Many many thanx for your help. Because of your help, i have been able to do the following.
1. Write an assembly program for octeon which starts with a routine __start.
2. Extend this program such that it calls a function written in C which resides in another file compiled separately but linked statically to make one executable.
Essentialy i use following sequence of commands for compilation and linking
$as hello2.s -o hello2.o
$gcc -c c_func.c -o c_func.o
$gcc -O2 -g -Wall -Wmissing-prototypes -Wshadow -Wpointer-arith -Wstrict-prototypes -Wmissing-declarations -Wno-format-zero-length -fno-strict-aliasing -Wno-long-long -Wno-pointer-sign -Wdeclaration-after-statement -fno-stack-protector -static -Wl,-defsym,valt_load_address=0x40000000 -nodefaultlibs -nostartfiles -u start -Wl,-T,valt_load_address_mips64_linux.lds -o hello2 hello2.o c_func.o -lgcc
All this is great but i need to do a bit more. I have to write a c program which has entry point __start written in inline-assembly and makes use of c functions (and global data ) defined in same file. I wrote a program for this purpose and tried to compile and link it using different methods but it did not work. The program compiles but gives a segmentation fault. Below is the code for the program.
The code of hello_in_c.c
-----------------------------------
int f1()
{
//called
return 0;
}
asm(
".text\n"
".globl __start\n"
".ent __start \n"
"__start: \n"
"\t.set noreorder \n"
"\t.cpload $gp\n"
"\t.set reorder\n"
"\tli $4, 1\n"
"\tla $5, stradr \n"
"\tlw $6, strlen\n"
"\tli $2, 4004\n"
"\tsyscall\n"
"\tjal f1\n"
"\tmove $4, $0\n"
"\tli $2, 4001\n"
"\tsyscall\n"
".end __start\n"
"\t.rdata\n"
"stradr: .asciiz \"hello, world!\\n\"\n"
"strlen: .word . - stradr"
);
-----------------------------------------------------------------
thank you for your previous help and hope to get more from you.
Regards
Adnan
On Fri, May 21, 2010 at 5:30 PM, Wu Zhangjin <wuzhangjin@xxxxxxxxx> wrote:
Hi,
Just found Arnaud have explained the problems, so here give you an
example I have written one year ago:
# File: hello.s -- Say Hello to MIPS Assembly Language Programmer
# Author: falcon <wuzhangjin@xxxxxxxxx>, 2009/01/17
# Ref:
# [*] http://www.tldp.org/HOWTO/Assembly-HOWTO/mips.html
# [*] MIPS Assembly Language Programmer's Guide
# [*] See MIPS Run Linux(second version)
# Compile:
# $ gcc -o hello hello.s
# or
# $ as -o hello.o hello.s
# $ ld -e main -o hello hello.o
.text
.globl main
main:
.set noreorder
.cpload $gp # setup the pointer to global data
.set reorder
# print sth. via sys_write
li $a0, 1 # print to standard ouput
la $a1, stradr # set the string address
lw $a2, strlen # set the string length
li $v0, 4004 # index of sys_write:
# __NR_write in /usr/include/asm/unistd.h
syscall # causes a system call trap.
# exit via sys_exit
move $a0, $0 # exit status as 0
li $v0, 4001 # index of sys_exit
# __NR_exit in /usr/include/asm/unistd.h
syscall
.rdata
stradr: .asciiz "hello, world!\n"
strlen: .word . - stradr # current address - the string address
# end
Regards,
Wu Zhangjin
On Fri, 2010-05-21 at 16:46 +0500, adnan iqbal wrote:
> Hi all,
>
> I am trying to compile/link/execute following very simple program in
> debian/MIPS (Tried on Qemu and Octeon). I am getting errors while
> executing the program. gdb also shows a strange behavior showing
> program entrypoint somehere in data segement. Any help getting this
> sorted out shall be appreciated.
>
> Regards
> Adnan
>
> Commands used to compile/link
> ----------------------------------------------------
> $ as hello.s -o hello.o
> $ld hello.o -o hello
> $ ./hello
>
>
> The code
> ---------------
> .data
> str:
> .asciiz "hello world\n"
> .text
> .globl __start
>
> __start:
> jal f2
> la $4,str
> li $2,4
> syscall
>
> ## terminate program via _exit () system call
> li $2, 10
> syscall
> f2:
> add $8,$8,$0
> jr $31
>
