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 #ifdef __i386__
  72
  73 #if !TARGET_IPHONE_SIMULATOR
  74         .text
  75         .align  4, 0x90
  76         .globl __dyld_start
  77 __dyld_start:
  78         popl    %edx            # edx = mh of app
  79         pushl   $0              # push a zero for debugger end of frames marker
  80         movl    %esp,%ebp       # pointer to base of kernel frame
  81         andl    $-16,%esp       # force SSE alignment
  82         subl    $32,%esp        # room for locals and outgoing parameters
  83
  84         call    L__dyld_start_picbase
  85 L__dyld_start_picbase:
  86         popl    %ebx            # set %ebx to runtime value of picbase
  87
  88         movl    Lmh-L__dyld_start_picbase(%ebx), %ecx # ecx = prefered load address
  89         movl    __dyld_start_static_picbase-L__dyld_start_picbase(%ebx), %eax
  90         subl    %eax, %ebx      # ebx = slide = L__dyld_start_picbase - [__dyld_start_static_picbase]
  91         addl    %ebx, %ecx      # ecx = actual load address
  92         # call dyldbootstrap::start(app_mh, argc, argv, slide, dyld_mh, &startGlue)
  93         movl    %edx,(%esp)     # param1 = app_mh
  94         movl    4(%ebp),%eax
  95         movl    %eax,4(%esp)    # param2 = argc
  96         lea     8(%ebp),%eax
  97         movl    %eax,8(%esp)    # param3 = argv
  98         movl    %ebx,12(%esp)   # param4 = slide
  99         movl    %ecx,16(%esp)   # param5 = actual load address
 100         lea     28(%esp),%eax
 101         movl    %eax,20(%esp)   # param6 = &startGlue
 102         call    __ZN13dyldbootstrap5startEPK12macho_headeriPPKclS2_Pm
 103         movl    28(%esp),%edx
 104         cmpl    $0,%edx
 105         jne     Lnew
 106
 107         # clean up stack and jump to "start" in main executable
 108         movl    %ebp,%esp       # restore the unaligned stack pointer
 109         addl    $4,%esp         # remove debugger end frame marker
 110         movl    $0,%ebp         # restore ebp back to zero
 111         jmp     *%eax           # jump to the entry point
 112
 113         # LC_MAIN case, set up stack for call to main()
 114 Lnew:   movl    4(%ebp),%ebx
 115         movl    %ebx,(%esp)     # main param1 = argc
 116         leal    8(%ebp),%ecx
 117         movl    %ecx,4(%esp)    # main param2 = argv
 118         leal    0x4(%ecx,%ebx,4),%ebx
 119         movl    %ebx,8(%esp)    # main param3 = env
 120 Lapple: movl    (%ebx),%ecx     # look for NULL ending env[] array
 121         add     $4,%ebx
 122         testl   %ecx,%ecx
 123         jne     Lapple          # once found, next pointer is "apple" parameter now in %ebx
 124         movl    %ebx,12(%esp)   # main param4 = apple
 125         pushl   %edx            # simulate return address into _start in libdyld
 126         jmp     *%eax           # jump to main(argc,argv,env,apple) with return address set to _start
 127 #endif
 128
 129 #if !TARGET_IPHONE_SIMULATOR
 130         .data
 131 __dyld_start_static_picbase:
 132         .long   L__dyld_start_picbase
 133 Lmh:    .long   ___dso_handle
 134 #endif
 135
 136
 137 #endif /* __i386__ */
 138
 139
 140
 141 #if __x86_64__
 142 #if !TARGET_IPHONE_SIMULATOR
 143         .data
 144         .align 3
 145 __dyld_start_static:
 146         .quad   __dyld_start
 147 #endif
 148
 149
 150 #if !TARGET_IPHONE_SIMULATOR
 151         .text
 152         .align 2,0x90
 153         .globl __dyld_start
 154 __dyld_start:
 155         popq    %rdi            # param1 = mh of app
 156         pushq   $0              # push a zero for debugger end of frames marker
 157         movq    %rsp,%rbp       # pointer to base of kernel frame
 158         andq    $-16,%rsp       # force SSE alignment
 159         subq    $16,%rsp        # room for local variables
