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Commit e0e431aa authored by Al Viro's avatar Al Viro
Browse files

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: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 2b067fc9

arch/alpha/kernel/entry.S

+7 −10
Original line number Diff line number Diff line
@@ -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

arch/alpha/kernel/process.c

+7 −9
Original line number Diff line number Diff line
@@ -246,19 +246,17 @@ release_thread(struct task_struct *dead_task) 
int

alpha_clone(unsigned long clone_flags, unsigned long usp,

	    int __user *parent_tid, int __user *child_tid,

	    unsigned long tls_value, struct pt_regs *regs)

	    unsigned long tls_value)

{

	if (!usp)

		usp = rdusp();



	return do_fork(clone_flags, usp, regs, 0, parent_tid, child_tid);

	return do_fork(clone_flags, usp, current_pt_regs(), 0,

			parent_tid, child_tid);

}



int

alpha_vfork(struct pt_regs *regs)

alpha_vfork(void)

{

	return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, rdusp(),

		       regs, 0, NULL, NULL);

	return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,

		       current_pt_regs(), 0, NULL, NULL);

}



/*
@@ -301,7 +299,7 @@ copy_thread(unsigned long clone_flags, unsigned long usp, 
	stack = ((struct switch_stack *) regs) - 1;

	*childstack = *stack;

	childstack->r26 = (unsigned long) ret_from_fork;

	childti->pcb.usp = usp;

	childti->pcb.usp = usp ?: rdusp();

	childti->pcb.ksp = (unsigned long) childstack;

	childti->pcb.flags = 1;	/* set FEN, clear everything else */