diff options
Diffstat (limited to 'sysdeps/powerpc/powerpc32/dl-start.S')
| -rw-r--r-- | sysdeps/powerpc/powerpc32/dl-start.S | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/sysdeps/powerpc/powerpc32/dl-start.S b/sysdeps/powerpc/powerpc32/dl-start.S new file mode 100644 index 0000000000..527982bfdf --- /dev/null +++ b/sysdeps/powerpc/powerpc32/dl-start.S @@ -0,0 +1,105 @@ +/* Machine-dependent ELF startup code. PowerPC version. + Copyright (C) 1995-2000, 2002 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., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 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 */ +ENTRY(_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, */ + bl _GLOBAL_OFFSET_TABLE_-4@local + mflr r31 +/* 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 + lwz r26,_dl_starting_up@got(r31) +/* 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. */ + + li r31,0 + stw r31,0(r1) + mtlr r31 + stw r31,4(r1) + stw r31,8(r1) + stw r31,12(r1) +/* Clear _dl_starting_up. */ + stw r31,0(r26) +/* Go do it! */ + bctr +END(_start) |