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m0skit0
Joined: 02 Jun 2009
Posts: 226
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 Posted: Thu Jul 16, 2009 1:07 am Post subject: About _init and _start |
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Just a quick question: _init is for data intialization and it is executed before _start... is this right? Because ELF header sets entry point for _start address.
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| The Incredible Bill Gates wrote: | | The obvious mathematical breakthrough would be development of an easy way to factor large prime numbers. |
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TyRaNiD
Joined: 18 Jan 2004
Posts: 918
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| Posted: Thu Jul 16, 2009 3:29 am Post subject: |
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| As long as _start is set to the entry point it runs before _init, well in actual fact your _start routine is responsible for calling _init |
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m0skit0
Joined: 02 Jun 2009
Posts: 226
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| Posted: Thu Jul 16, 2009 4:42 am Post subject: |
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Arigato sensei :)
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| The Incredible Bill Gates wrote: | | The obvious mathematical breakthrough would be development of an easy way to factor large prime numbers. |
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sauron_le_noir
Joined: 05 Jul 2008
Posts: 229
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| Posted: Thu Jul 16, 2009 10:25 am Post subject: |
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tyranid what is the difference between module_start and _start ?
does the function module_start call _start ? |
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TyRaNiD
Joined: 18 Jan 2004
Posts: 918
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| Posted: Thu Jul 16, 2009 3:21 pm Post subject: |
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| There is no difference, module_start is just a synonym for _start. The reason you will see module_start being used is that the actual name sony used (based on reversing the hash) and so in certain situations we use that name for ease. |
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sauron_le_noir
Joined: 05 Jul 2008
Posts: 229
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| Posted: Thu Jul 16, 2009 9:55 pm Post subject: |
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when i don"t declare _start and declare module_start the linker complain about _start missing.
| Code: |
.globl module_info
.section .rodata.sceModuleInfo,"a",@progbits
.align 4
.type module_info, @object
.size module_info, 52
module_info:
.half 0
.byte 1
.byte 1
.ascii "Hello world\000"
.space 15
.byte 0
.word _gp
.word __lib_ent_top
.word __lib_ent_bottom
.word __lib_stub_top
.word __lib_stub_bottom
.set push
.section .lib.ent.top, "a", @progbits
.align 2
.word 0
__lib_ent_top:
.section .lib.ent.btm, "a", @progbits
.align 2
__lib_ent_bottom:
.word 0
.section .lib.stub.top, "a", @progbits
.align 2
.word 0
__lib_stub_top:
.section .lib.stub.btm, "a", @progbits
.align 2
__lib_stub_bottom:
.word 0
IMPORT_START "LoadExecForKernel",0x00010000
IMPORT_FUNC "LoadExecForKernel",0x05572A5F,sceKernelExitGame
.set pop
.text
.rdata
.align 2
$LC2:
.ascii "Hello World from ASM Mips!\000"
.align 2
.globl module_start
.set nomips16
.text
_start:
module_start:
.set noreorder
addiu $sp,$sp,-8
sw $31,4($sp)
sw $fp,0($sp)
move $fp,$sp
# jal pspDebugScreenInit
# nop
lui $2,%hi($LC2)
addiu $4,$2,%lo($LC2)
# jal pspDebugScreenPrintf
# nop
jal sceKernelExitGame
nop
move $2,$0
move $sp,$fp
lw $31,4($sp)
lw $fp,0($sp)
addiu $sp,$sp,8
j $31
nop
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sp-gcc -I. -I/home/f731/pspdev/psp/sdk/include -O2 -G0 -Wall -mno-crt0 -nostartfiles -I. -I/home/f731/pspdev/psp/sdk/include -O2 -G0 -Wall -mno-crt0 -nostartfiles -o helloworld.o helloworld.s
/home/f731/pspdev/lib/gcc/psp/4.3.2/../../../../psp/bin/ld: AVERTISSEMENT: ne peut trouver le symbole d'entrée _start; utilise par défaut 0000000008900018
i try to make a hello world program in asm mips for kernel 3.x
when i add .globl _start the warning dissaspear |
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J.F.
Joined: 22 Feb 2004
Posts: 2906
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| Posted: Fri Jul 17, 2009 1:52 am Post subject: |
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| Add -S to the CFLAGS in the makefile and make one of the simple examples that come with the SDK. That will generate assembly files for everything. That's the best way to figure all that out. |
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sauron_le_noir
Joined: 05 Jul 2008
Posts: 229
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| Posted: Fri Jul 17, 2009 5:56 am Post subject: |
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Done JF thx a lot. I was studying mips assembler with a emulator called
yams. But there was a lot of pseudo code generated that are elf related and not
mips related like progbits etc ...(thx m0skit0 for the explantion)
The purpose was just to make a hello world in asm working on the psp on en 3.x firmware.
nb: I was obliged to add the -c so the linkedit is not performed and the .S file
is not deleted but if you do that you must also see at the source of the crt0.s
of the sdk to have a working sample ;)
psp-gcc -I/home/f731/pspdev/psp/sdk/include -O2 -G0 -Wall -c -S main.c |
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J.F.
Joined: 22 Feb 2004
Posts: 2906
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| Posted: Fri Jul 17, 2009 8:40 am Post subject: |
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| Oh, yeah - I keep forgetting you need to put those two switches together. :) |
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TyRaNiD
Joined: 18 Jan 2004
Posts: 918
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| Posted: Sat Jul 18, 2009 3:32 am Post subject: |
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| When building a program as an ELF it uses _start (for legacy reasons) when building a prx it uses module_start (for crazy reasons) |
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