Adjust process management for both 32BIT and 64BIT, including: CPU
context switching, FPU loading/restoring, process dumping and process
tracing routines.

Q: Why modify switch.S?
A: LoongArch32 has no ldptr.d/stptr.d instructions, and asm offsets of
   thead_struct members are too large to be filled in the 12b immediate
   field of ld.w/st.w.

Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

When CONFIG_RANDSTRUCT enabled, members of task_struct are randomized.
There is a chance that TASK_STACK_CANARY be out of 12bit immediate's
range and causes build errors. TASK_STACK_CANARY is naturally aligned,
so fix it by replacing ld.d/st.d with ldptr.d/stptr.d which have 14bit
immediates.

Cc: stable@vger.kernel.org
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202511240656.0NaPcJs1-lkp@intel.com/
Suggested-by: Rui Wang <wangrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Correct the __switch_to() prototype in comments, keep it be the same as
the declaration in switch_to.h.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Add basic stack protector support similar to other architectures. A
constant canary value is set at boot time, and with help of compiler's
-fstack-protector we can detect stack corruption.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

The current LoongArch kernel stack is padded as if obeying the MIPS o32
calling convention (32 bytes), signifying the port's MIPS lineage but no
longer making sense. Remove the padding for clarity.

Reviewed-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

1. Use common arch_stack_walk() infrastructure to avoid duplicated code
   and avoid taking care of the stack storage and filtering.
2. Add sched_ra (means sched return address) and sched_cfa (means sched
   call frame address) to thread_info, and store them in switch_to().
3. Add __get_wchan() implementation.

Now we can print the process stack and wait channel by cat /proc/*/stack
and /proc/*/wchan.

Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Reflow the *.S files for better stylistic consistency, namely hard tabs
after mnemonic position, and vertical alignment of the first operand
with hard tabs. Tab width is obviously 8. Some pre-existing intra-block
vertical alignments are preserved.

Signed-off-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Add process management support for LoongArch, including: thread info
definition, context switch and process tracing.

Reviewed-by: WANG Xuerui <git@xen0n.name>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>