score: switch to generic kernel_thread()/kernel_execve()

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

arch/score/Kconfig

@@ -13,6 +13,8 @@ config SCORE
        select GENERIC_CLOCKEVENTS
        select HAVE_MOD_ARCH_SPECIFIC
 	select MODULES_USE_ELF_REL
+	select GENERIC_KERNEL_THREAD
+	select GENERIC_KERNEL_EXECVE
 
 choice
 	prompt "System type"

arch/score/include/asm/processor.h

@@ -13,7 +13,6 @@ struct task_struct;
  */
 extern void (*cpu_wait)(void);
 
-extern long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
 extern unsigned long thread_saved_pc(struct task_struct *tsk);
 extern void start_thread(struct pt_regs *regs,
 			unsigned long pc, unsigned long sp);

arch/score/kernel/entry.S

@@ -278,6 +278,13 @@ need_resched:
 	nop
 #endif
 
+ENTRY(ret_from_kernel_thread)
+	bl	schedule_tail			# r4=struct task_struct *prev
+	nop
+	mv	r4, r13
+	brl	r12
+	j	syscall_exit
+
 ENTRY(ret_from_fork)
 	bl	schedule_tail			# r4=struct task_struct *prev
 

arch/score/kernel/process.c

@@ -60,6 +60,7 @@ void __noreturn cpu_idle(void)
 }
 
 void ret_from_fork(void);
+void ret_from_kernel_thread(void);
 
 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
 {
@@ -86,29 +87,27 @@ void flush_thread(void) {}
  * set up the kernel stack and exception frames for a new process
  */
 int copy_thread(unsigned long clone_flags, unsigned long usp,
-		unsigned long unused,
+		unsigned long arg,
 		struct task_struct *p, struct pt_regs *regs)
 {
 	struct thread_info *ti = task_thread_info(p);
 	struct pt_regs *childregs = task_pt_regs(p);
 
-	p->set_child_tid = NULL;
-	p->clear_child_tid = NULL;
-
-	*childregs = *regs;
-	childregs->regs[7] = 0;		/* Clear error flag */
-	childregs->regs[4] = 0;		/* Child gets zero as return value */
-	regs->regs[4] = p->pid;
-
-	if (childregs->cp0_psr & 0x8) {	/* test kernel fork or user fork */
-		childregs->regs[0] = usp;		/* user fork */
+	p->thread.reg0 = (unsigned long) childregs;
+	if (unlikely(!regs)) {
+		memset(childregs, 0, sizeof(struct pt_regs));
+		p->thread->reg12 = usp;
+		p->thread->reg13 = arg;
+		p->thread.reg3 = (unsigned long) ret_from_kernel_thread;
 	} else {
-		childregs->regs[28] = (unsigned long) ti; /* kernel fork */
-		childregs->regs[0] = (unsigned long) childregs;
+		*childregs = *regs;
+		childregs->regs[7] = 0;		/* Clear error flag */
+		childregs->regs[4] = 0;		/* Child gets zero as return value */
+		childregs->regs[0] = usp;	/* user fork */
+		regs->regs[4] = p->pid;		/* WTF? */
+		p->thread.reg3 = (unsigned long) ret_from_fork;
 	}
 
-	p->thread.reg0 = (unsigned long) childregs;
-	p->thread.reg3 = (unsigned long) ret_from_fork;
 	p->thread.cp0_psr = 0;
 
 	return 0;
@@ -120,32 +119,6 @@ int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
 	return 1;
 }
 
-static void __noreturn
-kernel_thread_helper(void *unused0, int (*fn)(void *),
-		 void *arg, void *unused1)
-{
-	do_exit(fn(arg));
-}
-
-/*
- * Create a kernel thread.
- */
-long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
-{
-	struct pt_regs regs;
-
-	memset(&regs, 0, sizeof(regs));
-
-	regs.regs[6] = (unsigned long) arg;
-	regs.regs[5] = (unsigned long) fn;
-	regs.cp0_epc = (unsigned long) kernel_thread_helper;
-	regs.cp0_psr = (regs.cp0_psr & ~(0x1|0x4|0x8)) | \
-			((regs.cp0_psr & 0x3) << 2);
-
-	return do_fork(flags | CLONE_VM | CLONE_UNTRACED, \
-			0, &regs, 0, NULL, NULL);
-}
-
 unsigned long thread_saved_pc(struct task_struct *tsk)
 {
 	return task_pt_regs(tsk)->cp0_epc;

arch/score/kernel/sys_score.c

@@ -107,33 +107,3 @@ score_execve(struct pt_regs *regs)
 	putname(filename);
 	return error;
 }
-
-/*
- * Do a system call from kernel instead of calling sys_execve so we
- * end up with proper pt_regs.
- */
-asmlinkage
-int kernel_execve(const char *filename,
-		  const char *const argv[],
-		  const char *const envp[])
-{
-	register unsigned long __r4 asm("r4") = (unsigned long) filename;
-	register unsigned long __r5 asm("r5") = (unsigned long) argv;
-	register unsigned long __r6 asm("r6") = (unsigned long) envp;
-	register unsigned long __r7 asm("r7");
-
-	__asm__ __volatile__ ("	\n"
-		"ldi	r27, %5		\n"
-		"syscall		\n"
-		"mv	%0, r4		\n"
-		"mv	%1, r7		\n"
-		: "=&r" (__r4), "=r" (__r7)
-		: "r" (__r4), "r" (__r5), "r" (__r6), "i" (__NR_execve)
-		: "r8", "r9", "r10", "r11", "r22", "r23", "r24", "r25",
-		  "r26", "r27", "memory");
-
-	if (__r7 == 0)
-		return __r4;
-
-	return -__r4;
-}