[PATCH v2] LoongArch: Remove unused kernel stack padding

[Jinyang He]

Kernel stack padding looks like obey MIPS o32 Calling Convention, as
LoongArch is inspired by MIPS and keep it. Remove it avoid not clear
code.

Link: https://lore.kernel.org/loongarch/1662130897-13156-1-git-send-email-hejinyang@xxxxxxxxxxx/

Signed-off-by: Jinyang He <hejinyang@xxxxxxxxxxx>
---
 v2: Remove TOP_OF_KERNEL_STACK_PADDING
     Remove 'init stack pointer' in head.S

 arch/loongarch/include/asm/processor.h | 2 +-
 arch/loongarch/include/asm/ptrace.h    | 2 +-
 arch/loongarch/kernel/head.S           | 3 +--
 arch/loongarch/kernel/process.c        | 4 ++--
 arch/loongarch/kernel/switch.S         | 2 +-
 5 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/arch/loongarch/include/asm/processor.h b/arch/loongarch/include/asm/processor.h
index 1c4b4308378d..780e0d39f638 100644
--- a/arch/loongarch/include/asm/processor.h
+++ b/arch/loongarch/include/asm/processor.h
@@ -194,7 +194,7 @@ static inline void flush_thread(void)
 unsigned long __get_wchan(struct task_struct *p);
 
 #define __KSTK_TOS(tsk) ((unsigned long)task_stack_page(tsk) + \
-			 THREAD_SIZE - 32 - sizeof(struct pt_regs))
+			 THREAD_SIZE - sizeof(struct pt_regs))
 #define task_pt_regs(tsk) ((struct pt_regs *)__KSTK_TOS(tsk))
 #define KSTK_EIP(tsk) (task_pt_regs(tsk)->csr_era)
 #define KSTK_ESP(tsk) (task_pt_regs(tsk)->regs[3])
diff --git a/arch/loongarch/include/asm/ptrace.h b/arch/loongarch/include/asm/ptrace.h
index 17838c6b7ccd..82649a78fec1 100644
--- a/arch/loongarch/include/asm/ptrace.h
+++ b/arch/loongarch/include/asm/ptrace.h
@@ -133,7 +133,7 @@ static inline void die_if_kernel(const char *str, struct pt_regs *regs)
 #define current_pt_regs()						\
 ({									\
 	unsigned long sp = (unsigned long)__builtin_frame_address(0);	\
-	(struct pt_regs *)((sp | (THREAD_SIZE - 1)) + 1 - 32) - 1;	\
+	(struct pt_regs *)((sp | (THREAD_SIZE - 1)) + 1) - 1;		\
 })
 
 /* Helpers for working with the user stack pointer */
diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
index 4d352230fbc3..0e1752fbc857 100644
--- a/arch/loongarch/kernel/head.S
+++ b/arch/loongarch/kernel/head.S
@@ -81,10 +81,9 @@ SYM_CODE_START(kernel_entry)			# kernel entry point
 
 	la.pcrel	tp, init_thread_union
 	/* Set the SP after an empty pt_regs.  */
-	PTR_LI		sp, (_THREAD_SIZE - 32 - PT_SIZE)
+	PTR_LI		sp, (_THREAD_SIZE - PT_SIZE)
 	PTR_ADD		sp, sp, tp
 	set_saved_sp	sp, t0, t1
-	PTR_ADDI	sp, sp, -4 * SZREG	# init stack pointer
 
 	bl		start_kernel
 
diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c
index 660492f064e7..dae087d6c458 100644
--- a/arch/loongarch/kernel/process.c
+++ b/arch/loongarch/kernel/process.c
@@ -129,7 +129,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	unsigned long clone_flags = args->flags;
 	struct pt_regs *childregs, *regs = current_pt_regs();
 
-	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
+	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
 
 	/* set up new TSS. */
 	childregs = (struct pt_regs *) childksp - 1;
@@ -236,7 +236,7 @@ bool in_task_stack(unsigned long stack, struct task_struct *task,
 			struct stack_info *info)
 {
 	unsigned long begin = (unsigned long)task_stack_page(task);
-	unsigned long end = begin + THREAD_SIZE - 32;
+	unsigned long end = begin + THREAD_SIZE;
 
 	if (stack < begin || stack >= end)
 		return false;
diff --git a/arch/loongarch/kernel/switch.S b/arch/loongarch/kernel/switch.S
index 43ebbc3990f7..202a163cb32f 100644
--- a/arch/loongarch/kernel/switch.S
+++ b/arch/loongarch/kernel/switch.S
@@ -26,7 +26,7 @@ SYM_FUNC_START(__switch_to)
 	move	tp, a2
 	cpu_restore_nonscratch a1
 
-	li.w		t0, _THREAD_SIZE - 32
+	li.w		t0, _THREAD_SIZE
 	PTR_ADD		t0, t0, tp
 	set_saved_sp	t0, t1, t2
 
-- 
2.31.1