From c5febea0956fd3874e8fb59c6f84d68f128d68f8 Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Fri, 8 Apr 2022 18:07:50 -0500
Subject: fork: Pass struct kernel_clone_args into copy_thread

With io_uring we have started supporting tasks that are for most
purposes user space tasks that exclusively run code in kernel mode.

The kernel task that exec's init and tasks that exec user mode
helpers are also user mode tasks that just run kernel code
until they call kernel execve.

Pass kernel_clone_args into copy_thread so these oddball
tasks can be supported more cleanly and easily.

v2: Fix spelling of kenrel_clone_args on h8300
Link: https://lkml.kernel.org/r/20220506141512.516114-2-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 arch/arc/kernel/process.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

(limited to 'arch/arc')

diff --git a/arch/arc/kernel/process.c b/arch/arc/kernel/process.c
index 5f7f5aab361f..caf948ba647c 100644
--- a/arch/arc/kernel/process.c
+++ b/arch/arc/kernel/process.c
@@ -162,10 +162,12 @@ asmlinkage void ret_from_fork(void);
  * |    user_r25    |
  * ------------------  <===== END of PAGE
  */
-int copy_thread(unsigned long clone_flags, unsigned long usp,
-		unsigned long kthread_arg, struct task_struct *p,
-		unsigned long tls)
+int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
+	unsigned long clone_flags = args->flags;
+	unsigned long usp = args->stack;
+	unsigned long kthread_arg = args->stack_size;
+	unsigned long tls = args->tls;
 	struct pt_regs *c_regs;        /* child's pt_regs */
 	unsigned long *childksp;       /* to unwind out of __switch_to() */
 	struct callee_regs *c_callee;  /* child's callee regs */
-- 
cgit v1.2.3


From 5bd2e97c868a8a44470950ed01846cab6328e540 Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Tue, 12 Apr 2022 10:18:48 -0500
Subject: fork: Generalize PF_IO_WORKER handling

Add fn and fn_arg members into struct kernel_clone_args and test for
them in copy_thread (instead of testing for PF_KTHREAD | PF_IO_WORKER).
This allows any task that wants to be a user space task that only runs
in kernel mode to use this functionality.

The code on x86 is an exception and still retains a PF_KTHREAD test
because x86 unlikely everything else handles kthreads slightly
differently than user space tasks that start with a function.

The functions that created tasks that start with a function
have been updated to set ".fn" and ".fn_arg" instead of
".stack" and ".stack_size".  These functions are fork_idle(),
create_io_thread(), kernel_thread(), and user_mode_thread().

Link: https://lkml.kernel.org/r/20220506141512.516114-4-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 arch/alpha/kernel/process.c      |  7 +++----
 arch/arc/kernel/process.c        |  7 +++----
 arch/arm/kernel/process.c        |  7 +++----
 arch/arm64/kernel/process.c      |  7 +++----
 arch/csky/kernel/process.c       |  7 +++----
 arch/h8300/kernel/process.c      |  7 +++----
 arch/hexagon/kernel/process.c    |  7 +++----
 arch/ia64/kernel/process.c       |  6 +++---
 arch/m68k/kernel/process.c       |  7 +++----
 arch/microblaze/kernel/process.c |  7 +++----
 arch/mips/kernel/process.c       |  7 +++----
 arch/nios2/kernel/process.c      |  7 +++----
 arch/openrisc/kernel/process.c   |  7 +++----
 arch/parisc/kernel/process.c     | 11 +++++------
 arch/powerpc/kernel/process.c    |  9 ++++-----
 arch/riscv/kernel/process.c      |  7 +++----
 arch/s390/kernel/process.c       |  7 +++----
 arch/sh/kernel/process_32.c      |  7 +++----
 arch/sparc/kernel/process_32.c   |  7 +++----
 arch/sparc/kernel/process_64.c   |  7 +++----
 arch/um/kernel/process.c         | 10 ++++------
 arch/x86/include/asm/fpu/sched.h |  2 +-
 arch/x86/include/asm/switch_to.h |  8 ++++----
 arch/x86/kernel/fpu/core.c       |  4 ++--
 arch/x86/kernel/process.c        | 13 ++++++-------
 arch/xtensa/kernel/process.c     | 11 +++++------
 include/linux/sched/task.h       |  2 ++
 kernel/fork.c                    | 16 ++++++++--------
 28 files changed, 95 insertions(+), 116 deletions(-)

