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Fri, 24 Jan 2025 10:28:52 -0800 (PST) Date: Fri, 24 Jan 2025 10:28:50 -0800 From: Charlie Jenkins To: Huacai Chen Cc: Paul Walmsley , Palmer Dabbelt , WANG Xuerui , Thomas Gleixner , Peter Zijlstra , Andy Lutomirski , Alexandre Ghiti , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev Subject: Re: [PATCH v2 3/4] loongarch: entry: Migrate ret_from_fork() to C Message-ID: References: <20250123-riscv_optimize_entry-v2-0-7c259492d508@rivosinc.com> <20250123-riscv_optimize_entry-v2-3-7c259492d508@rivosinc.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Fri, Jan 24, 2025 at 05:05:21PM +0800, Huacai Chen wrote: > Hi, Charlie, > > On Fri, Jan 24, 2025 at 3:15 AM Charlie Jenkins wrote: > > > > Loongarch is the only architecture that calls > We usually use "LoongArch" instead of "loongarch" or "Loongarch". > > > syscall_exit_to_user_mode() from asm. Move the call into C so that this > > function can be inlined across all architectures. > > > > Signed-off-by: Charlie Jenkins > > --- > > arch/loongarch/include/asm/asm-prototypes.h | 5 +++++ > > arch/loongarch/include/asm/switch_to.h | 8 +++++++ > > arch/loongarch/kernel/entry.S | 22 +++++++++---------- > > arch/loongarch/kernel/process.c | 34 ++++++++++++++++++++++++----- > > 4 files changed, 51 insertions(+), 18 deletions(-) > > > > diff --git a/arch/loongarch/include/asm/asm-prototypes.h b/arch/loongarch/include/asm/asm-prototypes.h > > index 51f224bcfc654228ae423e9a066b25b35102a5b9..0195d4309fd29f94664d5f34247198c769033b1b 100644 > > --- a/arch/loongarch/include/asm/asm-prototypes.h > > +++ b/arch/loongarch/include/asm/asm-prototypes.h > > @@ -12,3 +12,8 @@ __int128_t __ashlti3(__int128_t a, int b); > > __int128_t __ashrti3(__int128_t a, int b); > > __int128_t __lshrti3(__int128_t a, int b); > > #endif > > + > > +asmlinkage void noinstr __no_stack_protector ret_from_kernel_thread(struct task_struct *prev, > > + struct pt_regs *regs, > > + int (*fn)(void *), > > + void *fn_arg); > It is a little strange that we only need to declare > ret_from_kernel_thread() but not ret_from_fork(). Just an oversight by me, thank you for pointing that out. > > > diff --git a/arch/loongarch/include/asm/switch_to.h b/arch/loongarch/include/asm/switch_to.h > > index 5b225aff3ba21aa06d0713bc8e73e1b941389630..a1c5576f1fd145670e13038bec6dd390486099ab 100644 > > --- a/arch/loongarch/include/asm/switch_to.h > > +++ b/arch/loongarch/include/asm/switch_to.h > > @@ -26,6 +26,14 @@ extern asmlinkage struct task_struct *__switch_to(struct task_struct *prev, > > struct task_struct *next, struct thread_info *next_ti, > > void *sched_ra, void *sched_cfa); > > > > +void noinstr __no_stack_protector ret_from_kernel_thread(struct task_struct *prev, > > + struct pt_regs *regs, > > + int (*fn)(void *), > > + void *fn_arg); > > + > > +void noinstr __no_stack_protector ret_from_fork(struct task_struct *prev, > > + struct pt_regs *regs); > > + > I prefer alpha-betical order, which means put ret_from_fork() before > ret_from_kernel_thread(). Makes sense! > > > /* > > * For newly created kernel threads switch_to() will return to > > * ret_from_kernel_thread, newly created user threads to ret_from_fork. > > diff --git a/arch/loongarch/kernel/entry.S b/arch/loongarch/kernel/entry.S > > index 48e7e34e355e83eae8165957ba2eac05a8bf17df..2abc29e573810e000f2fef4646ddca0dbb80eabe 100644 > > --- a/arch/loongarch/kernel/entry.S > > +++ b/arch/loongarch/kernel/entry.S > > @@ -77,24 +77,22 @@ SYM_CODE_START(handle_syscall) > > SYM_CODE_END(handle_syscall) > > _ASM_NOKPROBE(handle_syscall) > > > > -SYM_CODE_START(ret_from_fork) > > +SYM_CODE_START(ret_from_fork_asm) > > UNWIND_HINT_REGS > > - bl schedule_tail # a0 = struct