src/dyldStartup.s

   1 /*
   2  * Copyright (c) 1999-2011 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  * C runtime startup for interface to the dynamic linker.
  25  * This is the same as the entry point in crt0.o with the addition of the
  26  * address of the mach header passed as the an extra first argument.
  27  *
  28  * Kernel sets up stack frame to look like:
  29  *
  30  *      | STRING AREA |
  31  *      +-------------+
  32  *      |      0      |
  33 *       +-------------+
  34  *      |  apple[n]   |
  35  *      +-------------+
  36  *             :
  37  *      +-------------+
  38  *      |  apple[0]   |
  39  *      +-------------+
  40  *      |      0      |
  41  *      +-------------+
  42  *      |    env[n]   |
  43  *      +-------------+
  44  *             :
  45  *             :
  46  *      +-------------+
  47  *      |    env[0]   |
  48  *      +-------------+
  49  *      |      0      |
  50  *      +-------------+
  51  *      | arg[argc-1] |
  52  *      +-------------+
  53  *             :
  54  *             :
  55  *      +-------------+
  56  *      |    arg[0]   |
  57  *      +-------------+
  58  *      |     argc    |
  59  *      +-------------+
  60  * sp-> |      mh     | address of where the a.out's file offset 0 is in memory
  61  *      +-------------+
  62  *
  63  *      Where arg[i] and env[i] point into the STRING AREA
  64  */
  65
  66
  67 #include <TargetConditionals.h>
  68
  69         .globl __dyld_start
  70
  71 #if __i386__ && !TARGET_OS_SIMULATOR
  72         .text
  73         .align  4, 0x90
  74         .globl __dyld_start
  75 __dyld_start:
  76         popl    %edx            # edx = mh of app
  77         pushl   $0              # push a zero for debugger end of frames marker
  78         movl    %esp,%ebp       # pointer to base of kernel frame
  79         andl    $-16,%esp       # force SSE alignment
  80         subl    $32,%esp        # room for locals and outgoing parameters
  81
  82         call    L__dyld_start_picbase
  83 L__dyld_start_picbase:
  84         popl    %ebx            # set %ebx to runtime value of picbase
  85
  86         # call dyldbootstrap::start(app_mh, argc, argv, dyld_mh, &startGlue)
  87         subl    $L__dyld_start_picbase-__dyld_start, %ebx # ebx = &__dyld_start
  88         subl    $0x1000, %ebx   # ebx = load address of dyld
  89         movl    %edx,(%esp)     # param1 = app_mh
  90         movl    4(%ebp),%eax
  91         movl    %eax,4(%esp)    # param2 = argc
  92         lea     8(%ebp),%eax
  93         movl    %eax,8(%esp)    # param3 = argv
  94         movl    %ebx,12(%esp)   # param4 = dyld load address
  95         lea     28(%esp),%eax
  96         movl    %eax,16(%esp)   # param5 = &startGlue
  97         call    __ZN13dyldbootstrap5startEPKN5dyld311MachOLoadedEiPPKcS3_Pm
  98         movl    28(%esp),%edx
  99         cmpl    $0,%edx
 100         jne     Lnew
 101
 102         # clean up stack and jump to "start" in main executable
 103         movl    %ebp,%esp       # restore the unaligned stack pointer
 104         addl    $4,%esp         # remove debugger end frame marker
 105         movl    $0,%ebp         # restore ebp back to zero
 106         jmp     *%eax           # jump to the entry point
 107
 108         # LC_MAIN case, set up stack for call to main()
 109 Lnew:   movl    4(%ebp),%ebx
 110         movl    %ebx,(%esp)     # main param1 = argc
 111         leal    8(%ebp),%ecx
 112         movl    %ecx,4(%esp)    # main param2 = argv
 113         leal    0x4(%ecx,%ebx,4),%ebx
 114         movl    %ebx,8(%esp)    # main param3 = env
 115 Lapple: movl    (%ebx),%ecx     # look for NULL ending env[] array
