xtensa: replace <asm-generic/export.h> with <linux/export.h>

Commit ddb5cdbafaaa ("kbuild: generate KSYMTAB entries by modpost")
deprecated <asm-generic/export.h>, which is now a wrapper of
<linux/export.h>.

Replace #include <asm-generic/export.h> with #include <linux/export.h>.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Message-Id: <20231126151222.1556761-1-masahiroy@kernel.org>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

xtensa: add asm-prototypes.h

Move assembly source prototypes from xtensa_ksyms.c to
asm/asm-prototypes.h, move corresponding EXPORT_SYMBOLs to the assembly
sources and enable HAVE_ASM_MODVERSIONS for xtensa.

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

xtensa: merge stack alignment definitions

xtensa currently has two different definitions for stack alignment.
Replace it with single definition usable in both C and assembly.

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

xtensa: add helpers for division, remainder and shifts

Don't rely on libgcc presence, build own versions of the helpers with
correct ABI.

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

xtensa: definitions for call0 ABI

Add assembly macros for calls, call arguments, preserved registers,
function entry and return for windowed and call0 ABIs.

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

xtensa: move fast exception handlers close to vectors

On XIP kernels it makes sense to have exception vectors and fast
exception handlers together (in a fast memory). In addition, with MTD
XIP support both vectors and fast exception handlers must be outside of
the FLASH.

Add section .exception.text and move fast exception handlers to it.
Put it together with vectors when vectors are outside of the .text.

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

xtensa: abstract 'entry' and 'retw' in assembly code

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>

xtensa: replace variant/core.h with asm/core.h

Introduce the header arch/xtensa/include/asm/core.h that provides
definitions for XCHAL macros missing in older xtensa releases. Use this
header instead of variant/core.h

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

xtensa: clean up word alignment macros in assembly code

Remove duplicate definitions of ALIGN/src_b/__src_b and SSA8/ssa8/__ssa8
from assembly sources and put single definition into asm/asmmacro.h

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

xtensa: clean up fixups in assembly code

Remove duplicate definitions of EX() and similar TRY/CATCH and SRC/DST
macros from assembly sources and put single definition into asm/asmmacro.h

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

xtensa: fixes for configs without loop option

Build-time fixes:
- make lbeg/lend/lcount save/restore conditional on kernel entry;
- don't clear lcount in platform_restart functions unconditionally.

Run-time fixes:
- use correct end of range register in __endla paired with __loopt, not
the unused temporary register. This fixes .bss zero-initialization.
Update comments in asmmacro.h;
- don't clobber a10 in the usercopy that leads to access to unmapped
memory.

Cc: <stable@vger.kernel.org>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

xtensa: move headers files to arch/xtensa/include

Move all header files for xtensa to arch/xtensa/include and platform and
variant header files to the appropriate arch/xtensa/platforms/ and
arch/xtensa/variants/ directories.

Moving the files gets also rid of all uses of symlinks in the Makefile.

This has been completed already for the majority of the architectures
and xtensa is one out of six missing.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Chris Zankel <chris@zankel.net>