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- /* Startup code for ARM & ELF
- Copyright (C) 1995, 1996, 1997, 1998, 2001, 2002, 2005
- Free Software Foundation, Inc.
- This file is part of the GNU C Library.
- The GNU C Library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public
- License as published by the Free Software Foundation; either
- version 2.1 of the License, or (at your option) any later version.
- In addition to the permissions in the GNU Lesser General Public
- License, the Free Software Foundation gives you unlimited
- permission to link the compiled version of this file with other
- programs, and to distribute those programs without any restriction
- coming from the use of this file. (The GNU Lesser General Public
- License restrictions do apply in other respects; for example, they
- cover modification of the file, and distribution when not linked
- into another program.)
- Note that people who make modified versions of this file are not
- obligated to grant this special exception for their modified
- versions; it is their choice whether to do so. The GNU Lesser
- General Public License gives permission to release a modified
- version without this exception; this exception also makes it
- possible to release a modified version which carries forward this
- exception.
- The GNU C Library is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
- You should have received a copy of the GNU Lesser General Public
- License along with the GNU C Library; if not, see
- <http://www.gnu.org/licenses/>. */
- /* This is the canonical entry point, usually the first thing in the text
- segment.
- Note that the code in the .init section has already been run.
- This includes _init and _libc_init
- At this entry point, most registers' values are unspecified, except:
- a1 Contains a function pointer to be registered with `atexit'.
- This is how the dynamic linker arranges to have DT_FINI
- functions called for shared libraries that have been loaded
- before this code runs.
- sp The stack contains the arguments and environment:
- 0(sp) argc
- 4(sp) argv[0]
- ...
- (4*argc)(sp) NULL
- (4*(argc+1))(sp) envp[0]
- ...
- NULL
- */
- /*
- For uClinux it looks like this:
- argc argument counter (integer)
- argv char *argv[]
- envp char *envp[]
- argv[0] program name (pointer)
- argv[1...N] program args (pointers)
- argv[argc-1] end of args (integer)
- NULL
- env[0...N] environment variables (pointers)
- NULL
- ARM register quick reference:
- Name Number ARM Procedure Calling Standard Role
- a1 r0 argument 1 / integer result / scratch register / argc
- a2 r1 argument 2 / scratch register / argv
- a3 r2 argument 3 / scratch register / envp
- a4 r3 argument 4 / scratch register
- v1 r4 register variable
- v2 r5 register variable
- v3 r6 register variable
- v4 r7 register variable
- v5 r8 register variable
- sb/v6 r9 static base / register variable
- sl/v7 r10 stack limit / stack chunk handle / reg. variable
- fp r11 frame pointer
- ip r12 scratch register / new-sb in inter-link-unit calls
- sp r13 lower end of current stack frame
- lr r14 link address / scratch register
- pc r15 program counter
- */
- #include <features.h>
- #include <bits/arm_asm.h>
- #if defined(__FDPIC__)
- .text
- .arm
- .globl _start
- _start:
- /* Start by self relocation. */
- sub r4, pc, #8
- ldr r1, .L__ROFIXUP_LIST__
- add r1, r1, r4
- ldr r2, .L__ROFIXUP_END__
- add r2, r2, r4
- mov r0, r7
- push {r9, r10}
- bl __self_reloc
- pop {r9, r10}
- mov r9, r0
- /* Clear the frame pointer since this is the outermost frame. */
- mov r3, #0
- mov fp, r3
- /* Now fill __uClibc_main arguments. */
- sub sp, sp, #16 /* Reserve space for 3 args (keep aligment) */
- ldr r0, .L_main_got_funcdesc /* r0 GOT FUNCDESC of main */
- ldr r0, [r9, r0]
- ldr r1, [sp, #16] /* argc */
- add r2, sp, #20 /* argv */
- ldr r3, .L_init_got_funcdesc /* r3 GOT init */
- ldr r3, [r9, r3]
- ldr r4, .L_fini_got_funcdesc
- ldr r4, [r9, r4]
- str r4, [sp, #0] /* sp + 0 GOT fini */
- movs r4, r8 /* Test if static binary (r8 is 0 as there is no interpreter). */
