src/ucontext/arm64/_ctx_start.s

   1 /*
   2  * Copyright (c) 2020 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_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. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24 #include "asm_help.h"
  25 #include <os/tsd.h>
  26 #include <TargetConditionals.h>
  27
  28 .text
  29
  30 #if TARGET_OS_OSX || TARGET_OS_DRIVERKIT
  31
  32 /* Helper macro for unmunging pointers in place */
  33 .macro PTR_UNMUNGE addr
  34 #if defined(__LP64__)
  35         _OS_PTR_MUNGE_TOKEN(x16, x16)
  36 #else
  37         _OS_PTR_MUNGE_TOKEN(x16, w16)
  38 #endif
  39         _OS_PTR_UNMUNGE(\addr, \addr, x16)
  40 .endmacro
  41
  42 .macro CALL_USER_FUNC func
  43         // Populate the first 8 arguments in registers from the stack. Coordinated
  44         // with makecontext which populates the arguments on the stack
  45         ldp w0, w1, [sp], #32
  46         ldp w2, w3, [sp, #-24]
  47         ldp w4, w5, [sp, #-16]
  48         ldp w6, w7, [sp, #-8]
  49
  50         PTR_UNMUNGE \func
  51
  52 #if defined(__arm64e__)
  53         blraaz  \func
  54 #else
  55         blr     \func
  56 #endif
  57 .endmacro
  58
  59 .private_extern __ctx_start
  60 .align 2
  61 __ctx_start:
  62         /* x20 = munged signed user func,
  63          * x19 = uctx,
  64          * fp = top of stack,
  65          * sp = where args end */
  66         CALL_USER_FUNC x20
  67
  68         /* user function returned, set up stack for _ctx_done */
  69
  70         /* Reset to top of stack */
  71         mov             sp, fp
  72
  73         mov             x0, x19 /* x0 = uctx */
  74         bl              __ctx_done
  75
  76         brk             #666    /* Should not get here */
  77
  78 #endif