(limited to 'arch/arc')

diff --git a/arch/alpha/kernel/process.c b/arch/alpha/kernel/process.c
index 732e39217c7f..6cbba7370b4e 100644
--- a/arch/alpha/kernel/process.c
+++ b/arch/alpha/kernel/process.c
@@ -237,7 +237,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long usp = args->stack;
-	unsigned long kthread_arg = args->stack_size;
 	unsigned long tls = args->tls;
 	extern void ret_from_fork(void);
 	extern void ret_from_kernel_thread(void);
@@ -251,13 +250,13 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	childti->pcb.ksp = (unsigned long) childstack;
 	childti->pcb.flags = 1;	/* set FEN, clear everything else */
 
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		/* kernel thread */
 		memset(childstack, 0,
 			sizeof(struct switch_stack) + sizeof(struct pt_regs));
 		childstack->r26 = (unsigned long) ret_from_kernel_thread;
-		childstack->r9 = usp;	/* function */
-		childstack->r10 = kthread_arg;
+		childstack->r9 = (unsigned long) args->fn;
+		childstack->r10 = (unsigned long) args->fn_arg;
 		childregs->hae = alpha_mv.hae_cache;
 		childti->pcb.usp = 0;
 		return 0;
diff --git a/arch/arc/kernel/process.c b/arch/arc/kernel/process.c
index caf948ba647c..3369f0700702 100644
--- a/arch/arc/kernel/process.c
+++ b/arch/arc/kernel/process.c
@@ -166,7 +166,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long usp = args->stack;
-	unsigned long kthread_arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct pt_regs *c_regs;        /* child's pt_regs */
 	unsigned long *childksp;       /* to unwind out of __switch_to() */
@@ -193,11 +192,11 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	childksp[0] = 0;			/* fp */
 	childksp[1] = (unsigned long)ret_from_fork; /* blink */
 
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		memset(c_regs, 0, sizeof(struct pt_regs));
 
-		c_callee->r13 = kthread_arg;
-		c_callee->r14 = usp;  /* function */
+		c_callee->r13 = (unsigned long)args->fn_arg;
+		c_callee->r14 = (unsigned long)args->fn;
 
 		return 0;
 	}
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 8e13b426dd26..3d9cace63884 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -242,7 +242,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long stack_start = args->stack;
-	unsigned long stk_sz = args->stack_size;
 	unsigned long tls = args->tls;
 	struct thread_info *thread = task_thread_info(p);
 	struct pt_regs *childregs = task_pt_regs(p);
@@ -259,15 +258,15 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	thread->cpu_domain = get_domain();
 #endif
 
-	if (likely(!(p->flags & (PF_KTHREAD | PF_IO_WORKER)))) {
+	if (likely(!args->fn)) {
 		*childregs = *current_pt_regs();
 		childregs->ARM_r0 = 0;
 		if (stack_start)
 			childregs->ARM_sp = stack_start;
 	} else {
 		memset(childregs, 0, sizeof(struct pt_regs));
-		thread->cpu_context.r4 = stk_sz;
-		thread->cpu_context.r5 = stack_start;
+		thread->cpu_context.r4 = (unsigned long)args->fn_arg;
+		thread->cpu_context.r5 = (unsigned long)args->fn;
 		childregs->ARM_cpsr = SVC_MODE;
 	}
 	thread->cpu_context.pc = (unsigned long)ret_from_fork;
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index e002f6681c8d..d0ef05c661b0 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -320,7 +320,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long stack_start = args->stack;
-	unsigned long stk_sz = args->stack_size;
 	unsigned long tls = args->tls;
 	struct pt_regs *childregs = task_pt_regs(p);
 
@@ -337,7 +336,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 
 	ptrauth_thread_init_kernel(p);
 
-	if (likely(!(p->flags & (PF_KTHREAD | PF_IO_WORKER)))) {
+	if (likely(!args->fn)) {
 		*childregs = *current_pt_regs();
 		childregs->regs[0] = 0;
 
@@ -371,8 +370,8 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 		memset(childregs, 0, sizeof(struct pt_regs));
 		childregs->pstate = PSR_MODE_EL1h | PSR_IL_BIT;
 
