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

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Tested-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Guo Ren <guoren@kernel.org>
Link: https://lore.kernel.org/r/20230222033021.983168-7-guoren@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index bc322f9..5ccef25 100644 (file)
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -132,7 +132,6 @@ SYM_CODE_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)
@@ -334,20 +333,15 @@ SYM_CODE_END(handle_kernel_stack_overflow)
 
 SYM_CODE_START(ret_from_fork)
        call schedule_tail
-       move a0, sp /* pt_regs */
-       la ra, ret_from_exception
-       tail syscall_exit_to_user_mode
-SYM_CODE_END(ret_from_fork)
-
-SYM_CODE_START(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
-SYM_CODE_END(ret_from_kernel_thread)
+SYM_CODE_END(ret_from_fork)
 
 /*
  * Integer register context switch

diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index 774ffde..e2a0600 100644 (file)
--- 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)
 {
@@ -173,7 +172,6 @@ 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 {
@@ -183,8 +181,9 @@ 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;
 }