Commit 7ace1602 authored by Charlie Jenkins's avatar Charlie Jenkins Committed by Thomas Gleixner
Browse files

LoongArch: entry: Migrate ret_from_fork() to C 



LoongArch is the only architecture that calls syscall_exit_to_user_mode()
from assembly.

Move the call into C so that this function can be inlined across all
architectures.

Signed-off-by: default avatarCharlie Jenkins <charlie@rivosinc.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250320-riscv_optimize_entry-v6-3-63e187e26041@rivosinc.com
parent 5b3d6103

arch/loongarch/include/asm/asm-prototypes.h

+8 −0
Original line number Diff line number Diff line
@@ -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);

arch/loongarch/kernel/entry.S

+10 −12
Original line number Diff line number Diff line
@@ -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)

arch/loongarch/kernel/process.c

+27 −6
Original line number Diff line number Diff line
@@ -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