unicore32: switch to generic kernel_thread()/kernel_execve()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-and-Tested-by: Guan Xuetao <gxt@mprc.pku.edu.cn>

arch/unicore32/Kconfig

@@ -16,6 +16,8 @@ config UNICORE32
 	select ARCH_WANT_FRAME_POINTERS
 	select GENERIC_IOMAP
 	select MODULES_USE_ELF_REL
+	select GENERIC_KERNEL_THREAD
+	select GENERIC_KERNEL_EXECVE
 	help
 	  UniCore-32 is 32-bit Instruction Set Architecture,
 	  including a series of low-power-consumption RISC chip

arch/unicore32/include/asm/processor.h

@@ -72,11 +72,6 @@ unsigned long get_wchan(struct task_struct *p);
 
 #define cpu_relax()			barrier()
 
-/*
- * Create a new kernel thread
- */
-extern int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
-
 #define task_pt_regs(p) \
 	((struct pt_regs *)(THREAD_START_SP + task_stack_page(p)) - 1)
 

arch/unicore32/kernel/entry.S

@@ -573,17 +573,16 @@ ENDPROC(ret_to_user)
  */
 ENTRY(ret_from_fork)
 	b.l	schedule_tail
-	get_thread_info tsk
-	ldw	r1, [tsk+], #TI_FLAGS		@ check for syscall tracing
-	mov	why, #1
-	cand.a	r1, #_TIF_SYSCALL_TRACE		@ are we tracing syscalls?
-	beq	ret_slow_syscall
-	mov	r1, sp
-	mov	r0, #1				@ trace exit [IP = 1]
-	b.l	syscall_trace
 	b	ret_slow_syscall
 ENDPROC(ret_from_fork)
 
+ENTRY(ret_from_kernel_thread)
+	b.l	schedule_tail
+	mov	r0, r5
+	adr	lr, ret_slow_syscall
+	mov	pc, r4
+ENDPROC(ret_from_kernel_thread)
+
 /*=============================================================================
  * SWI handler
  *-----------------------------------------------------------------------------

arch/unicore32/kernel/process.c

@@ -258,6 +258,7 @@ void release_thread(struct task_struct *dead_task)
 }
 
 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
+asmlinkage void ret_from_kernel_thread(void) __asm__("ret_from_kernel_thread");
 
 int
 copy_thread(unsigned long clone_flags, unsigned long stack_start,
@@ -266,17 +267,22 @@ copy_thread(unsigned long clone_flags, unsigned long stack_start,
 	struct thread_info *thread = task_thread_info(p);
 	struct pt_regs *childregs = task_pt_regs(p);
 
-	*childregs = *regs;
-	childregs->UCreg_00 = 0;
-	childregs->UCreg_sp = stack_start;
-
 	memset(&thread->cpu_context, 0, sizeof(struct cpu_context_save));
 	thread->cpu_context.sp = (unsigned long)childregs;
+	if (unlikely(!regs)) {
+		thread->cpu_context.pc = (unsigned long)ret_from_kernel_thread;
+		thread->cpu_context.r4 = stack_start;
+		thread->cpu_context.r5 = stk_sz;
+		memset(childregs, 0, sizeof(struct pt_regs));
+	} else {
 		thread->cpu_context.pc = (unsigned long)ret_from_fork;
+		*childregs = *regs;
+		childregs->UCreg_00 = 0;
+		childregs->UCreg_sp = stack_start;
 
 		if (clone_flags & CLONE_SETTLS)
 			childregs->UCreg_16 = regs->UCreg_03;
-
+	}
 	return 0;
 }
 
@@ -305,42 +311,6 @@ int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fp)
 }
 EXPORT_SYMBOL(dump_fpu);
 
-/*
- * Shuffle the argument into the correct register before calling the
- * thread function.  r1 is the thread argument, r2 is the pointer to
- * the thread function, and r3 points to the exit function.
- */
-asm(".pushsection .text\n"
-"	.align\n"
-"	.type	kernel_thread_helper, #function\n"
-"kernel_thread_helper:\n"
-"	mov.a	asr, r7\n"
-"	mov	r0, r4\n"
-"	mov	lr, r6\n"
-"	mov	pc, r5\n"
-"	.size	kernel_thread_helper, . - kernel_thread_helper\n"
-"	.popsection");
-
-/*
- * Create a kernel thread.
- */
-pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
-{
-	struct pt_regs regs;
-
-	memset(&regs, 0, sizeof(regs));
-
-	regs.UCreg_04 = (unsigned long)arg;
-	regs.UCreg_05 = (unsigned long)fn;
-	regs.UCreg_06 = (unsigned long)do_exit;
-	regs.UCreg_07 = PRIV_MODE;
-	regs.UCreg_pc = (unsigned long)kernel_thread_helper;
-	regs.UCreg_asr = regs.UCreg_07 | PSR_I_BIT;
-
-	return do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
-}
-EXPORT_SYMBOL(kernel_thread);
-
 unsigned long get_wchan(struct task_struct *p)
 {
 	struct stackframe frame;

arch/unicore32/kernel/sys.c

@@ -63,48 +63,6 @@ asmlinkage long __sys_execve(const char __user *filename,
 	return error;
 }
 
-int kernel_execve(const char *filename,
-		  const char *const argv[],
-		  const char *const envp[])
-{
-	struct pt_regs regs;
-	int ret;
-
-	memset(&regs, 0, sizeof(struct pt_regs));
-	ret = do_execve(filename,
-			(const char __user *const __user *)argv,
-			(const char __user *const __user *)envp, &regs);
-	if (ret < 0)
-		goto out;
-
-	/*
-	 * Save argc to the register structure for userspace.
-	 */
-	regs.UCreg_00 = ret;
-
-	/*
-	 * We were successful.  We won't be returning to our caller, but
-	 * instead to user space by manipulating the kernel stack.
-	 */
-	asm("add	r0, %0, %1\n\t"
-		"mov	r1, %2\n\t"
-		"mov	r2, %3\n\t"
-		"mov	r22, #0\n\t"	/* not a syscall */
-		"mov	r23, %0\n\t"	/* thread structure */
-		"b.l	memmove\n\t"	/* copy regs to top of stack */
-		"mov	sp, r0\n\t"	/* reposition stack pointer */
-		"b	ret_to_user"
-		:
-		: "r" (current_thread_info()),
-		  "Ir" (THREAD_START_SP - sizeof(regs)),
-		  "r" (&regs),
-		  "Ir" (sizeof(regs))
-		: "r0", "r1", "r2", "r3", "ip", "lr", "memory");
-
- out:
-	return ret;
-}
-
 /* Note: used by the compat code even in 64-bit Linux. */
 SYSCALL_DEFINE6(mmap2, unsigned long, addr, unsigned long, len,
 		unsigned long, prot, unsigned long, flags,