-		p->thread.cpu_context.x19 = stack_start;
-		p->thread.cpu_context.x20 = stk_sz;
+		p->thread.cpu_context.x19 = (unsigned long)args->fn;
+		p->thread.cpu_context.x20 = (unsigned long)args->fn_arg;
 	}
 	p->thread.cpu_context.pc = (unsigned long)ret_from_fork;
 	p->thread.cpu_context.sp = (unsigned long)childregs;
diff --git a/arch/csky/kernel/process.c b/arch/csky/kernel/process.c
index 7dba33d37e1a..9af49aea1c3b 100644
--- a/arch/csky/kernel/process.c
+++ b/arch/csky/kernel/process.c
@@ -34,7 +34,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long usp = args->stack;
-	unsigned long kthread_arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct switch_stack *childstack;
 	struct pt_regs *childregs = task_pt_regs(p);
@@ -49,11 +48,11 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	/* setup thread.sp for switch_to !!! */
 	p->thread.sp = (unsigned long)childstack;
 
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		memset(childregs, 0, sizeof(struct pt_regs));
 		childstack->r15 = (unsigned long) ret_from_kernel_thread;
-		childstack->r10 = kthread_arg;
-		childstack->r9 = usp;
+		childstack->r10 = (unsigned long) args->fn_arg;
+		childstack->r9 = (unsigned long) args->fn;
 		childregs->sr = mfcr("psr");
 	} else {
 		*childregs = *(current_pt_regs());
diff --git a/arch/h8300/kernel/process.c b/arch/h8300/kernel/process.c
index 752cbd9b0bf6..9028262c96a9 100644
--- a/arch/h8300/kernel/process.c
+++ b/arch/h8300/kernel/process.c
@@ -108,16 +108,15 @@ void flush_thread(void)
 int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long usp = args->stack;
-	unsigned long topstk = args->stack_size;
 	struct pt_regs *childregs;
 
 	childregs = (struct pt_regs *) (THREAD_SIZE + task_stack_page(p)) - 1;
 
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		memset(childregs, 0, sizeof(struct pt_regs));
 		childregs->retpc = (unsigned long) ret_from_kernel_thread;
-		childregs->er4 = topstk; /* arg */
-		childregs->er5 = usp; /* fn */
+		childregs->er4 = (unsigned long) args->fn_arg;
+		childregs->er5 = (unsigned long) args->fn;
 	}  else {
 		*childregs = *current_pt_regs();
 		childregs->er0 = 0;
diff --git a/arch/hexagon/kernel/process.c b/arch/hexagon/kernel/process.c
index f1c1f6f21941..f0552f98a7ba 100644
--- a/arch/hexagon/kernel/process.c
+++ b/arch/hexagon/kernel/process.c
@@ -54,7 +54,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long usp = args->stack;
-	unsigned long arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct thread_info *ti = task_thread_info(p);
 	struct hexagon_switch_stack *ss;
@@ -76,11 +75,11 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 						    sizeof(*ss));
 	ss->lr = (unsigned long)ret_from_fork;
 	p->thread.switch_sp = ss;
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		memset(childregs, 0, sizeof(struct pt_regs));
 		/* r24 <- fn, r25 <- arg */
-		ss->r24 = usp;
-		ss->r25 = arg;
+		ss->r24 = (unsigned long)args->fn;
+		ss->r25 = (unsigned long)args->fn_arg;
 		pt_set_kmode(childregs);
 		return 0;
 	}
diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c
index 8f010ae818bc..167b1765bea1 100644
--- a/arch/ia64/kernel/process.c
+++ b/arch/ia64/kernel/process.c
@@ -341,14 +341,14 @@ copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 
 	ia64_drop_fpu(p);	/* don't pick up stale state from a CPU's fph */
 
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		if (unlikely(args->idle)) {
 			/* fork_idle() called us */
 			return 0;
 		}
 		memset(child_stack, 0, sizeof(*child_ptregs) + sizeof(*child_stack));
-		child_stack->r4 = user_stack_base;	/* payload */
-		child_stack->r5 = user_stack_size;	/* argument */
+		child_stack->r4 = (unsigned long) args->fn;
+		child_stack->r5 = (unsigned long) args->fn_arg;
 		/*
 		 * Preserve PSR bits, except for bits 32-34 and 37-45,
 		 * which we can't read.
diff --git a/arch/m68k/kernel/process.c b/arch/m68k/kernel/process.c
index 8ac575656fc4..221feb0269f1 100644
--- a/arch/m68k/kernel/process.c
+++ b/arch/m68k/kernel/process.c
@@ -142,7 +142,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long usp = args->stack;
-	unsigned long arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct fork_frame {
 		struct switch_stack sw;
@@ -160,12 +159,12 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	 */
 	p->thread.fc = USER_DATA;
 
