diff options
Diffstat (limited to 'sysdeps/mips/elf')
| -rw-r--r-- | sysdeps/mips/elf/start.S | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/sysdeps/mips/elf/start.S b/sysdeps/mips/elf/start.S new file mode 100644 index 0000000000..0db3a04a7d --- /dev/null +++ b/sysdeps/mips/elf/start.S @@ -0,0 +1,181 @@ +/* Startup code compliant to the ELF Mips ABI. +Copyright (C) 1995 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 Library General Public License as +published by the Free Software Foundation; either version 2 of the +License, or (at your option) any later version. + +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 +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 675 Mass Ave, +Cambridge, MA 02139, USA. */ + +/* This is the canonical entry point, usually the first thing in the text + segment. The SVR4/Mips ABI (pages 3-31, 3-32) says that when the entry + point runs, most registers' values are unspecified, except for: + + v1 ($2) 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 ($29) The stack contains the arguments and environment: + 0(%esp) argc + 4(%esp) argv[0] + ... + (4*argc)(%esp) NULL + (4*(argc+1))(%esp) envp[0] + ... + NULL + ra ($31) The return address register is set to zero so that programs + that search backword through stack frames recognize the last + stack frame. +*/ + +#ifdef PIC +/* A macro to (re)initialize gp. We can get the run time address of 0f in + ra ($31) by blezal instruction. In this early phase, we can't save gp + in stack and .cprestore doesn't work properly. So we set gp by using + this macro. */ +#define SET_GP \ + .set noreorder; \ + bltzal $0,0f; \ + nop; \ +0: .cpload $31; \ + .set reorder; +#endif + + .text + .globl _start +_start: +#ifdef PIC + SET_GP +#endif + move $31, $0 + + /* $2 contains the address of the shared library termination + function, which we will register with `atexit' to be called by + `exit'. I suspect that on some systems, and when statically + linked, this will not be set by anything to any function + pointer; hopefully it will be zero so we don't try to call + random pointers. */ + beq $2, $0, nofini + move $4, $2 + jal atexit +#ifdef PIC + SET_GP +#endif +nofini: + + /* Do essential libc initialization. In statically linked + programs under the GNU Hurd, this is what sets up the + arguments on the stack for the code below. Since the argument + registers (a0 - a3) saved to the first 4 stack entries by + the prologue of __libc_init_first, we preload them to + prevent clobbering the stack tops. In Hurd case, stack pointer + ($29) may be VM_MAX_ADDRESS here. If so, we must modify it. */ +#if (__mips64) + dli $4, 0x10000000000 + bne $29, $4, 1f + dsubu $29, 32 + sd $0, 0($29) + sd $0, 8($29) + sd $0, 16($29) + sd $0, 24($29) +1: + ld $4, 0($29) + ld $5, 8($29) + ld $6, 16($29) + ld $7, 24($29) +#else /* __mips64 */ + li $4, 0x80000000 + bne $29, $4, 1f + subu $29, 16 + sw $0, 0($29) + sw $0, 4($29) + sw $0, 8($29) + sw $0, 12($29) +1: + lw $4, 0($29) + lw $5, 4($29) + lw $6, 8($29) + lw $7, 12($29) +#endif /* __mips64 */ + + jal __libc_init_first +#ifdef PIC + SET_GP +#endif +#if (__mips64) + ld $4, 0($29) + ld $5, 8($29) + ld $6, 16($29) + ld $7, 24($29) +#else /* __mips64 */ + lw $4, 0($29) + lw $5, 4($29) + lw $6, 8($29) + lw $7, 12($29) +#endif /* __mips64 */ + + /* Call `_init', which is the entry point to our own `.init' + section; and register with `atexit' to have `exit' call + `_fini', which is the entry point to our own `.fini' section. */ + jal _init +#ifdef PIC + SET_GP +#endif +#if (__mips64) + dla $4, _fini +#else /* __mips64 */ + la $4, _fini +#endif /* __mips64 */ + + jal atexit +#ifdef PIC + SET_GP +#endif + + /* Extract the arguments and environment as encoded on the stack + and set up the arguments for `main': argc, argv, envp. */ +#if (__mips64) + ld $4, 0($29) /* argc */ + daddu $5, $29, 8 /* argv */ + dsll $6, $4, 3 + daddu $6, $6, 8 + daddu $6, $5, $6 /* envp = &argv[argc + 1] */ +#else /* __mips64 */ + lw $4, 0($29) /* argc */ + addu $5, $29, 4 /* argv */ + sll $6, $4, 2 + addu $6, $6, 4 + addu $6, $5, $6 /* envp = &argv[argc + 1] */ +#endif /* __mips64 */ + + /* Call the user's main function, and exit with its value. */ + jal main +#ifdef PIC + SET_GP +#endif + move $4, $2 + jal exit /* This should never return. */ +hlt: b hlt /* Crash if somehow it does return. */ + +/* Define a symbol for the first piece of initialized data. */ + .data + .globl __data_start +__data_start: +#if (__mips64) + .dword 0 +#else /* __mips64 */ + .word 0 +#endif /* __mips64 */ + .weak data_start + data_start = __data_start |