This adds a new kconfig and corresponding code to allow flushing
auto-refill data TLBs when page tables are swapped (e.g. during
context switching). This is mainly used to avoid multi-hit TLB
exception raised by certain memory access pattern. If memory is
only marked for user mode access but not inside a memory domain,
accessing that page in kernel mode would result in a TLB being
filled with kernel ASID. When going back into user mode, access
to the memory would result in another TLB being filled with
the user mode ASID. Now there are two entries on the same memory
page, and the multi-hit TLB exception will be raised if that
memory page is accessed. This type of access is better served
using memory partition and memory domain to share data. However,
this type of access is not prohibited but highly discouraged.
Wrapping the code in kconfig is simply because of the execution
penalty as there will be unnecessary TLB refilling being done.
So only enable this if necessary.
Fixes#88772
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
When looking for jump address in the syscall table, we need to
multiply the syscall ID by 4 before adding the address offset
of the beginning of the table. This is due to the jump address
being 32-bit (4 bytes). Instead of using two instructions to
shift the ID by 4 first and then the addition, we can use one
ADDX4 instruction to achieve the same result.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
Since the necessary register values are now pre-computed and
stored in the memory domain struct, we can use them directly
in various assembly locations, thus replacing the function
call to xtensa_swap_update_page_tables().
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
When syscall assembly is executed, the EPC points to the syscall
instruction, and we have to manually advance it so we will
return to the instruction after syscall to continue execution.
However, with zero-overhead loops and the syscall instruction is
the last instruction, this simple addition does not work as it
would point past the loop and would have skipped the loop.
Because of this, syscall entrance would need to look at the loop
registers and set the PC back to the beginning of loop if we are
still looping. Assuming most of the syscalls are not inside
loops, the extra handling code consumes quite a few cycles.
To workaround this, simply adds a nop after syscall so we no
longer have to deal with loops at syscall entrance, and that
a nop is faster than all the code to manipulate loop registers.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
In xtensa_userspace_enter, we were hard-coding to use level 2
interrupt return mechanism to pivot to user mode and start
running the user thread. However, EPC2 and EPS2 may be used
for other purposes, and they could be used for interrupt
return if there are only two level interrupts. So change
the userspace enter to use ZSR_RFI_LEVEL, ZSR_EPC and ZSR_EPS
instead to be more explicit.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
When returning from syscall, we cannot use RFE by using EPC1.
As there is no EPS1, we would need to write to PS before
returning. However, this creates a situation where interrupts
are being enabled (since PS is set), and any interrupts will
overwrite EPC1 before we return (which ensures chaos as we
would be returning to the wrong address). So utilize the same
mechanism as interrupt returning by use ZSR_EPS, ZSR_EPC and
ZSR_RFI_LEVEL.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
There is no need to do a jump to _syscall_returned as it is
the next to be run anyway. Keep the label there so we can
set breakpoint if needed.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
We stuff the 7th argument into stack by moving the stack pointer
before calling syscall handler. The Xtensa ABI says stack must
be 16-byte aligned. So instead of moving stack pointer 4 bytes,
we move 16 bytes (assuming stack has been aligned so far).
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
This moves the calculation of the return PC earlier in syscall
entry. There is no need to stash it into BSA, load it, do
the calculation and save it back. We can do the calculation
first and save it in BSA at the same time.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
We should not perform a straight OR operation on INTLEVEL as
we have no idea what existing PS.INTLEVEL is. Also, to avoid
any interferences, we disable interrupts very early during
syscall entrance. So we can remove the OR operation as
PS.INTLEVEL will still have all interrupts masked. Note that
we do not really need to OR PS_WOE into PS as we currently
only support windowed ABI which must have PS_WOE set in PS
anyway.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
This adds ODD_REG_RESTORE as a counterpart to ODD_REG_SAVE.
Both the code in interrupt handling and syscall exit have
been refactored to use this new macro.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
This adds two parameters for ODD_REG_SAVE for scratch register
and BSA pointer, thus allowing a bit more flexibility on how
it can be called.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
This removes the call to _xtensa_hifi_save() to save the HiFi
registers during syscalls. During syscall, we are not doing
context switching, and technically it is still the same thread.