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		/* kernel thread */
 		memset(frame, 0, sizeof(struct fork_frame));
 		frame->regs.sr = PS_S;
-		frame->sw.a3 = usp; /* function */
-		frame->sw.d7 = arg;
+		frame->sw.a3 = (unsigned long)args->fn;
+		frame->sw.d7 = (unsigned long)args->fn_arg;
 		frame->sw.retpc = (unsigned long)ret_from_kernel_thread;
 		p->thread.usp = 0;
 		return 0;
diff --git a/arch/microblaze/kernel/process.c b/arch/microblaze/kernel/process.c
index b5f549125c6a..3c6241bcaea8 100644
--- a/arch/microblaze/kernel/process.c
+++ b/arch/microblaze/kernel/process.c
@@ -56,19 +56,18 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long usp = args->stack;
-	unsigned long arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct pt_regs *childregs = task_pt_regs(p);
 	struct thread_info *ti = task_thread_info(p);
 
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		/* if we're creating a new kernel thread then just zeroing all
 		 * the registers. That's OK for a brand new thread.*/
 		memset(childregs, 0, sizeof(struct pt_regs));
 		memset(&ti->cpu_context, 0, sizeof(struct cpu_context));
 		ti->cpu_context.r1  = (unsigned long)childregs;
-		ti->cpu_context.r20 = (unsigned long)usp; /* fn */
-		ti->cpu_context.r19 = (unsigned long)arg;
+		ti->cpu_context.r20 = (unsigned long)args->fn;
+		ti->cpu_context.r19 = (unsigned long)args->fn_arg;
 		childregs->pt_mode = 1;
 		local_save_flags(childregs->msr);
 		ti->cpu_context.msr = childregs->msr & ~MSR_IE;
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index a572d097b16b..35b912bce429 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -109,7 +109,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long usp = args->stack;
-	unsigned long kthread_arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct thread_info *ti = task_thread_info(p);
 	struct pt_regs *childregs, *regs = current_pt_regs();
@@ -122,12 +121,12 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	/*  Put the stack after the struct pt_regs.  */
 	childksp = (unsigned long) childregs;
 	p->thread.cp0_status = (read_c0_status() & ~(ST0_CU2|ST0_CU1)) | ST0_KERNEL_CUMASK;
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		/* kernel thread */
 		unsigned long status = p->thread.cp0_status;
 		memset(childregs, 0, sizeof(struct pt_regs));
-		p->thread.reg16 = usp; /* fn */
-		p->thread.reg17 = kthread_arg;
+		p->thread.reg16 = (unsigned long)args->fn;
+		p->thread.reg17 = (unsigned long)args->fn_arg;
 		p->thread.reg29 = childksp;
 		p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
 #if defined(CONFIG_CPU_R3000)
diff --git a/arch/nios2/kernel/process.c b/arch/nios2/kernel/process.c
index 98c4bfe972e0..29593b98567d 100644
--- a/arch/nios2/kernel/process.c
+++ b/arch/nios2/kernel/process.c
@@ -104,7 +104,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long usp = args->stack;
-	unsigned long arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct pt_regs *childregs = task_pt_regs(p);
 	struct pt_regs *regs;
@@ -112,12 +111,12 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	struct switch_stack *childstack =
 		((struct switch_stack *)childregs) - 1;
 
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		memset(childstack, 0,
 			sizeof(struct switch_stack) + sizeof(struct pt_regs));
 
-		childstack->r16 = usp;		/* fn */
-		childstack->r17 = arg;
+		childstack->r16 = (unsigned long) args->fn;
+		childstack->r17 = (unsigned long) args->fn_arg;
 		childstack->ra = (unsigned long) ret_from_kernel_thread;
 		childregs->estatus = STATUS_PIE;
 		childregs->sp = (unsigned long) childstack;
diff --git a/arch/openrisc/kernel/process.c b/arch/openrisc/kernel/process.c
index 486e46dd5883..d9697cc9bc4d 100644
--- a/arch/openrisc/kernel/process.c
+++ b/arch/openrisc/kernel/process.c
@@ -156,7 +156,6 @@ copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long usp = args->stack;
-	unsigned long arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct pt_regs *userregs;
 	struct pt_regs *kregs;
@@ -175,10 +174,10 @@ copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	sp -= sizeof(struct pt_regs);
 	kregs = (struct pt_regs *)sp;
 
