blackfin: convert kernel_thread() and kernel_execve() to generic ones

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

arch/blackfin/Kconfig

@@ -45,6 +45,8 @@ config BLACKFIN
 	select ARCH_USES_GETTIMEOFFSET if !GENERIC_CLOCKEVENTS
 	select HAVE_MOD_ARCH_SPECIFIC
 	select MODULES_USE_ELF_RELA
+	select GENERIC_KERNEL_THREAD
+	select GENERIC_KERNEL_EXECVE
 
 config GENERIC_CSUM
 	def_bool y

arch/blackfin/include/asm/processor.h

@@ -75,8 +75,6 @@ static inline void release_thread(struct task_struct *dead_task)
 {
 }
 
-extern int kernel_thread(int (*fn) (void *), void *arg, unsigned long flags);
-
 /*
  * Free current thread data structures etc..
  */

arch/blackfin/kernel/entry.S

@@ -46,22 +46,16 @@ ENTRY(_ret_from_fork)
 	SP += -12;
 	pseudo_long_call _schedule_tail, p5;
 	SP += 12;
-	r0 = [sp + PT_IPEND];
-	cc = bittst(r0,1);
-	if cc jump .Lin_kernel;
+	p1 = [sp++];
+	r0 = [sp++];
+	cc = p1 == 0;
+	if cc jump .Lfork;
+	sp += -12;
+	call (p1);
+	sp += 12;
+.Lfork:
 	RESTORE_CONTEXT
 	rti;
-.Lin_kernel:
-	bitclr(r0,1);
-	[sp + PT_IPEND] = r0;
-	/* do a 'fake' RTI by jumping to [RETI]
-	 * to avoid clearing supervisor mode in child
-	 */
-	r0 = [sp + PT_PC];
-	[sp + PT_P0] = r0;
-
-	RESTORE_ALL_SYS
-	jump (p0);
 ENDPROC(_ret_from_fork)
 
 ENTRY(_sys_vfork)

arch/blackfin/kernel/process.c

@@ -101,40 +101,6 @@ void cpu_idle(void)
 	}
 }
 
-/*
- * This gets run with P1 containing the
- * function to call, and R1 containing
- * the "args".  Note P0 is clobbered on the way here.
- */
-void kernel_thread_helper(void);
-__asm__(".section .text\n"
-	".align 4\n"
-	"_kernel_thread_helper:\n\t"
-	"\tsp += -12;\n\t"
-	"\tr0 = r1;\n\t" "\tcall (p1);\n\t" "\tcall _do_exit;\n" ".previous");
-
-/*
- * 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.r1 = (unsigned long)arg;
-	regs.p1 = (unsigned long)fn;
-	regs.pc = (unsigned long)kernel_thread_helper;
-	regs.orig_p0 = -1;
-	/* Set bit 2 to tell ret_from_fork we should be returning to kernel
-	   mode.  */
-	regs.ipend = 0x8002;
-	__asm__ __volatile__("%0 = syscfg;":"=da"(regs.syscfg):);
-	return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL,
-		       NULL);
-}
-EXPORT_SYMBOL(kernel_thread);
-
 /*
  * Do necessary setup to start up a newly executed thread.
  *
@@ -193,13 +159,26 @@ copy_thread(unsigned long clone_flags,
 	    struct task_struct *p, struct pt_regs *regs)
 {
 	struct pt_regs *childregs;
+	unsigned long *v;
 
 	childregs = (struct pt_regs *) (task_stack_page(p) + THREAD_SIZE) - 1;
+	v = ((unsigned long *)childregs) - 2;
+	if (unlikely(!regs)) {
+		memset(childregs, 0, sizeof(struct pt_regs));
+		v[0] = usp;
+		v[1] = topstk;
+		childregs->orig_p0 = -1;
+		childregs->ipend = 0x8000;
+		__asm__ __volatile__("%0 = syscfg;":"=da"(childregs->syscfg):);
+		p->thread.usp = 0;
+	} else {
 		*childregs = *regs;
 		childregs->r0 = 0;
-
 		p->thread.usp = usp;
-	p->thread.ksp = (unsigned long)childregs;
+		v[0] = v[1] = 0;
+	}
+
+	p->thread.ksp = (unsigned long)v;
 	p->thread.pc = (unsigned long)ret_from_fork;
 
 	return 0;

arch/blackfin/mach-common/entry.S

@@ -530,61 +530,6 @@ ENTRY(_trap) /* Exception: 4th entry into system event table(supervisor mode)*/
 	jump .Lsyscall_really_exit;
 ENDPROC(_trap)
 
-ENTRY(_kernel_execve)
-	link SIZEOF_PTREGS;
-	p0 = sp;
-	r3 = SIZEOF_PTREGS / 4;
-	r4 = 0(x);
-.Lclear_regs:
-	[p0++] = r4;
-	r3 += -1;
-	cc = r3 == 0;
-	if !cc jump .Lclear_regs (bp);
-
-	p0 = sp;
-	sp += -16;
-	[sp + 12] = p0;
-	pseudo_long_call _do_execve, p5;
-	SP += 16;
-	cc = r0 == 0;
-	if ! cc jump .Lexecve_failed;
-	/* Success.  Copy our temporary pt_regs to the top of the kernel
-	 * stack and do a normal exception return.
-	 */
-	r1 = sp;
-	r0 = (-KERNEL_STACK_SIZE) (x);
-	r1 = r1 & r0;
-	p2 = r1;
-	p3 = [p2];
-	r0 = KERNEL_STACK_SIZE - 4 (z);
-	p1 = r0;
-	p1 = p1 + p2;
-
-	p0 = fp;
-	r4 = [p0--];
-	r3 = SIZEOF_PTREGS / 4;
-.Lcopy_regs:
-	r4 = [p0--];
-	[p1--] = r4;
-	r3 += -1;
-	cc = r3 == 0;
-	if ! cc jump .Lcopy_regs (bp);
-
-	r0 = (KERNEL_STACK_SIZE - SIZEOF_PTREGS) (z);
-	p1 = r0;
-	p1 = p1 + p2;
-	sp = p1;
-	r0 = syscfg;
-	[SP + PT_SYSCFG] = r0;
-	[p3 + (TASK_THREAD + THREAD_KSP)] = sp;
-
-	RESTORE_CONTEXT;
-	rti;
-.Lexecve_failed:
-	unlink;
-	rts;
-ENDPROC(_kernel_execve)
-
 ENTRY(_system_call)
 	/* Store IPEND */
 	p2.l = lo(IPEND);