 160
 161         # call dyldbootstrap::start(app_mh, argc, argv, slide, dyld_mh, &startGlue)
 162         movl    8(%rbp),%esi    # param2 = argc into %esi
 163         leaq    16(%rbp),%rdx   # param3 = &argv[0] into %rdx
 164         movq    __dyld_start_static(%rip), %r8
 165         leaq    __dyld_start(%rip), %rcx
 166         subq     %r8, %rcx      # param4 = slide into %rcx
 167         leaq    ___dso_handle(%rip),%r8 # param5 = dyldsMachHeader
 168         leaq    -8(%rbp),%r9
 169         call    __ZN13dyldbootstrap5startEPK12macho_headeriPPKclS2_Pm
 170         movq    -8(%rbp),%rdi
 171         cmpq    $0,%rdi
 172         jne     Lnew
 173
 174         # clean up stack and jump to "start" in main executable
 175         movq    %rbp,%rsp       # restore the unaligned stack pointer
 176         addq    $8,%rsp         # remove the mh argument, and debugger end frame marker
 177         movq    $0,%rbp         # restore ebp back to zero
 178         jmp     *%rax           # jump to the entry point
 179
 180         # LC_MAIN case, set up stack for call to main()
 181 Lnew:   addq    $16,%rsp        # remove local variables
 182         pushq   %rdi            # simulate return address into _start in libdyld
 183         movq    8(%rbp),%rdi    # main param1 = argc into %rdi
 184         leaq    16(%rbp),%rsi   # main param2 = &argv[0] into %rsi
 185         leaq    0x8(%rsi,%rdi,8),%rdx # main param3 = &env[0] into %rdx
 186         movq    %rdx,%rcx
 187 Lapple: movq    (%rcx),%r8
 188         add     $8,%rcx
 189         testq   %r8,%r8         # look for NULL ending env[] array
 190         jne     Lapple          # main param4 = apple into %rcx
 191         jmp     *%rax           # jump to main(argc,argv,env,apple) with return address set to _start
 192
 193 #endif /* TARGET_IPHONE_SIMULATOR */
 194 #endif /* __x86_64__ */
 195
 196
 197
 198 #if __arm__
 199         .syntax unified
 200         .data
 201         .align 2
 202 __dyld_start_static_picbase:
 203         .long   L__dyld_start_picbase
 204
 205
 206         // Hack to make ___dso_handle work
 207         // Without this local symbol, assembler will error out about in subtraction expression
 208         // The real ___dso_handle (non-weak) sythesized by the linker
 209         // Since this one is weak, the linker will throw this one away and use the real one instead.
 210         .data
 211         .globl ___dso_handle
 212         .weak_definition ___dso_handle
 213 ___dso_handle:  .long 0
 214
 215         .text
 216         .align 2
 217 __dyld_start:
 218         mov     r8, sp          // save stack pointer
 219         sub     sp, #16         // make room for outgoing parameters
 220         bic     sp, sp, #15     // force 16-byte alignment
 221
 222         // call dyldbootstrap::start(app_mh, argc, argv, slide, dyld_mh, &startGlue)
 223
 224         ldr     r3, L__dyld_start_picbase_ptr
 225 L__dyld_start_picbase:
 226         sub     r0, pc, #8      // load actual PC
 227         ldr     r3, [r0, r3]    // load expected PC
 228         sub     r3, r0, r3      // r3 = slide
 229
 230         ldr     r0, [r8]        // r0 = mach_header
 231         ldr     r1, [r8, #4]    // r1 = argc
 232         add     r2, r8, #8      // r2 = argv
 233
 234         ldr     r4, Lmh
 235 L3:     add     r4, r4, pc
 236         str     r4, [sp, #0]    // [sp] = dyld_mh
 237         add     r4, sp, #12
 238         str     r4, [sp, #4]    // [sp+4] = &startGlue
 239
 240         bl      __ZN13dyldbootstrap5startEPK12macho_headeriPPKclS2_Pm
 241         ldr     r5, [sp, #12]
 242         cmp     r5, #0
 243         bne     Lnew
 244
 245         // traditional case, clean up stack and jump to result
 246         add     sp, r8, #4      // remove the mach_header argument.
