sparc64: switch to generic kernel_thread()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/sparc/Kconfig

@@ -74,6 +74,7 @@ config SPARC64
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select HAVE_C_RECORDMCOUNT
 	select NO_BOOTMEM
+	select GENERIC_KERNEL_THREAD
 
 config ARCH_DEFCONFIG
 	string

arch/sparc/include/asm/processor_64.h

@@ -188,8 +188,6 @@ do { \
 /* Free all resources held by a thread. */
 #define release_thread(tsk)		do { } while (0)
 
-extern pid_t kernel_thread(int (*fn)(void *), void * arg, unsigned long flags);
-
 extern unsigned long get_wchan(struct task_struct *task);
 
 #define task_pt_regs(tsk) (task_thread_info(tsk)->kregs)

arch/sparc/include/asm/ptrace.h

@@ -32,6 +32,9 @@ static inline bool pt_regs_clear_syscall(struct pt_regs *regs)
 #define arch_ptrace_stop(exit_code, info) \
 	synchronize_user_stack()
 
+#define current_pt_regs() \
+	((struct pt_regs *)((unsigned long)current_thread_info() + THREAD_SIZE) - 1)
+
 struct global_reg_snapshot {
 	unsigned long		tstate;
 	unsigned long		tpc;

arch/sparc/kernel/process_64.c

@@ -538,64 +538,56 @@ asmlinkage long sparc_do_fork(unsigned long clone_flags,
  * Child  -->  %o0 == parents pid, %o1 == 1
  */
 int copy_thread(unsigned long clone_flags, unsigned long sp,
-		unsigned long unused,
+		unsigned long arg,
 		struct task_struct *p, struct pt_regs *regs)
 {
 	struct thread_info *t = task_thread_info(p);
 	struct sparc_stackf *parent_sf;
 	unsigned long child_stack_sz;
 	char *child_trap_frame;
-	int kernel_thread;
-
-	kernel_thread = (regs->tstate & TSTATE_PRIV) ? 1 : 0;
-	parent_sf = ((struct sparc_stackf *) regs) - 1;
 
 	/* Calculate offset to stack_frame & pt_regs */
-	child_stack_sz = ((STACKFRAME_SZ + TRACEREG_SZ) +
-			  (kernel_thread ? STACKFRAME_SZ : 0));
+	child_stack_sz = (STACKFRAME_SZ + TRACEREG_SZ);
 	child_trap_frame = (task_stack_page(p) +
 			    (THREAD_SIZE - child_stack_sz));
-	memcpy(child_trap_frame, parent_sf, child_stack_sz);
 
-	__thread_flag_byte_ptr(t)[TI_FLAG_BYTE_CWP] = 
-		(regs->tstate + 1) & TSTATE_CWP;
 	t->new_child = 1;
 	t->ksp = ((unsigned long) child_trap_frame) - STACK_BIAS;
 	t->kregs = (struct pt_regs *) (child_trap_frame +
 				       sizeof(struct sparc_stackf));
 	t->fpsaved[0] = 0;
 
-	if (kernel_thread) {
-		struct sparc_stackf *child_sf = (struct sparc_stackf *)
-			(child_trap_frame + (STACKFRAME_SZ + TRACEREG_SZ));
-
-		/* Zero terminate the stack backtrace.  */
-		child_sf->fp = NULL;
-		t->kregs->u_regs[UREG_FP] =
-		  ((unsigned long) child_sf) - STACK_BIAS;
-
+	if (unlikely(p->flags & PF_KTHREAD)) {
+		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->current_ds = ASI_P;
-		t->kregs->u_regs[UREG_G6] = (unsigned long) t;
-		t->kregs->u_regs[UREG_G4] = (unsigned long) t->task;
-	} else {
-		if (t->flags & _TIF_32BIT) {
-			sp &= 0x00000000ffffffffUL;
-			regs->u_regs[UREG_FP] &= 0x00000000ffffffffUL;
-		}
-		t->kregs->u_regs[UREG_FP] = sp;
-		t->current_ds = ASI_AIUS;
-		if (sp != regs->u_regs[UREG_FP]) {
-			unsigned long csp;
-
-			csp = clone_stackframe(sp, regs->u_regs[UREG_FP]);
-			if (!csp)
-				return -EFAULT;
-			t->kregs->u_regs[UREG_FP] = csp;
-		}
-		if (t->utraps)
-			t->utraps[0]++;
+		t->kregs->u_regs[UREG_G1] = sp; /* function */
+		t->kregs->u_regs[UREG_G2] = arg;
+		return 0;
 	}
 
