alpha: switch to saner kernel_execve() semantics

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

arch/alpha/Kconfig

@@ -21,6 +21,7 @@ config ALPHA
 	select GENERIC_STRNCPY_FROM_USER
 	select GENERIC_STRNLEN_USER
 	select GENERIC_KERNEL_THREAD
+	select GENERIC_KERNEL_EXECVE
 	help
 	  The Alpha is a 64-bit general-purpose processor designed and
 	  marketed by the Digital Equipment Corporation of blessed memory,

arch/alpha/include/asm/unistd.h

@@ -482,7 +482,6 @@
 #define __ARCH_WANT_SYS_SIGPENDING
 #define __ARCH_WANT_SYS_RT_SIGSUSPEND
 #define __ARCH_WANT_SYS_EXECVE
-#define __ARCH_WANT_KERNEL_EXECVE
 
 /* "Conditional" syscalls.  What we want is
 

arch/alpha/kernel/entry.S

@@ -603,24 +603,9 @@ ret_from_kernel_thread:
 	mov	$9, $27
 	mov	$10, $16
 	jsr	$26, ($9)
-	ldgp	$gp, 0($26)
-	mov	$0, $16
-	mov	$31, $26
-	jmp	$31, sys_exit
-.end ret_from_kernel_thread
-
-	.globl	ret_from_kernel_execve
-	.align	4
-	.ent	ret_from_kernel_execve
-ret_from_kernel_execve:
-	mov	$16, $sp
-	/* Avoid the HAE being gratuitously wrong, to avoid restoring it.  */
-	ldq	$2, alpha_mv+HAE_CACHE
-	stq	$2, 152($sp)		/* HAE */
 	mov	$31, $19		/* to disable syscall restarts */
 	br	$31, ret_to_user
-
-.end	ret_from_kernel_execve
+.end ret_from_kernel_thread
 
 
 /*