 116         add     $4,%ebx
 117         testl   %ecx,%ecx
 118         jne     Lapple          # once found, next pointer is "apple" parameter now in %ebx
 119         movl    %ebx,12(%esp)   # main param4 = apple
 120         pushl   %edx            # simulate return address into _start in libdyld
 121         jmp     *%eax           # jump to main(argc,argv,env,apple) with return address set to _start
 122
 123 #endif /* __i386__  && !TARGET_OS_SIMULATOR*/
 124
 125
 126
 127 #if __x86_64__ && !TARGET_OS_SIMULATOR
 128         .text
 129         .align 2,0x90
 130         .globl __dyld_start
 131 __dyld_start:
 132         popq    %rdi            # param1 = mh of app
 133         pushq   $0              # push a zero for debugger end of frames marker
 134         movq    %rsp,%rbp       # pointer to base of kernel frame
 135         andq    $-16,%rsp       # force SSE alignment
 136         subq    $16,%rsp        # room for local variables
 137
 138         # call dyldbootstrap::start(app_mh, argc, argv, dyld_mh, &startGlue)
 139         movl    8(%rbp),%esi    # param2 = argc into %esi
 140         leaq    16(%rbp),%rdx   # param3 = &argv[0] into %rdx
 141         leaq    ___dso_handle(%rip),%rcx # param4 = dyldsMachHeader into %rcx
 142         leaq    -8(%rbp),%r8    # param5 = &glue into %r8
 143         call    __ZN13dyldbootstrap5startEPKN5dyld311MachOLoadedEiPPKcS3_Pm
 144         movq    -8(%rbp),%rdi
 145         cmpq    $0,%rdi
 146         jne     Lnew
 147
 148         # clean up stack and jump to "start" in main executable
 149         movq    %rbp,%rsp       # restore the unaligned stack pointer
 150         addq    $8,%rsp         # remove the mh argument, and debugger end frame marker
 151         movq    $0,%rbp         # restore ebp back to zero
 152         jmp     *%rax           # jump to the entry point
 153
 154         # LC_MAIN case, set up stack for call to main()
 155 Lnew:   addq    $16,%rsp        # remove local variables
 156         pushq   %rdi            # simulate return address into _start in libdyld
 157         movq    8(%rbp),%rdi    # main param1 = argc into %rdi
 158         leaq    16(%rbp),%rsi   # main param2 = &argv[0] into %rsi
 159         leaq    0x8(%rsi,%rdi,8),%rdx # main param3 = &env[0] into %rdx
 160         movq    %rdx,%rcx
 161 Lapple: movq    (%rcx),%r8
 162         add     $8,%rcx
 163         testq   %r8,%r8         # look for NULL ending env[] array
 164         jne     Lapple          # main param4 = apple into %rcx
 165         jmp     *%rax           # jump to main(argc,argv,env,apple) with return address set to _start
 166 #endif /* __x86_64__ && !TARGET_OS_SIMULATOR*/
 167
 168
 169
 170 #if __arm__
 171         .text
 172         .align 2
 173 __dyld_start:
 174         mov     r8, sp          // save stack pointer
 175         sub     sp, #16         // make room for outgoing parameters
 176         bic     sp, sp, #15     // force 16-byte alignment
 177
 178         // call dyldbootstrap::start(app_mh, argc, argv, dyld_mh, &startGlue)
 179         ldr     r0, [r8]        // r0 = mach_header
 180         ldr     r1, [r8, #4]    // r1 = argc
 181         add     r2, r8, #8      // r2 = argv
 182         adr     r3, __dyld_start
 183         sub     r3 ,r3, #0x1000 // r3 = dyld_mh
 184         add     r4, sp, #12
 185         str     r4, [sp, #0]    // [sp] = &startGlue
 186
 187         bl      __ZN13dyldbootstrap5startEPKN5dyld311MachOLoadedEiPPKcS3_Pm
 188         ldr     r5, [sp, #12]
 189         cmp     r5, #0
 190         bne     Lnew
 191
 192         // traditional case, clean up stack and jump to result
 193         add     sp, r8, #4      // remove the mach_header argument.
