powerpc: switch to saner kernel_execve() semantics

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

arch/powerpc/Kconfig

@@ -144,6 +144,7 @@ config PPC
 	select GENERIC_KERNEL_THREAD
 	select HAVE_MOD_ARCH_SPECIFIC
 	select MODULES_USE_ELF_RELA
+	select GENERIC_KERNEL_EXECVE
 
 config EARLY_PRINTK
 	bool

arch/powerpc/include/asm/unistd.h

@@ -56,7 +56,6 @@
 #define __ARCH_WANT_COMPAT_SYS_SENDFILE
 #endif
 #define __ARCH_WANT_SYS_EXECVE
-#define __ARCH_WANT_KERNEL_EXECVE
 
 /*
  * "Conditional" syscalls

arch/powerpc/kernel/entry_32.S

@@ -444,11 +444,6 @@ ret_from_kernel_thread:
 	PPC440EP_ERR42
 	blrl
 	li	r3,0
-	b	do_exit		# no return
-
-	.globl	__ret_from_kernel_execve
-__ret_from_kernel_execve:
-	addi	r1,r3,-STACK_FRAME_OVERHEAD
 	b	ret_from_syscall
 
 /* Traced system call support */

arch/powerpc/kernel/entry_64.S

@@ -378,12 +378,6 @@ _GLOBAL(ret_from_kernel_thread)
 	mr	r3,r15
 	blrl
 	li	r3,0
-	b	.do_exit	# no return
-
-_GLOBAL(__ret_from_kernel_execve)
-	addi	r1,r3,-STACK_FRAME_OVERHEAD
-	li	r10,1
-	std	r10,SOFTE(r1)
 	b	syscall_exit
 
 	.section	".toc","aw"

arch/powerpc/kernel/process.c

@@ -746,19 +746,21 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
 	sp -= sizeof(struct pt_regs);
 	childregs = (struct pt_regs *) sp;
 	if (!regs) {
-		/* for kernel thread, set `current' and stackptr in new task */
+		struct thread_info *ti = (void *)task_stack_page(p);
 		memset(childregs, 0, sizeof(struct pt_regs));
 		childregs->gpr[1] = sp + sizeof(struct pt_regs);
 #ifdef CONFIG_PPC64
 		childregs->gpr[14] = *(unsigned long *)usp;
 		childregs->gpr[2] = ((unsigned long *)usp)[1],
 		clear_tsk_thread_flag(p, TIF_32BIT);
+		childregs->softe = 1;
 #else
 		childregs->gpr[14] = usp;	/* function */
 		childregs->gpr[2] = (unsigned long) p;
 #endif
 		childregs->gpr[15] = arg;
 		p->thread.regs = NULL;	/* no user register state */
+		ti->flags |= _TIF_RESTOREALL;
 		f = ret_from_kernel_thread;
 	} else {
 		CHECK_FULL_REGS(regs);
@@ -1063,15 +1065,6 @@ int sys_vfork(unsigned long p1, unsigned long p2, unsigned long p3,
 			regs, 0, NULL, NULL);
 }
 
-void __ret_from_kernel_execve(struct pt_regs *normal)
-__noreturn;
-
-void ret_from_kernel_execve(struct pt_regs *normal)
-{
-	set_thread_flag(TIF_RESTOREALL);
-	__ret_from_kernel_execve(normal);
-}
-
 static inline int valid_irq_stack(unsigned long sp, struct task_struct *p,
 				  unsigned long nbytes)
 {