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		memset(kregs, 0, sizeof(struct pt_regs));
-		kregs->gpr[20] = usp; /* fn, kernel thread */
-		kregs->gpr[22] = arg;
+		kregs->gpr[20] = (unsigned long)args->fn;
+		kregs->gpr[22] = (unsigned long)args->fn_arg;
 	} else {
 		*userregs = *current_pt_regs();
 
diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
index 30a5874ca845..a6a2a558fc5b 100644
--- a/arch/parisc/kernel/process.c
+++ b/arch/parisc/kernel/process.c
@@ -210,7 +210,6 @@ copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long usp = args->stack;
-	unsigned long kthread_arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct pt_regs *cregs = &(p->thread.regs);
 	void *stack = task_stack_page(p);
@@ -221,7 +220,7 @@ copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	extern void * const ret_from_kernel_thread;
 	extern void * const child_return;
 
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		/* kernel thread */
 		memset(cregs, 0, sizeof(struct pt_regs));
 		if (args->idle) /* idle thread */
@@ -236,12 +235,12 @@ copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 		 * ret_from_kernel_thread.
 		 */
 #ifdef CONFIG_64BIT
-		cregs->gr[27] = ((unsigned long *)usp)[3];
-		cregs->gr[26] = ((unsigned long *)usp)[2];
+		cregs->gr[27] = ((unsigned long *)args->fn)[3];
+		cregs->gr[26] = ((unsigned long *)args->fn)[2];
 #else
-		cregs->gr[26] = usp;
+		cregs->gr[26] = (unsigned long) args->fn;
 #endif
-		cregs->gr[25] = kthread_arg;
+		cregs->gr[25] = (unsigned long) args->fn_arg;
 	} else {
 		/* user thread */
 		/* usp must be word aligned.  This also prevents users from
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 3fd67c861d54..4f367bb68906 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1720,7 +1720,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long usp = args->stack;
-	unsigned long kthread_arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct pt_regs *childregs, *kregs;
 	extern void ret_from_fork(void);
@@ -1738,18 +1737,18 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	/* Copy registers */
 	sp -= sizeof(struct pt_regs);
 	childregs = (struct pt_regs *) sp;
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		/* kernel thread */
 		memset(childregs, 0, sizeof(struct pt_regs));
 		childregs->gpr[1] = sp + sizeof(struct pt_regs);
 		/* function */
-		if (usp)
-			childregs->gpr[14] = ppc_function_entry((void *)usp);
+		if (args->fn)
+			childregs->gpr[14] = ppc_function_entry((void *)args->fn);
 #ifdef CONFIG_PPC64
 		clear_tsk_thread_flag(p, TIF_32BIT);
 		childregs->softe = IRQS_ENABLED;
 #endif
-		childregs->gpr[15] = kthread_arg;
+		childregs->gpr[15] = (unsigned long)args->fn_arg;
 		p->thread.regs = NULL;	/* no user register state */
 		ti->flags |= _TIF_RESTOREALL;
 		f = ret_from_kernel_thread;
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index 334382731725..24efabdbc551 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -124,12 +124,11 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long usp = args->stack;
-	unsigned long arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct pt_regs *childregs = task_pt_regs(p);
 
 	/* p->thread holds context to be restored by __switch_to() */
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		/* Kernel thread */
 		memset(childregs, 0, sizeof(struct pt_regs));
 		childregs->gp = gp_in_global;
@@ -137,8 +136,8 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 		childregs->status = SR_PP | SR_PIE;
 
 		p->thread.ra = (unsigned long)ret_from_kernel_thread;
-		p->thread.s[0] = usp; /* fn */
-		p->thread.s[1] = arg;
+		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 */
diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index bb5daec39516..89949b9f3cf8 100644
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -98,7 +98,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long new_stackp = args->stack;
-	unsigned long arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct fake_frame
 	{
@@ -133,15 +132,15 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	frame->sf.gprs[9] = (unsigned long)frame;
 
