/*
* Copyright (c) 1999-2007 Apple Inc. All rights reserved.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_START@
*
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. The rights granted to you under the License
* may not be used to create, or enable the creation or redistribution of,
* unlawful or unlicensed copies of an Apple operating system, or to
* circumvent, violate, or enable the circumvention or violation of, any
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*
* Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this file.
*
* The Original Code and all software distributed under the License are
* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
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*/
/* Copyright (c) 1998 Apple Computer, Inc. All rights reserved.
*
* File: libc/ppc/sys/vfork.s
*
* HISTORY
* 23-Jun-1998 Umesh Vaishampayan (umeshv@apple.com)
* Created from fork.s
*
*/
#include "SYS.h"
#if defined(__i386__)
#if defined(__DYNAMIC__)
#define GET_CURRENT_PID PICIFY(__current_pid)
NON_LAZY_STUB(__current_pid)
#define __current_pid (%edx)
#else
#define GET_CURRENT_PID
#endif
/*
* If __current_pid >= 0, we want to put a -1 in there
* otherwise we just decrement it
*/
LEAF(___vfork, 0)
GET_CURRENT_PID
movl __current_pid, %eax
0:
xorl %ecx, %ecx
testl %eax, %eax
cmovs %eax, %ecx
decl %ecx
lock
cmpxchgl %ecx, __current_pid
jne 0b
popl %ecx
movl $(SYS_vfork), %eax // code for vfork -> eax
UNIX_SYSCALL_TRAP // do the system call
jnb L1 // jump if CF==0
GET_CURRENT_PID
lock
incl __current_pid
pushl %ecx
BRANCH_EXTERN(tramp_cerror)
L1:
testl %edx, %edx // CF=OF=0, ZF set if zero result
jz L2 // parent, since r1 == 0 in parent, 1 in child
xorl %eax, %eax // zero eax
jmp *%ecx
L2:
GET_CURRENT_PID
lock
incl __current_pid
jmp *%ecx
#elif defined(__x86_64__)
/*
* If __current_pid >= 0, we want to put a -1 in there
* otherwise we just decrement it
*/
LEAF(___vfork, 0)
movq __current_pid@GOTPCREL(%rip), %rax
movl (%rax), %eax
0:
xorl %ecx, %ecx
testl %eax, %eax
cmovs %eax, %ecx
subl $1, %ecx
movq __current_pid@GOTPCREL(%rip), %rdx
lock
cmpxchgl %ecx, (%rdx)
jne 0b
popq %rdi // return address in %rdi
movq $ SYSCALL_CONSTRUCT_UNIX(SYS_vfork), %rax // code for vfork -> rax
UNIX_SYSCALL_TRAP // do the system call
jnb L1 // jump if CF==0
pushq %rdi // put return address back on stack for cerror
movq __current_pid@GOTPCREL(%rip), %rcx
lock
addl $1, (%rcx)
movq %rax, %rdi
BRANCH_EXTERN(_cerror)
L1:
testl %edx, %edx // CF=OF=0, ZF set if zero result
jz L2 // parent, since r1 == 0 in parent, 1 in child
xorq %rax, %rax // zero rax
jmp *%rdi
L2:
movq __current_pid@GOTPCREL(%rip), %rdx
lock
addl $1, (%rdx)
jmp *%rdi
UNWIND_EPILOGUE
#elif defined(__arm__)
#include <arm/arch.h>
.globl cerror
MI_ENTRY_POINT(___vfork)
MI_GET_ADDRESS(r3, __current_pid) // get address of __current_pid
#ifdef _ARM_ARCH_6
L0:
ldrex r1, [r3]
subs r1, r1, #1 // if __current_pid <= 0, decrement it
movpl r1, #-1 // otherwise put -1 in there
strex r2, r1, [r3]
cmp r2, #0
bne L0
#else
mov r2, #0x80000000 // load "looking" value
L0:
swp r1, r2, [r3] // look at the value, lock others out
cmp r1, r2 // anyone else trying to look?
beq L0 // yes, so wait our turn
subs r1, r1, #1 // if __current_pid <= 0, decrement it
movpl r1, #-1 // otherwise put -1 in there
str r1, [r3]
#endif
mov r1, #1 // prime results
mov r12, #SYS_vfork
swi #SWI_SYSCALL // make the syscall
bcs Lbotch // error?
cmp r1, #0 // parent (r1=0) or child(r1=1)
beq Lparent
//child here...
mov r0, #0
bx lr // return
Lbotch:
stmfd sp!, {lr}
MI_CALL_EXTERNAL(_cerror) // jump here on error
mov r0,#-1 // set the error
// reload values clobbered by cerror (so we can treat them as live in Lparent)
MI_GET_ADDRESS(r3, __current_pid) // get address of __current_pid
ldmfd sp!, {lr}
#ifndef _ARM_ARCH_6
mov r2, #0x80000000 // load "looking" value
#endif
// fall thru
Lparent:
#ifdef _ARM_ARCH_6
ldrex r1, [r3]
add r1, r1, #1 // we're back, decrement vfork count
strex r2, r1, [r3]
cmp r2, #0
bne Lparent
#else
swp r1, r2, [r3] // look at the value, lock others out
cmp r1, r2 // anyone else trying to look?
beq Lparent // yes, so wait our turn
add r1, r1, #1 // we're back, decrement vfork count
str r1, [r3]
#endif
bx lr // return
#elif defined(__arm64__)
MI_ENTRY_POINT(___vfork)
ARM64_STACK_PROLOG
MI_GET_ADDRESS(x9, __current_pid)
Ltry_set_vfork:
ldxr w10, [x9] // Get old current pid value (exclusive)
mov w11, #-1 // Will be -1 if current value is positive
subs w10, w10, #1 // Subtract one
csel w12, w11, w10, pl // If >= 0, set to -1, else set to (current - 1)
stxr w13, w12, [x9] // Attempt exclusive store to current pid
cbnz w13, Ltry_set_vfork // If store failed, retry
// ARM sets r1 to 1 here. I don't see why.
mov w16, #SYS_vfork // Set syscall code
svc #SWI_SYSCALL
b.cs Lbotch
cbz w1, Lparent
// Child
mov w0, #0
ARM64_STACK_EPILOG
// Error case
Lbotch:
PUSH_FRAME
bl _cerror // Update errno
mov w0, #-1 // Set return value
MI_GET_ADDRESS(x9, __current_pid) // Reload current pid address
POP_FRAME
// Fall through
Lparent:
ldxr w10, [x9] // Exclusive load current pid value
add w10, w10, #1 // Increment (i.e. decrement vfork count)
stxr w11, w10, [x9] // Attempt exclusive store of updated vfork count
cbnz w11, Lparent // If exclusive store failed, retry
ARM64_STACK_EPILOG // Done, return
#else
#error Unsupported architecture
#endif