From e0e431aa45416982eb3fddf34cedc72f1c3b3ce3 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Thu, 18 Oct 2012 01:11:58 -0400
Subject: alpha: simplify fork and friends

* no need to restore everything from switch_stack when we only need $26
* no need to pass current_pt_regs() manually, we can just as easily
calculate it in alpha_clone/alpha_vfork ($8 + constant)
* interpretation of zero usp as "use the parent's" is simpler in copy_thread();
let fork and vfork just pass 0.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 arch/alpha/kernel/entry.S | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

(limited to 'arch/alpha/kernel/entry.S')

diff --git a/arch/alpha/kernel/entry.S b/arch/alpha/kernel/entry.S
index a7607832dd4..cc6d34e9e2e 100644
--- a/arch/alpha/kernel/entry.S
+++ b/arch/alpha/kernel/entry.S
@@ -617,7 +617,6 @@ ret_from_kernel_thread:
 	.ent	sys_fork
 sys_fork:
 	.prologue 0
-	mov	$sp, $21
 	bsr	$1, do_switch_stack
 	bis	$31, SIGCHLD, $16
 	mov	$31, $17
@@ -625,7 +624,9 @@ sys_fork:
 	mov	$31, $19
 	mov	$31, $20
 	jsr	$26, alpha_clone
-	bsr	$1, undo_switch_stack
+fork_out:
+	ldq	$26, 56($sp)
+	lda	$sp, SWITCH_STACK_SIZE($sp)
 	ret
 .end sys_fork
 
@@ -634,12 +635,10 @@ sys_fork:
 	.ent	sys_clone
 sys_clone:
 	.prologue 0
-	mov	$sp, $21
 	bsr	$1, do_switch_stack
 	/* $16, $17, $18, $19, $20 come from the user.  */
-	jsr	$26, alpha_clone
-	bsr	$1, undo_switch_stack
-	ret
+	lda	$26, fork_out
+	jsr	$31, alpha_clone
 .end sys_clone
 
 	.align	4
@@ -647,11 +646,9 @@ sys_clone:
 	.ent	sys_vfork
 sys_vfork:
 	.prologue 0
-	mov	$sp, $16
 	bsr	$1, do_switch_stack
-	jsr	$26, alpha_vfork
-	bsr	$1, undo_switch_stack
-	ret
+	lda	$26, fork_out
+	jsr	$31, alpha_vfork
 .end sys_vfork
 
 	.align	4
-- 
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