 	/* Store access registers to kernel stack of new process. */
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		/* kernel thread */
 		memset(&frame->childregs, 0, sizeof(struct pt_regs));
 		frame->childregs.psw.mask = PSW_KERNEL_BITS | PSW_MASK_DAT |
 				PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK;
 		frame->childregs.psw.addr =
 				(unsigned long)__ret_from_fork;
-		frame->childregs.gprs[9] = new_stackp; /* function */
-		frame->childregs.gprs[10] = arg;
+		frame->childregs.gprs[9] = (unsigned long)args->fn;
+		frame->childregs.gprs[10] = (unsigned long)args->fn_arg;
 		frame->childregs.orig_gpr2 = -1;
 		frame->childregs.last_break = 1;
 		return 0;
diff --git a/arch/sh/kernel/process_32.c b/arch/sh/kernel/process_32.c
index 6023399b1892..a808843375e7 100644
--- a/arch/sh/kernel/process_32.c
+++ b/arch/sh/kernel/process_32.c
@@ -96,7 +96,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long usp = args->stack;
-	unsigned long arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct thread_info *ti = task_thread_info(p);
 	struct pt_regs *childregs;
@@ -117,11 +116,11 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 
 	childregs = task_pt_regs(p);
 	p->thread.sp = (unsigned long) childregs;
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		memset(childregs, 0, sizeof(struct pt_regs));
 		p->thread.pc = (unsigned long) ret_from_kernel_thread;
-		childregs->regs[4] = arg;
-		childregs->regs[5] = usp;
+		childregs->regs[4] = (unsigned long) args->fn_arg;
+		childregs->regs[5] = (unsigned long) args->fn;
 		childregs->sr = SR_MD;
 #if defined(CONFIG_SH_FPU)
 		childregs->sr |= SR_FD;
diff --git a/arch/sparc/kernel/process_32.c b/arch/sparc/kernel/process_32.c
index 80e6775e18c0..33b0215a4182 100644
--- a/arch/sparc/kernel/process_32.c
+++ b/arch/sparc/kernel/process_32.c
@@ -263,7 +263,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long sp = args->stack;
-	unsigned long arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct thread_info *ti = task_thread_info(p);
 	struct pt_regs *childregs, *regs = current_pt_regs();
@@ -299,13 +298,13 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	ti->ksp = (unsigned long) new_stack;
 	p->thread.kregs = childregs;
 
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		extern int nwindows;
 		unsigned long psr;
 		memset(new_stack, 0, STACKFRAME_SZ + TRACEREG_SZ);
 		ti->kpc = (((unsigned long) ret_from_kernel_thread) - 0x8);
-		childregs->u_regs[UREG_G1] = sp; /* function */
-		childregs->u_regs[UREG_G2] = arg;
+		childregs->u_regs[UREG_G1] = (unsigned long) args->fn;
+		childregs->u_regs[UREG_G2] = (unsigned long) args->fn_arg;
 		psr = childregs->psr = get_psr();
 		ti->kpsr = psr | PSR_PIL;
 		ti->kwim = 1 << (((psr & PSR_CWP) + 1) % nwindows);
diff --git a/arch/sparc/kernel/process_64.c b/arch/sparc/kernel/process_64.c
index 38c46ca826d9..6335b698a4b4 100644
--- a/arch/sparc/kernel/process_64.c
+++ b/arch/sparc/kernel/process_64.c
@@ -568,7 +568,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long sp = args->stack;
-	unsigned long arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct thread_info *t = task_thread_info(p);
 	struct pt_regs *regs = current_pt_regs();
@@ -587,12 +586,12 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 				       sizeof(struct sparc_stackf));
 	t->fpsaved[0] = 0;
 
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(args->fn)) {
 		memset(child_trap_frame, 0, child_stack_sz);
 		__thread_flag_byte_ptr(t)[TI_FLAG_BYTE_CWP] = 
 			(current_pt_regs()->tstate + 1) & TSTATE_CWP;
-		t->kregs->u_regs[UREG_G1] = sp; /* function */
-		t->kregs->u_regs[UREG_G2] = arg;
+		t->kregs->u_regs[UREG_G1] = (unsigned long) args->fn;
+		t->kregs->u_regs[UREG_G2] = (unsigned long) args->fn_arg;
 		return 0;
 	}
 
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index fd2d2361484d..181cc9aafb25 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -158,15 +158,13 @@ int copy_thread(struct task_struct * p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long sp = args->stack;
-	unsigned long arg = args->stack_size;
 	unsigned long tls = args->tls;
 	void (*handler)(void);
-	int kthread = current->flags & (PF_KTHREAD | PF_IO_WORKER);
 	int ret = 0;
 
 	p->thread = (struct thread_struct) INIT_THREAD;
 
