupt explicitly before calling
do_notify_resume().
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

The patch contains the exception entry code (kernel/entry.S), pt_regs
structure and related accessors, undefined instruction trapping and
stack tracing.

AArch64 Linux kernel (including kernel threads) runs in EL1 mode using
the SP1 stack. The vectors don't have a fixed address, only alignment
(2^11) requirements.
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Acked-by: NTony Lindgren <tony@atomide.com>
Acked-by: NNicolas Pitre <nico@linaro.org>
Acked-by: NOlof Johansson <olof@lixom.net>
Acked-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>