Commit 5bd2e97c authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

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: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent 36cb0e1c

arch/alpha/kernel/process.c

+3 −4
Original line number Diff line number Diff line
@@ -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;

arch/arc/kernel/process.c

+3 −4
Original line number Diff line number Diff line
@@ -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;

	}

arch/arm/kernel/process.c

+3 −4
Original line number Diff line number Diff line
@@ -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;

arch/arm64/kernel/process.c

+3 −4
Original line number Diff line number Diff line
@@ -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;

arch/csky/kernel/process.c

+3 −4
Original line number Diff line number Diff line
@@ -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());