| /* Machine-dependent ELF startup code. PowerPC version. |
| Copyright (C) 1995-2000, 2002, 2004, 2005, 2006 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. |
| |
| 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, write to the Free |
| Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA |
| 02110-1301 USA. */ |
| |
| #include <sysdep.h> |
| |
| /* Initial entry point code for the dynamic linker. |
| The C function `_dl_start' is the real entry point; |
| its return value is the user program's entry point. */ |
| ENTRY(_start) |
| /* We start with the following on the stack, from top: |
| argc (4 bytes); |
| arguments for program (terminated by NULL); |
| environment variables (terminated by NULL); |
| arguments for the program loader. */ |
| |
| /* Call _dl_start with one parameter pointing at argc */ |
| mr r3,r1 |
| /* (we have to frob the stack pointer a bit to allow room for |
| _dl_start to save the link register). */ |
| li r4,0 |
| addi r1,r1,-16 |
| stw r4,0(r1) |
| bl _dl_start@local |
| |
| /* FALLTHRU */ |
| _dl_start_user: |
| /* Now, we do our main work of calling initialisation procedures. |
| The ELF ABI doesn't say anything about parameters for these, |
| so we just pass argc, argv, and the environment. |
| Changing these is strongly discouraged (not least because argc is |
| passed by value!). */ |
| |
| /* Put our GOT pointer in r31, */ |
| bcl 20,31,1f |
| 1: mflr r31 |
| addis r31,r31,_GLOBAL_OFFSET_TABLE_-1b@ha |
| addi r31,r31,_GLOBAL_OFFSET_TABLE_-1b@l |
| /* the address of _start in r30, */ |
| mr r30,r3 |
| /* &_dl_argc in 29, &_dl_argv in 27, and _dl_loaded in 28. */ |
| lwz r28,_rtld_global@got(r31) |
| lwz r29,_dl_argc@got(r31) |
| lwz r27,_dl_argv@got(r31) |
| |
| /* Call _dl_init (_dl_loaded, _dl_argc, _dl_argv, _dl_argv+_dl_argc+1). */ |
| lwz r3,0(r28) |
| lwz r4,0(r29) |
| lwz r5,0(r27) |
| slwi r6,r4,2 |
| add r6,r5,r6 |
| addi r6,r6,4 |
| bl _dl_init_internal@local |
| |
| /* Now, to conform to the ELF ABI, we have to: */ |
| /* Pass argc (actually _dl_argc) in r3; */ |
| lwz r3,0(r29) |
| /* pass argv (actually _dl_argv) in r4; */ |
| lwz r4,0(r27) |
| /* pass envp (actually _dl_argv+_dl_argc+1) in r5; */ |
| slwi r5,r3,2 |
| add r6,r4,r5 |
| addi r5,r6,4 |
| /* pass the auxilary vector in r6. This is passed to us just after _envp. */ |
| 2: lwzu r0,4(r6) |
| cmpwi r0,0 |
| bne 2b |
| addi r6,r6,4 |
| /* Pass a termination function pointer (in this case _dl_fini) in r7. */ |
| lwz r7,_dl_fini@got(r31) |
| /* Now, call the start function in r30... */ |
| mtctr r30 |
| /* Pass the stack pointer in r1 (so far so good), pointing to a NULL value. |
| (This lets our startup code distinguish between a program linked statically, |
| which linux will call with argc on top of the stack which will hopefully |
| never be zero, and a dynamically linked program which will always have |
| a NULL on the top of the stack). |
| Take the opportunity to clear LR, so anyone who accidentally returns |
| from _start gets SEGV. Also clear the next few words of the stack. */ |
| |
| _dl_main_dispatch: |
| li r31,0 |
| stw r31,0(r1) |
| mtlr r31 |
| stw r31,4(r1) |
| stw r31,8(r1) |
| stw r31,12(r1) |
| /* Go do it! */ |
| bctr |
| END(_start) |