- movne r4, r10
- moveq r4, #0
- str r4, [sp, #4] /* sp + 4 got rtld_fini */
- mov r4, r2 /* stack_end is unused.... */
- str r4, [sp, #8] /* sp + 8 got stack_end */
- bl __uClibc_main
- /* We should never get here.... */
- bl abort
- .L__ROFIXUP_LIST__:
- .word __ROFIXUP_LIST__ - _start
- .L__ROFIXUP_END__:
- .word __ROFIXUP_END__ - _start
- .L_main_got_funcdesc:
- .word main(GOTFUNCDESC)
- .L_init_got_funcdesc:
- .word _init(GOTFUNCDESC)
- .L_fini_got_funcdesc:
- .word _fini(GOTFUNCDESC)
- /* Define a symbol for the first piece of initialized data. */
- .data
- .globl __data_start
- __data_start:
- .long 0
- .weak data_start
- data_start = __data_start
- #else /* defined(__FDPIC__) */
- .text
- .globl _start
- .type _start,%function
- .type _init,%function
- .type _fini,%function
- #ifndef __UCLIBC_CTOR_DTOR__
- .weak _init
- .weak _fini
- #endif
- #if defined(THUMB1_ONLY)
- .thumb_func
- _start:
- /* Clear the frame pointer since this is the outermost frame. */
- mov r3, #0
- mov fp, r3
- #ifdef __ARCH_USE_MMU__
- /* Pop argc off the stack and save a pointer to argv */
- pop {a2}
- mov a3, sp
- #else
- /*
- * uClinux/arm stacks look a little different from normal
- * MMU-full Linux/arm stacks (for no good reason)
- */
- /* pull argc and argv off the stack. We are going to push 3
- * arguments, so pop one here to maintain doubleword alignment. */
- pop {a2}
- ldr a3, [sp]
- #endif
- /* Push stack limit and rtld_fini */
- push {a1, a3}
- #ifdef __PIC__
- ldr r4, .L_GOT
- adr r5, .L_GOT
- add r4, r5, r4
- ldr r5, .L_GOT+4 /* _fini */
- ldr a1, [r4, r5]
- push {a1} /* Push _fini */
- ldr r5, .L_GOT+8 /* _init */
- ldr a4, [r4, r5]
-
- ldr r5, .L_GOT+12 /* main */
- ldr a1, [r4, r5]
- #else
- /* Fetch address of fini */
- ldr r4, =_fini
- /* Push fini */
- push {r4}
- /* Set up the other arguments in registers */
- ldr a1, =main
- ldr a4, =_init
- #endif
- /* __uClibc_main (main, argc, argv, init, fini, rtld_fini, stack_end) */
- /* Let the libc call main and exit with its return code. */
- bl __uClibc_main
- /* should never get here....*/
- bl abort
- .pool
- #ifdef __PIC__
- .L_GOT:
- .word _GLOBAL_OFFSET_TABLE_-.L_GOT
- .word _fini(GOT)
- .word _init(GOT)
- .word main(GOT)
- #endif
- #else /* !THUMB1_ONLY */
- _start:
- /* Clear the frame pointer and link register since this is the outermost frame. */
- mov fp, #0
- mov lr, #0
- #ifdef __ARCH_USE_MMU__
- /* Pop argc off the stack and save a pointer to argv */
- ldr a2, [sp], #4
- mov a3, sp
- #else
- /*
- * uClinux/arm stacks look a little different from normal
- * MMU-full Linux/arm stacks (for no good reason)
- */
- /* pull argc and argv off the stack. We are going to push 3
- * arguments, so pop one here to maintain doubleword alignment. */
- ldr a2, [sp], #4
- ldr a3, [sp]
- #endif
- /* Push stack limit */
- str a3, [sp, #-4]!
- /* Push rtld_fini */
- str a1, [sp, #-4]!
- #ifdef __PIC__
- ldr sl, .L_GOT
- adr a4, .L_GOT
- add sl, sl, a4
- ldr ip, .L_GOT+4 /* _fini */
- ldr a1, [sl, ip]
- str a1, [sp, #-4]! /* Push _fini */
- ldr ip, .L_GOT+8 /* _init */
- ldr a4, [sl, ip]
-
- ldr ip, .L_GOT+12 /* main */
- ldr a1, [sl, ip]
- /* __uClibc_main (main, argc, argv, init, fini, rtld_fini, stack_end) */
- /* Let the libc call main and exit with its return code. */
- b __uClibc_main(PLT)
- #else
- /* Fetch address of fini */
- ldr ip, =_fini
- /* Push fini */
- str ip, [sp, #-4]!
- /* Set up the other arguments in registers */
- ldr a1, =main
- ldr a4, =_init
- /* __uClibc_main (main, argc, argv, init, fini, rtld_fini, stack_end) */
- /* Let the libc call main and exit with its return code. */
- b __uClibc_main
- #endif
- /* should never get here....*/
- bl abort
- #ifdef __PIC__
- .L_GOT:
- .word _GLOBAL_OFFSET_TABLE_ - .L_GOT
- .word _fini(GOT)
- .word _init(GOT)
- .word main(GOT)
- #endif
- #endif
- /* Define a symbol for the first piece of initialized data. */
- .data
- .globl __data_start
- __data_start:
- .long 0
- .weak data_start
- data_start = __data_start
- #endif /* defined(__FDPIC__) */
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