[-next,V10,06/10] riscv: entry: Consolidate ret_from_kernel_thread into ret_from_fork

Commit Message

Guo Ren Dec. 8, 2022, 2:58 a.m. UTC

From: Jisheng Zhang <[e-mail]>

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
achieved by testing fn is NULL or not, I.E s0 is 0 or not. Many
architectures have done the same thing, it make entry.S more clean.

Signed-off-by: Jisheng Zhang <[e-mail]>
Reviewed-by: Guo Ren <[e-mail]>
Tested-by: Guo Ren <[e-mail]>
Signed-off-by: Guo Ren <[e-mail]>
---
 arch/riscv/kernel/entry.S   | 12 +++---------
 arch/riscv/kernel/process.c |  5 ++---
 2 files changed, 5 insertions(+), 12 deletions(-)

Comments

Björn Töpel Dec. 8, 2022, 10:12 a.m. UTC | #1

[e-mail] writes:

> From: Jisheng Zhang <[e-mail]>
>
> 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
> achieved by testing fn is NULL or not, I.E s0 is 0 or not. Many
> architectures have done the same thing, it make entry.S more clean.

Nit: "it makes".


Björn

Guo Ren Dec. 9, 2022, 2:01 a.m. UTC | #2

On Thu, Dec 8, 2022 at 6:12 PM Björn Töpel <[e-mail]> wrote:
>
> [e-mail] writes:
>
> > From: Jisheng Zhang <[e-mail]>
> >
> > 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
> > achieved by testing fn is NULL or not, I.E s0 is 0 or not. Many
> > architectures have done the same thing, it make entry.S more clean.
>
> Nit: "it makes".
Okay.

>
>
> Björn

Patch

diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index 69097dfffdc9..e4a9140a5b99 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -132,7 +132,6 @@  END(handle_exception)
  * caller list:
  *  - handle_exception
  *  - ret_from_fork
- *  - ret_from_kernel_thread
  */
 SYM_CODE_START_NOALIGN(ret_from_exception)
 	REG_L s0, PT_STATUS(sp)
@@ -323,20 +322,15 @@  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)
 
 
 /*
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index b0c63e8e867e..5108c76a14dd 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;
 }