system_call assembly code always pushes pointer to struct pt_regs as the
last additional parameter for all system calls. The only user of this
feature is xtensa_rt_sigreturn.
Avoid this special case. Define xtensa_rt_sigreturn as accepting no
argiments. Use current_pt_regs to get pointer to struct pt_regs in
xtensa_rt_sigreturn. Don't pass additional parameter from system_call
code.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Don't overwrite return value if system call was cancelled at entry by
ptrace. Return status code from do_syscall_trace_enter so that
pt_regs::syscall doesn't need to be changed to skip syscall.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

system_call saves and restores syscall number across system call to make
clone and execv entry and exit tracing match. This complicates things
when syscall code may be changed by ptrace.
Preserve syscall code in copy_thread and start_thread directly instead of
doing tricks in system_call.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Since the enabling and disabling of IRQs within preempt_schedule_irq()
is contained in a need_resched() loop, we don't need the outer arch
code loop.

Acked-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Message-Id: <20190923143620.29334-10-valentin.schneider@arm.com>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Provide a Kconfig choice to select whether only the default ABI, only
call0 ABI or both are supported. The default for XEA2 is windowed, but
it may change for XEA3. Call0 only runs userspace with PS.WOE disabled.
Supporting both windowed and call0 ABIs is tricky, as there's no
indication in the ELF binaries which ABI they use. So it is done by
probing: each process is started with PS.WOE disabled, but the handler
of an illegal instruction exception taken with PS.WOE retries faulting
instruction after enabling PS.WOE. It must happen before any signal is
delivered to the process, otherwise it may be delivered incorrectly.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

PS_WOE_BIT is mainly used to generate PS.WOE mask in the code. Introduce
PS_WOE_MASK macro and use it instead.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Provide abi_entry, abi_entry_default, abi_ret and abi_ret_default macros
that allocate aligned stack frame in windowed and call0 ABIs.
Provide XTENSA_SPILL_STACK_RESERVE macro that specifies required stack
frame size when register spilling is involved.
Replace all uses of 'entry' and 'retw' with the above macros.
This makes most of the xtensa assembly code ready for XEA3 and call0 ABI.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Syscall may alter pt_regs structure passed to it, resulting in a
mismatch between syscall entry end syscall exit entries in the ftrace.
Temporary restore syscall field of the pt_regs for the duration of
do_syscall_trace_leave.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Check whether calls to do_syscall_trace_{enter,leave} are necessary in
the system_call function. Define _TIF_WORK_MASK to a bitmask of flags
that reuire the calls. Fix comment.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

For the sake of clarity define macro NO_SYSCALL and use it for
setting/checking struct pt_regs::syscall field.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>