Commit 0c149401 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'core-entry-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull core entry code updates from Thomas Gleixner:
 "Updates for the generic and architecture entry code:

   - Move LoongArch and RISC-V ret_from_fork() implementations to C code
     so that syscall_exit_user_mode() can be inlined

   - Split the RISC-V ret_from_fork() implementation into return to user
     and return to kernel, which gives a measurable performance
     improvement

   - Inline syscall_exit_user_mode() which benefits all architectures by
     avoiding a function call and letting the compiler do better
     optimizations"

* tag 'core-entry-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  LoongArch: entry: Fix include order
  entry: Inline syscall_exit_to_user_mode()
  LoongArch: entry: Migrate ret_from_fork() to C
  riscv: entry: Split ret_from_fork() into user and kernel
  riscv: entry: Convert ret_from_fork() to C
parents 914873bc 8278fd60

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
@@ -13,6 +13,7 @@ 
#include <linux/cpu.h>

#include <linux/init.h>

#include <linux/kernel.h>

#include <linux/entry-common.h>

#include <linux/errno.h>

#include <linux/sched.h>

#include <linux/sched/debug.h>
@@ -34,6 +35,7 @@ 
#include <linux/nmi.h>



#include <asm/asm.h>

#include <asm/asm-prototypes.h>

#include <asm/bootinfo.h>

#include <asm/cpu.h>

#include <asm/elf.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

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

+2 −0
Original line number Diff line number Diff line
@@ -52,6 +52,8 @@ DECLARE_DO_ERROR_INFO(do_trap_ecall_s); 
DECLARE_DO_ERROR_INFO(do_trap_ecall_m);

DECLARE_DO_ERROR_INFO(do_trap_break);



asmlinkage void ret_from_fork_kernel(void *fn_arg, int (*fn)(void *), struct pt_regs *regs);

asmlinkage void ret_from_fork_user(struct pt_regs *regs);

asmlinkage void handle_bad_stack(struct pt_regs *regs);

asmlinkage void do_page_fault(struct pt_regs *regs);

asmlinkage void do_irq(struct pt_regs *regs);

arch/riscv/kernel/entry.S

+12 −8
Original line number Diff line number Diff line
@@ -319,17 +319,21 @@ SYM_CODE_END(handle_kernel_stack_overflow) 
ASM_NOKPROBE(handle_kernel_stack_overflow)

#endif



SYM_CODE_START(ret_from_fork)

SYM_CODE_START(ret_from_fork_kernel_asm)

	call schedule_tail

	move a0, s1 /* fn_arg */

	move a1, s0 /* fn */

	move a2, sp /* pt_regs */

	call ret_from_fork_kernel

	j ret_from_exception

SYM_CODE_END(ret_from_fork_kernel_asm)



SYM_CODE_START(ret_from_fork_user_asm)

	call schedule_tail

	beqz s0, 1f	/* not from kernel thread */

	/* Call fn(arg) */

	move a0, s1

	jalr s0

1:

	move a0, sp /* pt_regs */

	call syscall_exit_to_user_mode

	call ret_from_fork_user

	j ret_from_exception

SYM_CODE_END(ret_from_fork)

SYM_CODE_END(ret_from_fork_user_asm)



#ifdef CONFIG_IRQ_STACKS

/*