Some firmwares may reboot CPUs with OS Double Lock set. Make sure that
it is unlocked, in order to use debug exceptions.

Cc: <stable@vger.kernel.org>
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

brk_handler() now looks pretty strange and can be refactored to drop its
funny 'handler_found' local variable altogether.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

kprobes and uprobes reserve some BRK immediates for installing their
probes. Define these along with the other reservations in brk-imm.h
and rename the ESR definitions to be consistent with the others that we
already have.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

Kprobes bypasses our debug hook registration code so that it doesn't
get tangled up with recursive debug exceptions from things like lockdep:

  http://lists.infradead.org/pipermail/linux-arm-kernel/2015-February/324385.html

However, since then, (a) the hook list has become RCU protected and (b)
the kprobes hooks were found not to filter out exceptions from userspace
correctly. On top of that, the step handler is invoked directly from
single_step_handler(), which *does* use the debug hook list, so it's
clearly not the end of the world.

For now, have kprobes use the debug hook registration API like everybody
else. We can revisit this in the future if this is found to limit
coverage significantly.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

Mixing kernel and user debug hooks together is highly error-prone as it
relies on all of the hooks to figure out whether the exception came from
kernel or user, and then to act accordingly.

Make our debug hook code a little more robust by maintaining separate
hook lists for user and kernel, with separate registration functions
to force callers to be explicit about the exception levels that they
care about.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

The comment next to the definition of our 'break_hook' list head is
at best wrong but mainly just meaningless. Rip it out.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

Since the 'addr' parameter contains an UNKNOWN value for non-watchpoint
debug exceptions, rename it to 'unused' for those hooks so we don't get
tempted to use it in the future.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

Wrap force_sig_fault with a helper that calls arm64_show_signal
and call arm64_force_sig_fault where appropraite.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

Every caller passes in current for tsk so there is no need to pass
tsk.  Instead make tsk a local variable initialized to current.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

Using arm64_force_sig_info means that printing messages about unhandled
signals is dealt with for us, so use that in preference to force_sig_info
and remove any homebrew printing code.

Signed-off-by: Will Deacon <will.deacon@arm.com>