+	parent_sf = ((struct sparc_stackf *) regs) - 1;
+	memcpy(child_trap_frame, parent_sf, child_stack_sz);
+	if (t->flags & _TIF_32BIT) {
+		sp &= 0x00000000ffffffffUL;
+		regs->u_regs[UREG_FP] &= 0x00000000ffffffffUL;
+	}
+	t->kregs->u_regs[UREG_FP] = sp;
+	__thread_flag_byte_ptr(t)[TI_FLAG_BYTE_CWP] = 
+		(regs->tstate + 1) & TSTATE_CWP;
+	t->current_ds = ASI_AIUS;
+	if (sp != regs->u_regs[UREG_FP]) {
+		unsigned long csp;
+
+		csp = clone_stackframe(sp, regs->u_regs[UREG_FP]);
+		if (!csp)
+			return -EFAULT;
+		t->kregs->u_regs[UREG_FP] = csp;
+	}
+	if (t->utraps)
+		t->utraps[0]++;
+
 	/* Set the return value for the child. */
 	t->kregs->u_regs[UREG_I0] = current->pid;
 	t->kregs->u_regs[UREG_I1] = 1;
@@ -609,45 +601,6 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
 	return 0;
 }
 
-/*
- * This is the mechanism for creating a new kernel thread.
- *
- * NOTE! Only a kernel-only process(ie the swapper or direct descendants
- * who haven't done an "execve()") should use this: it will work within
- * a system call from a "real" process, but the process memory space will
- * not be freed until both the parent and the child have exited.
- */
-pid_t kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
-{
-	long retval;
-
-	/* If the parent runs before fn(arg) is called by the child,
-	 * the input registers of this function can be clobbered.
-	 * So we stash 'fn' and 'arg' into global registers which
-	 * will not be modified by the parent.
-	 */
-	__asm__ __volatile__("mov %4, %%g2\n\t"	   /* Save FN into global */
-			     "mov %5, %%g3\n\t"	   /* Save ARG into global */
-			     "mov %1, %%g1\n\t"	   /* Clone syscall nr. */
-			     "mov %2, %%o0\n\t"	   /* Clone flags. */
-			     "mov 0, %%o1\n\t"	   /* usp arg == 0 */
-			     "t 0x6d\n\t"	   /* Linux/Sparc clone(). */
-			     "brz,a,pn %%o1, 1f\n\t" /* Parent, just return. */
-			     " mov %%o0, %0\n\t"
-			     "jmpl %%g2, %%o7\n\t"   /* Call the function. */
-			     " mov %%g3, %%o0\n\t"   /* Set arg in delay. */
-			     "mov %3, %%g1\n\t"
-			     "t 0x6d\n\t"	   /* Linux/Sparc exit(). */
-			     /* Notreached by child. */
-			     "1:" :
-			     "=r" (retval) :
-			     "i" (__NR_clone), "r" (flags | CLONE_VM | CLONE_UNTRACED),
-			     "i" (__NR_exit),  "r" (fn), "r" (arg) :
-			     "g1", "g2", "g3", "o0", "o1", "memory", "cc");
-	return retval;
-}
-EXPORT_SYMBOL(kernel_thread);
-
 typedef struct {
 	union {
 		unsigned int	pr_regs[32];

arch/sparc/kernel/syscalls.S

@@ -112,11 +112,16 @@ sys_clone:
 ret_from_syscall:
 	/* Clear current_thread_info()->new_child. */
 	stb	%g0, [%g6 + TI_NEW_CHILD]
-	ldx	[%g6 + TI_FLAGS], %l0
 	call	schedule_tail
 	 mov	%g7, %o0
-	ba,pt	%xcc, ret_sys_call
-	 ldx	[%sp + PTREGS_OFF + PT_V9_I0], %o0
+	ldx	[%sp + PTREGS_OFF + PT_V9_I0], %o0
+	brnz,a,pt	%o0, ret_sys_call
+	 ldx	[%g6 + TI_FLAGS], %l0
+	ldx	[%sp + PTREGS_OFF + PT_V9_G1], %l0
+	call	%l0
+	 ldx	[%sp + PTREGS_OFF + PT_V9_G2], %o0
+	call	do_exit	! will not return
+	 mov	0,%o0
 
 	.globl	sparc_exit
 	.type	sparc_exit,#function