There is no need to save HiFi registers.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
arch_user_string_nlen() did not exactly work correctly as any
invalid pointers being passed are de-referenced naively, which
results in DTLB misses (MMU) or access errors (MPU). However,
arch_user_string_nlen() should always return to the caller
with appropriate error code set, and should never result in
thread termination. Since we are usually going through syscalls
when arch_user_string_nlen() is called, for MMU, the DTLB miss
goes through double exception. Since the pointer is invalid,
there is a high chance there is not even a L2 page table
associated with that bad address. So the DTLB miss cannot be
handled and it just keeps looping in double exception until
there is another exception type where we get to the C handler.
However, the stack frame is no longer the frame associated
with the call to arch_user_string_nlen(), and the call return
address would be incorrect. Forcing this incorrect address as
the next PC would result in some other exceptions, e.g.
illegal instruction, which would go to the C handler again.
This time it will go to the end of handler and would result
in thread termination. For MPU systems, access errors would
simply result in thread terminal in the C handler. Because of
these reasons, change the arch_user_string_nlen() to check if
the memory region can be accessed under kernel mode first
before feeding it to strnlen().
Also remove the exception fixup arrays as there is nothing
there anymore.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
Namespaced the generated headers with `zephyr` to prevent
potential conflict with other headers.
Introduce a temporary Kconfig `LEGACY_GENERATED_INCLUDE_PATH`
that is enabled by default. This allows the developers to
continue the use of the old include paths for the time being
until it is deprecated and eventually removed. The Kconfig will
generate a build-time warning message, similar to the
`CONFIG_TIMER_RANDOM_GENERATOR`.
Updated the includes path of in-tree sources accordingly.
Most of the changes here are scripted, check the PR for more
info.
Signed-off-by: Yong Cong Sin <ycsin@meta.com>
- spill windows in the current context (before switching task) since
it will be erased.
- Remove unnucessary load/mov
Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>
For CPU without THREADPTR, we need an alternative way to figure
out if we are in user context. This extends the user context
check to do that via a brief syscall.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
Calling z_mrsh_* functions require 7 arguments where the 7th is
the stack frame. Only the first 6 arguments are passed by
registers where the 7th must be done via stack. However, this
is not being done and an incorrect argument was being passed to
the z_mrsh_* functions as stack frame pointer. An obvious issue
would be dumping of stack during kernel oops, as incorrect data
was being printed or crashes due to inaccessible memory. So fix
it by properly populating the stack with correct stack frame
pointer as outgoing argument for the caller of z_mrsh_*
functions.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
There is no need to do a call4 and jx. Simply do a callx4
is enough.
Also amended the now incorrect comment about how syscall
trampoline is set up. It is now a straight call4 instead of
the old 2x call4.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
Adds the necessary code required to unconditionally save/restore the
HiFi AE registers. The macros xchal_cp1_load and xchal_cp1_store
are defined in the Xtensa HAL.
Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>
Some Xtensa cores do not support NMI, so XCHAL_HAVE_NMI=0 and
XCHAL_NMILEVEL won't be defined at all causing
arch/xtensa/include/xtensa-asm2-s.h to throw compilation error.
Fixes: #67855
Signed-off-by: Maciej Kusio <maciejkusio@meta.com>
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
Simply to provide some consistencies on file naming under
arch/xtensa.
These are all internally used files and are not public.
So there is no need to provide a deprecation path for
them.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
Use thread local storage to check whether or not a thread is running
in user mode. This allows to use threadptr to properly support tls.
Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>
Userspace support for Xtensa architecture using Xtensa MMU.
Some considerations:
- Syscalls are not inline functions like in other architectures because
some compiler issues when using multiple registers to pass parameters
to the syscall. So here we have a function call so we can use
registers as we need.
- TLS is not supported by xcc in xtensa and reading PS register is
a privileged instruction. So, we have to use threadptr to know if a
thread is an user mode thread.
Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
