[PATCH v3 2/4] riscv: consolidate ret_from_kernel_thread into ret_from_fork

From: Jisheng Zhang <jszhang@kernel.org>
To: Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>, Guo Ren <guoren@kernel.org>
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH v3 2/4] riscv: consolidate ret_from_kernel_thread into ret_from_fork
Date: Mon,  3 Oct 2022 18:29:19 +0800	[thread overview]
Message-ID: <20221003102921.3973-3-jszhang@kernel.org> (raw)
In-Reply-To: <20221003102921.3973-1-jszhang@kernel.org>

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 <jszhang@kernel.org>
Acked-by: Guo Ren <guoren@kernel.org>
---
 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 39097c1474a0..d227aca7f9d4 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)
 
 
 /*
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index 52002d54b163..fdafed185e21 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)
 {
@@ -174,7 +173,6 @@ 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 {
@@ -184,8 +182,9 @@ 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;
 }
-- 
2.37.2

