Adjust system call for both 32BIT and 64BIT, including: add the uapi
unistd_{32,64}.h and syscall_table_{32,64}.h inclusion, add sys_mmap2()
definition, change the system call entry routines, etc.

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

Add support for the stackleak feature. It initializes the stack with the
poison value before returning from system calls which improves the kernel
security.

At the same time, disables the plugin in EFI stub code because EFI stub
is out of scope for the protection.

Tested on Loongson-3A5000 (enable GCC_PLUGIN_STACKLEAK and LKDTM):
 # echo STACKLEAK_ERASING > /sys/kernel/debug/provoke-crash/DIRECT
 # dmesg
   lkdtm: Performing direct entry STACKLEAK_ERASING
   lkdtm: stackleak stack usage:
      high offset: 320 bytes
      current:     448 bytes
      lowest:      1264 bytes
      tracked:     1264 bytes
      untracked:   208 bytes
      poisoned:    14528 bytes
      low offset:  64 bytes
   lkdtm: OK: the rest of the thread stack is properly erased

Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch is the only architecture that calls syscall_exit_to_user_mode()
from assembly.

Move the call into C so that this function can be inlined across all
architectures.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250320-riscv_optimize_entry-v6-3-63e187e26041@rivosinc.com

The kernel CONFIG_UNWINDER_ORC option enables the ORC unwinder, which is
similar in concept to a DWARF unwinder. The difference is that the format
of the ORC data is much simpler than DWARF, which in turn allows the ORC
unwinder to be much simpler and faster.

The ORC data consists of unwind tables which are generated by objtool.
After analyzing all the code paths of a .o file, it determines information
about the stack state at each instruction address in the file and outputs
that information to the .orc_unwind and .orc_unwind_ip sections.

The per-object ORC sections are combined at link time and are sorted and
post-processed at boot time. The unwinder uses the resulting data to
correlate instruction addresses with their stack states at run time.

Most of the logic are similar with x86, in order to get ra info before ra
is saved into stack, add ra_reg and ra_offset into orc_entry. At the same
time, modify some arch-specific code to silence the objtool warnings.

Co-developed-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Jinyang He <hejinyang@loongson.cn>
Co-developed-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

As described in include/linux/linkage.h,

  FUNC -- C-like functions (proper stack frame etc.)
  CODE -- non-C code (e.g. irq handlers with different, special stack etc.)

  SYM_FUNC_{START, END} -- use for global functions
  SYM_CODE_{START, END} -- use for non-C (special) functions

So use SYM_CODE_* to annotate exception handlers.

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

KGDB is intended to be used as a source level debugger for the Linux
kernel. It is used along with gdb to debug a Linux kernel. GDB can be
used to "break in" to the kernel to inspect memory, variables and regs
similar to the way an application developer would use GDB to debug an
application. KDB is a frontend of KGDB which is similar to GDB.

By now, in addition to the generic KGDB features, the LoongArch KGDB
implements the following features:
- Hardware breakpoints/watchpoints;
- Software single-step support for KDB.

Signed-off-by: Qing Zhang <zhangqing@loongson.cn>   # Framework & CoreFeature
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn> # BreakPoint & SingleStep
Signed-off-by: Hui Li <lihui@loongson.cn>           # Some Minor Improvements
Signed-off-by: Randy Dunlap <rdunlap@infradead.org> # Some Build Error Fixes
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Some assembler symbols are not kprobe safe, such as handle_syscall (used
as syscall exception handler), *memset*/*memcpy*/*memmove* (may cause
recursive exceptions), they can not be instrumented, just blacklist them
for kprobing.

Here is a related problem and discussion:
Link: https://lore.kernel.org/lkml/20230114143859.7ccc45c1c5d9ce302113ab0a@kernel.org/

Tested-by: Jeff Xie <xiehuan09@gmail.com>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Let's start to kill la.abs in preparation for the subsequent support of
the PIE kernel.

BTW, Re-tab the indention in arch/loongarch/kernel/entry.S for alignment.

Signed-off-by: Xi Ruoyao <xry111@xry111.site>
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 system call support and related uaccess.h for LoongArch.

Q: Why keep _ARCH_WANT_SYS_CLONE definition while there is clone3:
A: The latest glibc release has some basic support for clone3 but it is
   not complete. E.g., pthread_create() and spawni() have converted to
   use clone3 but fork() will still use clone. Moreover, some seccomp
   related applications can still not work perfectly with clone3. E.g.,
   Chromium sandbox cannot work at all and there is no solution for it,
   which is more terrible than the fork() story [1].

[1] https://chromium-review.googlesource.com/c/chromium/src/+/2936184

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