From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 28A414682 for ; Sun, 25 Sep 2022 23:25:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C54ADC433B5 for ; Sun, 25 Sep 2022 23:25:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1664148343; bh=0qWW3ytRn5sqjDChA6hp83Pha33NNRIB+EMSPBMJ1W4=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=QiEIB8UQYML9DR5RHuTQU83t6r3TU4wJLraulIDsfvfVsNgi/u/Ko7peUvZJrhSIo qQGeuc528E/TOFTkdFT5ftrzMAK1Apz+f9/iQQp1zY8j+p9Xr9+7Tkx4VwyoK9VyK6 sWoovwaVAIisUMA/knsbc7F9SeEabWartQrlOmmOT/1T3uVTU+MeQIvbASIIwahpv4 RVJ4UsbfHnibswZDjiXsHrHo1Smgz5IpGvS4U/3hZzj1GGqRN0u/iJ2PBHFVTgJPB9 PBP247rYS6xMKnhDIxjkDZKqVP4M/6NS4OZ7spvr1VJXT1QmICbRy5fLNegNt3jrHd S1YGjNm7YBGEQ== Received: by mail-ot1-f41.google.com with SMTP id e24-20020a05683013d800b0065be336b8feso3464383otq.8 for ; Sun, 25 Sep 2022 16:25:43 -0700 (PDT) X-Gm-Message-State: ACrzQf2KADeeIW5tMeUplr6PgV2V2SJ08ZUOhCEnNtZlVSHo8GhT1uHP WeW1wOMHq6OrZSaBfnE3VtFlh8I6h2cEOT69nmY= X-Google-Smtp-Source: AMsMyM6ks0NsA08B8/+Ccexe8yxOmM2z3hYh5K0DREm4vqGj/TSiiZYOLw8pMRmxxJcEg0vfSeV6UJvIawj0R+0XeQo= X-Received: by 2002:a05:6830:34a4:b0:65a:b03:54cc with SMTP id c36-20020a05683034a400b0065a0b0354ccmr8647715otu.140.1664148342896; Sun, 25 Sep 2022 16:25:42 -0700 (PDT) Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20220925175356.681-1-jszhang@kernel.org> <20220925175356.681-3-jszhang@kernel.org> In-Reply-To: <20220925175356.681-3-jszhang@kernel.org> From: Guo Ren Date: Mon, 26 Sep 2022 07:25:30 +0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 2/4] riscv: consolidate ret_from_kernel_thread into ret_from_fork To: Jisheng Zhang Cc: Paul Walmsley , Palmer Dabbelt , Albert Ou , Nathan Chancellor , Nick Desaulniers , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev Content-Type: text/plain; charset="UTF-8" On Mon, Sep 26, 2022 at 2:03 AM Jisheng Zhang 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 > --- > 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 */ We can't use s0 as condition for ret_from_fork/ret_from_kernel_thread. The s0=0 is also okay for ret_from_fork. /* p->thread holds context to be restored by __switch_to() */ if (unlikely(args->fn)) { /* Kernel thread */ memset(childregs, 0, sizeof(struct pt_regs)); childregs->gp = gp_in_global; /* 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 { *childregs = *(current_pt_regs()); ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ if (usp) /* User fork */ childregs->sp = usp; 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.sp = (unsigned long)childregs; /* kernel sp */ > /* 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