libsyscall/custom/__getpid.s

   1 /*
   2  * Copyright (c) 1999-2007 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28
  29 #include "SYS.h"
  30
  31 #if defined(__i386__)
  32
  33         .data
  34         .private_extern __current_pid
  35 L__current_pid_addr:
  36  __current_pid:
  37         .long 0
  38
  39 #if defined(__DYNAMIC__)
  40 #define GET_CURRENT_PID                         \
  41         call    0f                              ; \
  42 0:                                              ; \
  43         popl    %ecx                            ; \
  44         leal    L__current_pid_addr-0b(%ecx), %ecx
  45
  46 #define __current_pid (%ecx)
  47
  48 #else
  49 #define GET_CURRENT_PID
  50 #endif
  51
  52 /*
  53  * If __current_pid is > 0, return it, else make syscall.
  54  * If __current_pid is 0, cache result of syscall.
  55  */
  56 TEXT
  57 LEAF(___getpid, 0)
  58         GET_CURRENT_PID
  59         movl            __current_pid, %eax
  60         testl           %eax, %eax
  61         jle             1f
  62         ret
  63 1:
  64         UNIX_SYSCALL_NONAME(getpid, 0, cerror_nocancel)
  65         movl            %eax, %edx
  66         xorl            %eax, %eax
  67         GET_CURRENT_PID
  68         lock
  69         cmpxchgl        %edx, __current_pid
  70         movl            %edx, %eax
  71         ret
  72
  73 #elif defined(__x86_64__)
  74
  75         .data
  76         .private_extern __current_pid
  77 __current_pid:
  78         .long 0
  79
  80 /*
  81  * If __current_pid is > 0, return it, else make syscall.
  82  * If __current_pid is 0, cache result of syscall.
  83  */
  84 TEXT
  85 LEAF(___getpid, 0)
  86         movl    __current_pid(%rip), %eax
  87         testl   %eax, %eax
  88         jle             1f
  89         ret
  90 1:
  91         UNIX_SYSCALL_NONAME(getpid, 0, cerror_nocancel)
  92         movl            %eax, %edx
  93         xorl            %eax, %eax
  94         leaq            __current_pid(%rip), %rcx
  95         lock
  96         cmpxchgl        %edx, (%rcx)
  97         movl            %edx, %eax
  98         ret
  99
 100 #elif defined(__arm__)
 101
 102 #include <arm/arch.h>
 103
 104         .data
 105         .globl  __current_pid
 106         .align 2
 107 __current_pid:
 108         /* Cached pid.  Possible values:
 109          *      0:              no value cached
 110          *      > 0:            cached PID of current process
 111          *      < 0:            negative number of vforks in progress
 112          *      INT_MIN:        for pre-ARMv6, "looking" value (0x80000000)
 113          */
 114         .long 0
 115
 116 MI_ENTRY_POINT(___getpid)
 117         ldr     r3, L__current_pid
 118 L1:     add     r3, pc, r3              // r3 = &__current_pid
 119         ldr     r0, [r3]                // get the cached pid
 120         cmp     r0, #0
 121         bxgt    lr                      // if positive, return it
 122
 123         SYSCALL_NONAME(getpid, 0, cerror_nocancel)
 124
 125 #ifdef _ARM_ARCH_6
 126         ldrex   r2, [r3]                // see if we can cache it
 127         cmp     r2, #0                  // we can't if there are any...
 128         bxlt    lr                      // ...vforks in progress
 129         strex   r2, r0, [r3]            // ignore conflicts
 130 #else
 131         mov     r1, #0x80000000         // load "looking" value
 132         swp     r2, r1, [r3]            // look at the value, lock others out
 133         cmp     r2, r1                  // anyone else trying to look?
 134         bxeq    lr                      // yes, so return immediately/
 135         cmp     r2, #0                  // see if we can cache it
 136         streq   r0, [r3]                // if zero, we can
 137         strne   r2, [r3]                // otherwise restore previous value
 138 #endif
 139
 140         bx      lr
 141
 142 L__current_pid:
 143         .long   __current_pid - (L1+8)
 144
 145 #elif defined(__arm64__)
 146         .data
 147         .globl  __current_pid
 148         .align 2
 149 __current_pid:
 150         /* cached pid.  possible values:
 151          *      0:              no value cached
 152          *      > 0:            cached pid of current process
 153          *      < 0:            negative number of vforks in progress
 154          *      int_min:        for pre-armv6, "looking" value (0x80000000)
 155          */
 156         .long 0
 157
 158 MI_ENTRY_POINT(___getpid)
 159         MI_GET_ADDRESS(x9, __current_pid)       // Get address of cached value
 160         ldr             w0, [x9]                                        // Load it
 161         cmp             w0, #0                                          // See if there's a cached value
 162         b.le    L_notcached                                     // If not, make syscall
 163         ret                                                                     // Else, we're done
 164 L_notcached:
 165         SYSCALL_NONAME(getpid, 0, cerror_nocancel)
 166         ldxr    w10, [x9]                                       // Exclusive load
 167         cbnz    w10, L_done                                     // Unless unset, don't even try
 168         stxr    wzr, w0, [x9]                           // Try to store, but don't care if we fail (someone will win, or not)
 169 L_done:
 170         ret                                                                     // Done
 171 #else
 172 #error Unsupported architecture
 173 #endif