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From: Charlie Jenkins <charlie@rivosinc.com>
To: Paul Walmsley <paul.walmsley@sifive.com>,
	 Palmer Dabbelt <palmer@dabbelt.com>,
	Huacai Chen <chenhuacai@kernel.org>,
	 WANG Xuerui <kernel@xen0n.name>,
	Thomas Gleixner <tglx@linutronix.de>,
	 Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@kernel.org>,
	 Alexandre Ghiti <alexghiti@rivosinc.com>,
	Arnd Bergmann <arnd@arndb.de>,  Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alex@ghiti.fr>
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	 loongarch@lists.linux.dev,
	Charlie Jenkins <charlie@rivosinc.com>
Subject: [PATCH v6 3/4] LoongArch: entry: Migrate ret_from_fork() to C
Date: Thu, 20 Mar 2025 10:29:23 -0700	[thread overview]
Message-ID: <20250320-riscv_optimize_entry-v6-3-63e187e26041@rivosinc.com> (raw)
In-Reply-To: <20250320-riscv_optimize_entry-v6-0-63e187e26041@rivosinc.com>

LoongArch is the only architecture that calls
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 <charlie@rivosinc.com>
---
 arch/loongarch/include/asm/asm-prototypes.h |  8 +++++++
 arch/loongarch/kernel/entry.S               | 22 +++++++++----------
 arch/loongarch/kernel/process.c             | 33 +++++++++++++++++++++++------
 3 files changed, 45 insertions(+), 18 deletions(-)

diff --git a/arch/loongarch/include/asm/asm-prototypes.h b/arch/loongarch/include/asm/asm-prototypes.h
index 51f224bcfc654228ae423e9a066b25b35102a5b9..704066b4f7368be15be960fadbcd6c2574bbf6c0 100644
--- a/arch/loongarch/include/asm/asm-prototypes.h
+++ b/arch/loongarch/include/asm/asm-prototypes.h
@@ -12,3 +12,11 @@ __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_fork(struct task_struct *prev,
+							   struct pt_regs *regs);
+
+asmlinkage void noinstr __no_stack_protector ret_from_kernel_thread(struct task_struct *prev,
+								    struct pt_regs *regs,
+								    int (*fn)(void *),
+								    void *fn_arg);
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..98bc60d7c550fcc0225e8452f81a7d6cd7888015 100644
--- a/arch/loongarch/kernel/process.c
+++ b/arch/loongarch/kernel/process.c
@@ -14,6 +14,7 @@
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/errno.h>
+#include <linux/entry-common.h>
 #include <linux/sched.h>
 #include <linux/sched/debug.h>
 #include <linux/sched/task.h>
@@ -33,6 +34,7 @@
 #include <linux/prctl.h>
 #include <linux/nmi.h>
 
+#include <asm/asm-prototypes.h>
 #include <asm/asm.h>
 #include <asm/bootinfo.h>
 #include <asm/cpu.h>
@@ -47,6 +49,7 @@
 #include <asm/pgtable.h>
 #include <asm/processor.h>
 #include <asm/reg.h>
+#include <asm/switch_to.h>
 #include <asm/unwind.h>
 #include <asm/vdso.h>
 
@@ -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 +142,23 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 	return 0;
 }
 
+asmlinkage 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);
+}
+
+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);
+	syscall_exit_to_user_mode(regs);
+}
+
 /*
  * Copy architecture-specific thread state
  */
@@ -165,8 +186,8 @@ 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 +203,8 @@ 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


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  parent reply	other threads:[~2025-03-20 17:31 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-03-20 17:29 [PATCH v6 0/4] entry: Move ret_from_fork() to C and inline syscall_exit_to_user_mode() Charlie Jenkins
2025-03-20 17:29 ` [PATCH v6 1/4] riscv: entry: Convert ret_from_fork() to C Charlie Jenkins
2025-03-20 17:29 ` [PATCH v6 2/4] riscv: entry: Split ret_from_fork() into user and kernel Charlie Jenkins
2025-03-21  6:36   ` Alexandre Ghiti
2025-03-20 17:29 ` Charlie Jenkins [this message]
2025-05-05  4:58   ` [PATCH v6 3/4] LoongArch: entry: Migrate ret_from_fork() to C Huacai Chen
2025-03-20 17:29 ` [PATCH v6 4/4] entry: Inline syscall_exit_to_user_mode() Charlie Jenkins
2025-03-21 21:22 ` [PATCH v6 0/4] entry: Move ret_from_fork() to C and inline syscall_exit_to_user_mode() Thomas Gleixner
2025-04-28 21:54   ` Charlie Jenkins
2025-04-29  6:22     ` Thomas Gleixner

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