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* [PATCH v3] LoongArch: Remove unused kernel stack padding
@ 2022-10-27 11:11 Jinyang He
  2022-10-27 12:50 ` Huacai Chen
  0 siblings, 1 reply; 2+ messages in thread
From: Jinyang He @ 2022-10-27 11:11 UTC (permalink / raw)
  To: Huacai Chen, WANG Xuerui, Oleg Nesterov
  Cc: Xi Ruoyao, loongarch, linux-kernel, WANG Xuerui

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

Link: https://lore.kernel.org/loongarch/1662130897-13156-1-git-send-email-hejinyang@loongson.cn/
Reviewed-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Jinyang He <hejinyang@loongson.cn>
---
v2: Remove TOP_OF_KERNEL_STACK_PADDING
    Remove 'init stack pointer' in head.S
v3: Improve commit message suggested by Xuerui
    Add Reviewed-by tags

 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 6954dc5d24e9..7184f1dc61f2 100644
--- a/arch/loongarch/include/asm/processor.h
+++ b/arch/loongarch/include/asm/processor.h
@@ -191,7 +191,7 @@ 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 7437b9366c3b..59c4608de91d 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 97425779ce9f..84970e266658 100644
--- a/arch/loongarch/kernel/head.S
+++ b/arch/loongarch/kernel/head.S
@@ -84,10 +84,9 @@ 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
 	ASM_BUG()
diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c
index 1256e3582475..2526b68f1c0f 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
 
-- 
2.34.3


^ permalink raw reply related	[flat|nested] 2+ messages in thread
* Re: [PATCH v3] LoongArch: Remove unused kernel stack padding
  2022-10-27 11:11 [PATCH v3] LoongArch: Remove unused kernel stack padding Jinyang He
@ 2022-10-27 12:50 ` Huacai Chen
  0 siblings, 0 replies; 2+ messages in thread
From: Huacai Chen @ 2022-10-27 12:50 UTC (permalink / raw)
  To: Jinyang He
  Cc: WANG Xuerui, Oleg Nesterov, Xi Ruoyao, loongarch, linux-kernel,
	WANG Xuerui

Queued for loongarch-next, thanks.

Huacai

On Thu, Oct 27, 2022 at 7:12 PM Jinyang He <hejinyang@loongson.cn> wrote:
>
> The current LoongArch kernel stack is padded as if obeying the
> MIPS o32 calling convention, signifying the port's MIPS lineage
> but no longer making sense. Remove the padding for clarity.
>
> Link: https://lore.kernel.org/loongarch/1662130897-13156-1-git-send-email-hejinyang@loongson.cn/
> Reviewed-by: WANG Xuerui <git@xen0n.name>
> Signed-off-by: Jinyang He <hejinyang@loongson.cn>
> ---
> v2: Remove TOP_OF_KERNEL_STACK_PADDING
>     Remove 'init stack pointer' in head.S
> v3: Improve commit message suggested by Xuerui
>     Add Reviewed-by tags
>
>  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 6954dc5d24e9..7184f1dc61f2 100644
> --- a/arch/loongarch/include/asm/processor.h
> +++ b/arch/loongarch/include/asm/processor.h
> @@ -191,7 +191,7 @@ 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 7437b9366c3b..59c4608de91d 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 97425779ce9f..84970e266658 100644
> --- a/arch/loongarch/kernel/head.S
> +++ b/arch/loongarch/kernel/head.S
> @@ -84,10 +84,9 @@ 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
>         ASM_BUG()
> diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c
> index 1256e3582475..2526b68f1c0f 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
>
> --
> 2.34.3
>

^ permalink raw reply	[flat|nested] 2+ messages in thread
end of thread, other threads:[~2022-10-27 12:50 UTC | newest]

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
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2022-10-27 11:11 [PATCH v3] LoongArch: Remove unused kernel stack padding Jinyang He
2022-10-27 12:50 ` Huacai Chen

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