-	if (!kthread) {
+	if (!args->fn) {
 	  	memcpy(&p->thread.regs.regs, current_pt_regs(),
 		       sizeof(p->thread.regs.regs));
 		PT_REGS_SET_SYSCALL_RETURN(&p->thread.regs, 0);
@@ -178,14 +176,14 @@ int copy_thread(struct task_struct * p, const struct kernel_clone_args *args)
 		arch_copy_thread(&current->thread.arch, &p->thread.arch);
 	} else {
 		get_safe_registers(p->thread.regs.regs.gp, p->thread.regs.regs.fp);
-		p->thread.request.u.thread.proc = (int (*)(void *))sp;
-		p->thread.request.u.thread.arg = (void *)arg;
+		p->thread.request.u.thread.proc = args->fn;
+		p->thread.request.u.thread.arg = args->fn_arg;
 		handler = new_thread_handler;
 	}
 
 	new_thread(task_stack_page(p), &p->thread.switch_buf, handler);
 
-	if (!kthread) {
+	if (!args->fn) {
 		clear_flushed_tls(p);
 
 		/*
diff --git a/arch/x86/include/asm/fpu/sched.h b/arch/x86/include/asm/fpu/sched.h
index 99a8820e8cc4..b2486b2cbc6e 100644
--- a/arch/x86/include/asm/fpu/sched.h
+++ b/arch/x86/include/asm/fpu/sched.h
@@ -11,7 +11,7 @@
 
 extern void save_fpregs_to_fpstate(struct fpu *fpu);
 extern void fpu__drop(struct fpu *fpu);
-extern int  fpu_clone(struct task_struct *dst, unsigned long clone_flags);
+extern int  fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal);
 extern void fpu_flush_thread(void);
 
 /*
diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h
index b5f0d2ff47e4..c08eb0fdd11f 100644
--- a/arch/x86/include/asm/switch_to.h
+++ b/arch/x86/include/asm/switch_to.h
@@ -78,13 +78,13 @@ static inline void update_task_stack(struct task_struct *task)
 }
 
 static inline void kthread_frame_init(struct inactive_task_frame *frame,
-				      unsigned long fun, unsigned long arg)
+				      int (*fun)(void *), void *arg)
 {
-	frame->bx = fun;
+	frame->bx = (unsigned long)fun;
 #ifdef CONFIG_X86_32
-	frame->di = arg;
+	frame->di = (unsigned long)arg;
 #else
-	frame->r12 = arg;
+	frame->r12 = (unsigned long)arg;
 #endif
 }
 
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index c049561f373a..fbade5a3975b 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -556,7 +556,7 @@ static inline void fpu_inherit_perms(struct fpu *dst_fpu)
 }
 
 /* Clone current's FPU state on fork */
-int fpu_clone(struct task_struct *dst, unsigned long clone_flags)
+int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal)
 {
 	struct fpu *src_fpu = &current->thread.fpu;
 	struct fpu *dst_fpu = &dst->thread.fpu;
@@ -579,7 +579,7 @@ int fpu_clone(struct task_struct *dst, unsigned long clone_flags)
 	 * No FPU state inheritance for kernel threads and IO
 	 * worker threads.
 	 */
-	if (dst->flags & (PF_KTHREAD | PF_IO_WORKER)) {
+	if (minimal) {
 		/* Clear out the minimal state */
 		memcpy(&dst_fpu->fpstate->regs, &init_fpstate.regs,
 		       init_fpstate_copy_size());
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 0fce52b10dc4..d20eaad52a85 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -134,7 +134,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long sp = args->stack;
-	unsigned long arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct inactive_task_frame *frame;
 	struct fork_frame *fork_frame;
@@ -172,13 +171,13 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	frame->flags = X86_EFLAGS_FIXED;
 #endif
 
-	fpu_clone(p, clone_flags);
+	fpu_clone(p, clone_flags, args->fn);
 
 	/* Kernel thread ? */
 	if (unlikely(p->flags & PF_KTHREAD)) {
 		p->thread.pkru = pkru_get_init_value();
 		memset(childregs, 0, sizeof(struct pt_regs));
-		kthread_frame_init(frame, sp, arg);
+		kthread_frame_init(frame, args->fn, args->fn_arg);
 		return 0;
 	}
 
@@ -198,10 +197,10 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	task_user_gs(p) = get_user_gs(current_pt_regs());
 #endif
 