task_struct *prev > > - move a0, sp > > - bl syscall_exit_to_user_mode > > + move a1, sp > > + bl ret_from_fork > > RESTORE_STATIC > > RESTORE_SOME > > RESTORE_SP_AND_RET > > -SYM_CODE_END(ret_from_fork) > > +SYM_CODE_END(ret_from_fork_asm) > > > > -SYM_CODE_START(ret_from_kernel_thread) > > +SYM_CODE_START(ret_from_kernel_thread_asm) > > UNWIND_HINT_REGS > > - bl schedule_tail # a0 = struct task_struct *prev > > - move a0, s1 > > - jirl ra, s0, 0 > > - move a0, sp > > - bl syscall_exit_to_user_mode > > + move a1, sp > > + move a2, s0 > > + move a3, s1 > > + bl ret_from_kernel_thread > > RESTORE_STATIC > > RESTORE_SOME > > RESTORE_SP_AND_RET > > -SYM_CODE_END(ret_from_kernel_thread) > > +SYM_CODE_END(ret_from_kernel_thread_asm) > > diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c > > index 6e58f65455c7ca3eae2e88ed852c8655a6701e5c..16cc949fe43443d70f1d865ce04595c2d8c1615b 100644 > > --- a/arch/loongarch/kernel/process.c > > +++ b/arch/loongarch/kernel/process.c > > @@ -14,6 +14,7 @@ > > #include > > #include > > #include > > +#include > > #include > > #include > > #include > > @@ -33,6 +34,7 @@ > > #include > > #include > > > > +#include > > #include > > #include > > #include > > @@ -47,6 +49,7 @@ > > #include > > #include > > #include > > +#include > > #include > > #include > > > > @@ -63,8 +66,9 @@ EXPORT_SYMBOL(__stack_chk_guard); > > unsigned long boot_option_idle_override = IDLE_NO_OVERRIDE; > > EXPORT_SYMBOL(boot_option_idle_override); > > > > -asmlinkage void ret_from_fork(void); > > -asmlinkage void ret_from_kernel_thread(void); > > +asmlinkage void restore_and_ret(void); > > +asmlinkage void ret_from_fork_asm(void); > > +asmlinkage void ret_from_kernel_thread_asm(void); > > > > void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp) > > { > > @@ -138,6 +142,24 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) > > return 0; > > } > > > > +asmlinkage void noinstr __no_stack_protector ret_from_kernel_thread(struct task_struct *prev, > > + struct pt_regs *regs, > > + int (*fn)(void *), > > + void *fn_arg) > > +{ > > + schedule_tail(prev); > > + > > + fn(fn_arg); > > + > The two blank lines can be removed, and again, I prefer alpha-betical > order, which means put ret_from_fork() before > ret_from_kernel_thread(). Will update in the next version. - Charlie > > Huacai > > > + syscall_exit_to_user_mode(regs); > > +} > > + > > +void noinstr __no_stack_protector ret_from_fork(struct task_struct *prev, struct pt_regs *regs) > > +{ > > + schedule_tail(prev); > > + syscall_exit_to_user_mode(regs); > > +} > > + > > /* > > * Copy architecture-specific thread state > > */ > > @@ -165,8 +187,8 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) > > p->thread.reg03 = childksp; > > p->thread.reg23 = (unsigned long)args->fn; > > p->thread.reg24 = (unsigned long)args->fn_arg; > > - p->thread.reg01 = (unsigned long)ret_from_kernel_thread; > > - p->thread.sched_ra = (unsigned long)ret_from_kernel_thread; > > + p->thread.reg01 = (unsigned long)ret_from_kernel_thread_asm; > > + p->thread.sched_ra = (unsigned long)ret_from_kernel_thread_asm; > > memset(childregs, 0, sizeof(struct pt_regs)); > > childregs->csr_euen = p->thread.csr_euen; > > childregs->csr_crmd = p->thread.csr_crmd; > > @@ -182,8 +204,8 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) > > childregs->regs[3] = usp; > > > > p->thread.reg03 = (unsigned long) childregs; > > - p->thread.reg01 = (unsigned long) ret_from_fork; > > - p->thread.sched_ra = (unsigned long) ret_from_fork; > > + p->thread.reg01 = (unsigned long) ret_from_fork_asm; > > + p->thread.sched_ra = (unsigned long) ret_from_fork_asm; > > > > /* > > * New tasks lose permission to use the fpu. This accelerates context > > > > -- > > 2.43.0 > >