 247         bx      r0              // jump to the program's entry point
 248
 249         // LC_MAIN case, set up stack for call to main()
 250 Lnew:   mov     lr, r5              // simulate return address into _start in libdyld
 251         mov     r5, r0              // save address of main() for later use
 252         ldr     r0, [r8, #4]        // main param1 = argc
 253         add     r1, r8, #8          // main param2 = argv
 254         add     r2, r1, r0, lsl #2
 255         add     r2, r2, #4          // main param3 = &env[0]
 256         mov     r3, r2
 257 Lapple: ldr     r4, [r3]
 258         add     r3, #4
 259         cmp     r4, #0
 260         bne     Lapple              // main param4 = apple
 261         bx      r5
 262
 263         .align 2
 264 L__dyld_start_picbase_ptr:
 265         .long   __dyld_start_static_picbase-L__dyld_start_picbase
 266 Lmh:    .long   ___dso_handle-L3-8
 267
 268 #endif /* __arm__ */
 269
 270
 271
 272
 273 #if __arm64__
 274         .data
 275         .align 3
 276 __dso_static:
 277         .quad   ___dso_handle
 278
 279         .text
 280         .align 2
 281         .globl __dyld_start
 282 __dyld_start:
 283         mov     x28, sp
 284         and     sp, x28, #~15           // force 16-byte alignment of stack
 285         mov     x0, #0
 286         mov     x1, #0
 287         stp     x1, x0, [sp, #-16]!     // make aligned terminating frame
 288         mov     fp, sp                  // set up fp to point to terminating frame
 289         sub     sp, sp, #16             // make room for local variables
 290         ldr     x0, [x28]               // get app's mh into x0
 291         ldr     x1, [x28, #8]           // get argc into x1 (kernel passes 32-bit int argc as 64-bits on stack to keep alignment)
 292         add     x2, x28, #16            // get argv into x2
 293         adrp    x4,___dso_handle@page
 294         add     x4,x4,___dso_handle@pageoff // get dyld's mh in to x4
 295         adrp    x3,__dso_static@page
 296         ldr     x3,[x3,__dso_static@pageoff] // get unslid start of dyld
 297         sub     x3,x4,x3                // x3 now has slide of dyld
 298         mov     x5,sp                   // x5 has &startGlue
 299
 300         // call dyldbootstrap::start(app_mh, argc, argv, slide, dyld_mh, &startGlue)
 301         bl      __ZN13dyldbootstrap5startEPK12macho_headeriPPKclS2_Pm
 302         mov     x16,x0                  // save entry point address in x16
 303         ldr     x1, [sp]
 304         cmp     x1, #0
 305         b.ne    Lnew
 306
 307         // LC_UNIXTHREAD way, clean up stack and jump to result
 308         add     sp, x28, #8             // restore unaligned stack pointer without app mh
 309         br      x16                     // jump to the program's entry point
 310
 311         // LC_MAIN case, set up stack for call to main()
 312 Lnew:   mov     lr, x1              // simulate return address into _start in libdyld.dylib
 313         ldr     x0, [x28, #8]       // main param1 = argc
 314         add     x1, x28, #16        // main param2 = argv
 315         add     x2, x1, x0, lsl #3
 316         add     x2, x2, #8          // main param3 = &env[0]
 317         mov     x3, x2
 318 Lapple: ldr     x4, [x3]
 319         add     x3, x3, #8
 320         cmp     x4, #0
 321         b.ne    Lapple              // main param4 = apple
 322         br      x16
 323
 324 #endif // __arm64__
 325
 326
 327 // When iOS 10.0 simulator runs on 10.11, abort_with_payload() does not exist,
 328 // so it falls back and uses dyld_fatal_error().
 329 #if TARGET_IPHONE_SIMULATOR
 330         .text
 331         .align 2
 332         .globl  _dyld_fatal_error
 333 _dyld_fatal_error:
 334     int3
 335     nop
 336 #endif
 337
 338
 339
 340
 341