-	if (unlikely(p->flags & PF_IO_WORKER)) {
+	if (unlikely(args->fn)) {
 		/*
-		 * An IO thread is a user space thread, but it doesn't
-		 * return to ret_after_fork().
+		 * A user space thread, but it doesn't return to
+		 * ret_after_fork().
 		 *
 		 * In order to indicate that to tools like gdb,
 		 * we reset the stack and instruction pointers.
@@ -211,7 +210,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 		 */
 		childregs->sp = 0;
 		childregs->ip = 0;
-		kthread_frame_init(frame, sp, arg);
+		kthread_frame_init(frame, args->fn, args->fn_arg);
 		return 0;
 	}
 
diff --git a/arch/xtensa/kernel/process.c b/arch/xtensa/kernel/process.c
index 15ce25073142..c3751cc88e5d 100644
--- a/arch/xtensa/kernel/process.c
+++ b/arch/xtensa/kernel/process.c
@@ -205,7 +205,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 {
 	unsigned long clone_flags = args->flags;
 	unsigned long usp_thread_fn = args->stack;
-	unsigned long thread_fn_arg = args->stack_size;
 	unsigned long tls = args->tls;
 	struct pt_regs *childregs = task_pt_regs(p);
 
@@ -226,7 +225,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 #error Unsupported Xtensa ABI
 #endif
 
-	if (!(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (!args->fn) {
 		struct pt_regs *regs = current_pt_regs();
 		unsigned long usp = usp_thread_fn ?
 			usp_thread_fn : regs->areg[1];
@@ -278,15 +277,15 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 		 * Window underflow will load registers from the
 		 * spill slots on the stack on return from _switch_to.
 		 */
-		SPILL_SLOT(childregs, 2) = usp_thread_fn;
-		SPILL_SLOT(childregs, 3) = thread_fn_arg;
+		SPILL_SLOT(childregs, 2) = (unsigned long)args->fn;
+		SPILL_SLOT(childregs, 3) = (unsigned long)args->fn_arg;
 #elif defined(__XTENSA_CALL0_ABI__)
 		/*
 		 * a12 = thread_fn, a13 = thread_fn arg.
 		 * _switch_to epilogue will load registers from the stack.
 		 */
-		((unsigned long *)p->thread.sp)[0] = usp_thread_fn;
-		((unsigned long *)p->thread.sp)[1] = thread_fn_arg;
+		((unsigned long *)p->thread.sp)[0] = (unsigned long)args->fn;
+		((unsigned long *)p->thread.sp)[1] = (unsigned long)args->fn_arg;
 #else
 #error Unsupported Xtensa ABI
 #endif
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 3d6b99ce5408..505aaf9fe477 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -34,6 +34,8 @@ struct kernel_clone_args {
 	int io_thread;
 	int kthread;
 	int idle;
+	int (*fn)(void *);
+	void *fn_arg;
 	struct cgroup *cgrp;
 	struct css_set *cset;
 };
diff --git a/kernel/fork.c b/kernel/fork.c
index 93d77ee921ff..8e17c3fbce42 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2555,8 +2555,8 @@ struct task_struct * __init fork_idle(int cpu)
 	struct task_struct *task;
 	struct kernel_clone_args args = {
 		.flags		= CLONE_VM,
-		.stack		= (unsigned long)&idle_dummy,
-		.stack_size	= (unsigned long)NULL,
+		.fn		= &idle_dummy,
+		.fn_arg		= NULL,
 		.kthread	= 1,
 		.idle		= 1,
 	};
@@ -2589,8 +2589,8 @@ struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
 		.flags		= ((lower_32_bits(flags) | CLONE_VM |
 				    CLONE_UNTRACED) & ~CSIGNAL),
 		.exit_signal	= (lower_32_bits(flags) & CSIGNAL),
-		.stack		= (unsigned long)fn,
-		.stack_size	= (unsigned long)arg,
+		.fn		= fn,
+		.fn_arg		= arg,
 		.io_thread	= 1,
 	};
 
@@ -2694,8 +2694,8 @@ pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
 		.flags		= ((lower_32_bits(flags) | CLONE_VM |
 				    CLONE_UNTRACED) & ~CSIGNAL),
 		.exit_signal	= (lower_32_bits(flags) & CSIGNAL),
-		.stack		= (unsigned long)fn,
-		.stack_size	= (unsigned long)arg,
+		.fn		= fn,
+		.fn_arg		= arg,
 		.kthread	= 1,
 	};
 
@@ -2711,8 +2711,8 @@ pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags)
 		.flags		= ((lower_32_bits(flags) | CLONE_VM |
 				    CLONE_UNTRACED) & ~CSIGNAL),
 		.exit_signal	= (lower_32_bits(flags) & CSIGNAL),
-		.stack		= (unsigned long)fn,
-		.stack_size	= (unsigned long)arg,
+		.fn		= fn,
+		.fn_arg		= arg,
 	};
 
 	return kernel_clone(&args);
-- 
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