2022-09-28 16:41:04

by Jisheng Zhang

Subject: [PATCH v2 2/4] riscv: consolidate ret_from_kernel_thread into ret_from_fork

The ret_from_kernel_thread() behaves similarly with ret_from_fork(),
the only difference is whether call the fn(arg) or not, this can be
acchieved by testing fn is NULL or not, I.E s0 is 0 or not.

Signed-off-by: Jisheng Zhang <[email protected]>
---
arch/riscv/kernel/entry.S | 11 +++--------
arch/riscv/kernel/process.c | 5 ++---
2 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index 2207cf44a3bc..a3e1ed2fa2ac 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -323,20 +323,15 @@ END(handle_kernel_stack_overflow)

ENTRY(ret_from_fork)
call schedule_tail
- move a0, sp /* pt_regs */
- la ra, ret_from_exception
- tail syscall_exit_to_user_mode
-ENDPROC(ret_from_fork)
-
-ENTRY(ret_from_kernel_thread)
- call schedule_tail
+ beqz s0, 1f /* not from kernel thread */
/* Call fn(arg) */
move a0, s1
jalr s0
+1:
move a0, sp /* pt_regs */
la ra, ret_from_exception
tail syscall_exit_to_user_mode
-ENDPROC(ret_from_kernel_thread)
+ENDPROC(ret_from_fork)

#ifdef CONFIG_IRQ_STACKS
ENTRY(call_on_stack)
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index ceb9ebab6558..67e7cd123ceb 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -34,7 +34,6 @@ EXPORT_SYMBOL(__stack_chk_guard);
#endif

extern asmlinkage void ret_from_fork(void);
-extern asmlinkage void ret_from_kernel_thread(void);

void arch_cpu_idle(void)
{
@@ -172,7 +171,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
/* Supervisor/Machine, irqs on: */
childregs->status = SR_PP | SR_PIE;

- p->thread.ra = (unsigned long)ret_from_kernel_thread;
p->thread.s[0] = (unsigned long)args->fn;
p->thread.s[1] = (unsigned long)args->fn_arg;
} else {
@@ -182,8 +180,9 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
if (clone_flags & CLONE_SETTLS)
childregs->tp = tls;
childregs->a0 = 0; /* Return value of fork() */
- p->thread.ra = (unsigned long)ret_from_fork;
+ p->thread.s[0] = 0;
}
+ p->thread.ra = (unsigned long)ret_from_fork;
p->thread.sp = (unsigned long)childregs; /* kernel sp */
return 0;
}
--
2.34.1

2022-10-19 04:06:10

by Guo Ren

Subject: Re: [PATCH v2 2/4] riscv: consolidate ret_from_kernel_thread into ret_from_fork

I would involve this patch in the generic entry series. It would help
remove the ret_from_kernel_thread part in the entry.S.

On Thu, Sep 29, 2022 at 12:29 AM Jisheng Zhang <[email protected]> wrote:
>
> The ret_from_kernel_thread() behaves similarly with ret_from_fork(),
> the only difference is whether call the fn(arg) or not, this can be
> acchieved by testing fn is NULL or not, I.E s0 is 0 or not.
>
> Signed-off-by: Jisheng Zhang <[email protected]>
> ---
> arch/riscv/kernel/entry.S | 11 +++--------
> arch/riscv/kernel/process.c | 5 ++---
> 2 files changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> index 2207cf44a3bc..a3e1ed2fa2ac 100644
> --- a/arch/riscv/kernel/entry.S
> +++ b/arch/riscv/kernel/entry.S
> @@ -323,20 +323,15 @@ END(handle_kernel_stack_overflow)
>
> ENTRY(ret_from_fork)
> call schedule_tail
> - move a0, sp /* pt_regs */
> - la ra, ret_from_exception
> - tail syscall_exit_to_user_mode
> -ENDPROC(ret_from_fork)
> -
> -ENTRY(ret_from_kernel_thread)
> - call schedule_tail
> + beqz s0, 1f /* not from kernel thread */
> /* Call fn(arg) */
> move a0, s1
> jalr s0
> +1:
> move a0, sp /* pt_regs */
> la ra, ret_from_exception
> tail syscall_exit_to_user_mode
> -ENDPROC(ret_from_kernel_thread)
> +ENDPROC(ret_from_fork)
>
> #ifdef CONFIG_IRQ_STACKS
> ENTRY(call_on_stack)
> diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
> index ceb9ebab6558..67e7cd123ceb 100644
> --- a/arch/riscv/kernel/process.c
> +++ b/arch/riscv/kernel/process.c
> @@ -34,7 +34,6 @@ EXPORT_SYMBOL(__stack_chk_guard);
> #endif
>
> extern asmlinkage void ret_from_fork(void);
> -extern asmlinkage void ret_from_kernel_thread(void);
>
> void arch_cpu_idle(void)
> {
> @@ -172,7 +171,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
> /* Supervisor/Machine, irqs on: */
> childregs->status = SR_PP | SR_PIE;
>
> - p->thread.ra = (unsigned long)ret_from_kernel_thread;
> p->thread.s[0] = (unsigned long)args->fn;
> p->thread.s[1] = (unsigned long)args->fn_arg;
> } else {
> @@ -182,8 +180,9 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
> if (clone_flags & CLONE_SETTLS)
> childregs->tp = tls;
> childregs->a0 = 0; /* Return value of fork() */
> - p->thread.ra = (unsigned long)ret_from_fork;
> + p->thread.s[0] = 0;
> }
> + p->thread.ra = (unsigned long)ret_from_fork;
> p->thread.sp = (unsigned long)childregs; /* kernel sp */
> return 0;
> }
> --
> 2.34.1
>


--
Best Regards
Guo Ren