 194         bx      r0              // jump to the program's entry point
 195
 196         // LC_MAIN case, set up stack for call to main()
 197 Lnew:   mov     lr, r5              // simulate return address into _start in libdyld
 198         mov     r5, r0              // save address of main() for later use
 199         ldr     r0, [r8, #4]        // main param1 = argc
 200         add     r1, r8, #8          // main param2 = argv
 201         add     r2, r1, r0, lsl #2
 202         add     r2, r2, #4          // main param3 = &env[0]
 203         mov     r3, r2
 204 Lapple: ldr     r4, [r3]
 205         add     r3, #4
 206         cmp     r4, #0
 207         bne     Lapple              // main param4 = apple
 208         bx      r5
 209
 210 #endif /* __arm__ */
 211
 212
 213
 214
 215 #if __arm64__ && !TARGET_OS_SIMULATOR
 216         .text
 217         .align 2
 218         .globl __dyld_start
 219 __dyld_start:
 220         mov     x28, sp
 221         and     sp, x28, #~15           // force 16-byte alignment of stack
 222         mov     x0, #0
 223         mov     x1, #0
 224         stp     x1, x0, [sp, #-16]!     // make aligned terminating frame
 225         mov     fp, sp                  // set up fp to point to terminating frame
 226         sub     sp, sp, #16             // make room for local variables
 227 #if __LP64__
 228         ldr     x0, [x28]               // get app's mh into x0
 229         ldr     x1, [x28, #8]           // get argc into x1 (kernel passes 32-bit int argc as 64-bits on stack to keep alignment)
 230         add     x2, x28, #16            // get argv into x2
 231 #else
 232         ldr     w0, [x28]               // get app's mh into x0
 233         ldr     w1, [x28, #4]           // get argc into x1 (kernel passes 32-bit int argc as 64-bits on stack to keep alignment)
 234         add     w2, w28, #8             // get argv into x2
 235 #endif
 236         adrp    x3,___dso_handle@page
 237         add     x3,x3,___dso_handle@pageoff // get dyld's mh in to x4
 238         mov     x4,sp                   // x5 has &startGlue
 239
 240         // call dyldbootstrap::start(app_mh, argc, argv, dyld_mh, &startGlue)
 241         bl      __ZN13dyldbootstrap5startEPKN5dyld311MachOLoadedEiPPKcS3_Pm
 242         mov     x16,x0                  // save entry point address in x16
 243 #if __LP64__
 244         ldr     x1, [sp]
 245 #else
 246         ldr     w1, [sp]
 247 #endif
 248         cmp     x1, #0
 249         b.ne    Lnew
 250
 251         // LC_UNIXTHREAD way, clean up stack and jump to result
 252 #if __LP64__
 253         add     sp, x28, #8             // restore unaligned stack pointer without app mh
 254 #else
 255         add     sp, x28, #4             // restore unaligned stack pointer without app mh
 256 #endif
 257 #if __arm64e__
 258         braaz   x16                     // jump to the program's entry point
 259 #else
 260         br      x16                     // jump to the program's entry point
 261 #endif
 262
 263         // LC_MAIN case, set up stack for call to main()
 264 Lnew:   mov     lr, x1              // simulate return address into _start in libdyld.dylib
 265 #if __LP64__
 266         ldr     x0, [x28, #8]       // main param1 = argc
 267         add     x1, x28, #16        // main param2 = argv
 268         add     x2, x1, x0, lsl #3
 269         add     x2, x2, #8          // main param3 = &env[0]
 270         mov     x3, x2
 271 Lapple: ldr     x4, [x3]
 272         add     x3, x3, #8
 273 #else
 274         ldr     w0, [x28, #4]       // main param1 = argc
 275         add     x1, x28, #8         // main param2 = argv
 276         add     x2, x1, x0, lsl #2
 277         add     x2, x2, #4          // main param3 = &env[0]
 278         mov     x3, x2
 279 Lapple: ldr     w4, [x3]
 280         add     x3, x3, #4
 281 #endif
 282         cmp     x4, #0
 283         b.ne    Lapple              // main param4 = apple
 284 #if __arm64e__
 285         braaz   x16
 286 #else
 287         br      x16
 288 #endif
 289
 290 #endif // __arm64__ && !TARGET_OS_SIMULATOR
 291
 292
 293 // When iOS 10.0 simulator runs on 10.11, abort_with_payload() does not exist,
 294 // so it falls back and uses dyld_fatal_error().
 295 #if TARGET_OS_SIMULATOR
 296         .text
 297         .align 2
 298         .globl  _dyld_fatal_error
 299 _dyld_fatal_error:
 300 #if __arm64__ || __arm64e__
 301     brk #3
 302 #else
 303     int3
 304 #endif
 305     nop
 306 #endif
 307